ARTICLE IN PRESS Precambrian Research xxx (2012) xxx xxx
|
|
- Laura Harmon
- 5 years ago
- Views:
Transcription
1 Precambrian Research xxx (2012) xxx xxx Contents lists available at SciVerse ScienceDirect Precambrian Research journa l h omepa g e: Subduction related tectonic evolution of the Neoarchean eastern Dharwar Craton, southern India: New geochemical and isotopic constraints M. Ram Mohan a,, Stephen J. Piercey b, Balz S. Kamber c, D. Srinivasa Sarma a a CSIR National Geophysical Research Institute, Hyderabad 7, India b Department of Earth Sciences, Memorial University of Newfoundland, St. Johns, NL A1B 3X5, Canada c School of Natural Sciences, Trinity College Dublin, Dublin 2, Ireland a r t i c l e i n f o Article history: Received 1 November 2011 Received in revised form 9 June 2012 Accepted 20 June 2012 Available online xxx Keywords: Dharwar Craton Geochemistry Radiogenic isotopes Crustal recycling Subduction a b s t r a c t The Neoarchean eastern Dharwar Craton (EDC) is distinct from the Mesoarchean western Dharwar Craton (WDC) in many aspects of its geology. The important distinguishing features of the EDC are the predominance of younger granitoids, abundance of gold mineralization and the exposure at lower crustal depths. No consensus exists on evolutionary models for EDC; mutually exclusive plume and subduction-derived tectonic models have been proposed. Geochemical and radiogenic isotopic studies on the granitoids and volcanic rocks of three greenstone belts along a cross-section in the northern part of EDC are presented herein. The evolved Nd isotopic signatures, radiogenic Pb isotopic ratios and arc-like geochemical signatures are suggestive of a subduction regime and the involvement of recycled older crust in the derivation of these rocks. The proposed petrogenetic mechanism involves multi stage processes in a supra subduction regime involving slab dehydration, formation of hydrous basaltic melts, and re-melting and interaction with sub-arc basaltic crust at low pressures where amphibole ± plagioclase is the dominant residual phase. There is a notable systematic decrease in the extent of older crustal involvement from west to east in the EDC. This is in concurrence with the younging of Dharwar Craton from west to east and eastward subduction. The proposed petrogenetic model can efficiently explain the variations in older crustal involvement, which is very common in other Archean cratons Elsevier B.V. All rights reserved. 1. Introduction The Neoarchean represents a key period of continental crustal growth with major tectonic assembly and stabilization of large cratonic areas such as the Superior, Yilgarn, and Dharwar cratons (Condie, 2000; Condie and Kröner, 2012). These cratons are composed predominantly of granite-greenstone successions and tonalite trondhjemite granodiorite (TTG) terranes, evolved through various geodynamic processes that were likely the product of combinations of subduction zone and plume tectonics (Abbott, 1996; Condie, 1994; Huang et al., 2012; Naqvi et al., 2006; Polat et al., 2011; Polat and Kerrich, 2001; Zhai and Santosh, 2011). Though there is considerable understanding of the crustal growth and assemblages of most of these cratons, studies integrating the temporal and petrogenetic evolution of the volcanic and plutonic rocks are very limited for many cratons, particularly so for the Dharwar Craton. The Dharwar Craton represents one of the largest cratonic masses of the Indian Shield. It is divided into two principal terrains: Corresponding author. Tel.: ; fax: address: rammohan@ngri.res.in (M.R. Mohan). the Eastern Dharwar Craton (EDC) and the Western Dharwar Craton (WDC) (Fig. 1). The EDC is different from WDC in many ways. The WDC contains mostly older gneissic rocks ( Ga) and thicker crust, the EDC has thinner crust (Gupta et al., 2003a) and is comprised of predominantly younger juvenile granitoids ( 2.52 Ga) (Chardon et al., 2011, 2002; Dey et al., 2012; Jayananda et al., 2000), and auriferous greenstone belts ( Ga) that are surrounded by variably evolved syn-kinematic granitoids (Balakrishnan and Rajamani, 1987; Naqvi, 2005; Rajamani et al., 1987). Available geochronological data for the rocks of EDC suggest that greenstone volcanism, granitoid formation, accretion and deformation occurred between 2.7 and 2.5 Ga (Chardon and Jayananda, 2008; Chardon et al., 2011; Jayananda et al., 2012; Nutman et al., 1996; Rogers et al., 2007; Sarma et al., 2012). Like other Archean cratons the evolution and assembly of the EDC has been the subject of debate with the main hypothesis favoring a plume growth model (Jayananda et al., 2000), whereas other authors favor a subduction model (Chadwick et al., 2000), or a combined model involving the combination of lateral and vertical tectonics (Manikyamba and Kerrich, 2012; Naqvi et al., 2002, 2006). The southern part of the EDC is relatively well-studied because of the presence of two well-known gold deposits (Kolar and Ramagiri). Based on the isotopic and geochemical characteristics on these /$ see front matter 2012 Elsevier B.V. All rights reserved.
2 2 M.R. Mohan et al. / Precambrian Research xxx (2012) xxx xxx Fig. 1. Generalised geological map of southern Indian Peninsula. Study areas are shown in boxes. rocks, a convergent margin setting has been proposed for its evolution (Balakrishnan et al., 1990; Zachariah et al., 1996). Geochemical and isotopic studies on the younger granitoids of southern EDC through a west to east cross-section from the Closepet granite to the eastern margin of the Kolar greenstone belt, have led workers to propose generation of these rocks from a heterogeneous mantle with predominantly juvenile additions (Jayananda et al., 2000). A depleted mantle source has been proposed for the mafic volcanic rocks of EDC (Manikyamba et al., 2004a). Some of the felsic volcanic rocks and granitoids from the northern greenstone belts of EDC have geochemical systematics similar to that of modern adakites and slab melting processes are interpreted to have been important in their genesis (Manikyamba et al., 2008, 2009; Naqvi et al., 2006, 2008; Prabhakar et al., 2009). In this paper, geochemical and isotopic data are provided for syn-kinematic granitoids, and stratigraphically well constrained felsic and mafic volcanic rocks from three major Neoarchean greenstone belts of the northern EDC, namely the Sandur, Kushtagi and Hutti belts (Fig. 1). This study also reports new major and trace element data for all rock types, as well as common Pb and Nd isotopic data for some of the felsic magmatic suites. The latter data will be used with trace element data to quantify potential crust mantle interactions, to test whether these rocks contain juvenile signatures and record juvenile crustal additions similar to the younger granitoids from the southern part of EDC (Jayananda et al., 2000), and whether or not the mantle composition is uniform throughout the EDC. The study also aims to understand the tectonic processes responsible for the petrogenesis and evolution of the EDC. Furthermore, adakite-like felsic volcanic and granitoid rocks are present in all these three greenstone belts (Naqvi et al., 2008), and an attempt is made herein to test whether these granitoids and felsic adakitic rocks display true slab melt signatures similar to modern adakites (Stern and Kilian, 1996). 2. Regional geological and tectonic framework The Dharwar Craton (DC) exposes a large section of Archean continental crust (Fig. 1). Formation and the growth of different rock suites of DC appear to have taken place in more than one billion years between 3.6 and 2.5 Ga (Radhakrishna and Naqvi, 1986). The Dharwar Craton is divided into two distinct tectonic blocks: the Western Dharwar Craton (WDC) and Eastern Dharwar Craton (EDC) (Naqvi and Rogers, 1987; Swaminath and Ramakrishnan, 1981). Swaminath et al. (1976) marked an arbitrary boundary between both the blocks parallel to the western margin of Closepet granite, which was subsequently modified to coincide with the Chitradurga boundary fault and confirmed by deep seismic sounding (Kaila et al., 1979) and by Landsat imagery (Drury and Holt, 1980). Based on the recent structural, deformational and geochronological studies, it is widely agreed that thrust zone found along the eastern margin of Chitradurga greenstone belt is the boundary between both the blocks (Chadwick et al., 2003; Chardon and
3 M.R. Mohan et al. / Precambrian Research xxx (2012) xxx xxx 3 Jayananda, 2008; Chardon et al., 2011; Jayananda et al., 2006). The WDC is largely made of older Peninsular Gneissic Complex (PGC) ( Ga) (Beckinsale et al., 1980; Bhaskar Rao et al., 1992; Meen et al., 1992) and large greenstone belts that are predominantly composed of metasedimentary rocks and komatiite tholeiitic volcanic suites (Jayananda et al., 2008; Peucat et al., 1995), whereas the EDC is dominated by calc-alkaline granitoids that are interspersed with thin and linear greenstone belts (Jayananda et al., 2000; Naqvi, 2005). Based on the close lithological similarity, structural coherence and emplacement between 2.7 and 2.5 Ga, the plutonic complex of EDC was termed as Dharwar Batholith (Chadwick et al., 2000). A summary of the comparison between both the blocks can be found in Table 1 of Naqvi and Prathap (2007). The study area is located in the northern part of EDC that constitutes a horizontal cross-section, passing from Sandur greenstone belt (SGB; Fig. 2A) in the west, through Kushtagi greenstone belt (KGB; Fig. 2B), into the Hutti-Maski greenstone belt (HMGB; Fig. 2C) in the east (Fig. 1) Sandur greenstone belt The volcano-sedimentary sequences of Sandur greenstone belt (SGB) (Fig. 1) overlaps the western marginal zone of Dharwar batholith surrounded by the mixture of older PGC (>2900 Ma) and younger anatectic granites ( 2500 Ma) (Chadwick et al., 1996). Early work on this belt suggested that it was a predominantly conformable stratigraphic sequence (Chadwick et al., 2000; Roy and Biswas, 1983), whereas other workers suggest that its tectonostratigraphy is a result of terrane accretion (Manikyamba and Kerrich, 2006; Naqvi et al., 2002). The SGB contains a diverse assemblage of tectonically juxtaposed volcanic rocks, which includes submarine pillowed low K-tholeiitic to high Mg-basalts, ultramafic schists and calc-alkaline rhyolites along with an assemblage of terrigenous and chemical sediments that includes metagreywacke, chert, banded iron formation (BIF), quartzite and shale. The high temperature-low pressure metamorphism (HT/LP) of this belt was inferred to be contemporaneous with regional deformation and granite emplacement (Chadwick et al., 1996; Roy and Biswas, 1983). The volcanic rocks for this study were collected from the Vibhutigudda Formation (Prasad et al., 1997), which is also known as eastern felsic volcanic terrain (EFVT) of the SGB (Fig. 2A; Manikyamba et al., 2008). The EFVT consists of metabasalt, felsic volcanic rocks, greywacke-carbonaceous shale polymictic conglomerate and BIF (Figs. 2A and 3; Subba Rao et al., 2001). Greywacke of the EFVT have island arc provenance and the associated carbonaceous shales are interpreted as the first cycle volcanogenic sedimentary rocks deposited in an intraoceanic arctrench complex (Manikyamba and Kerrich, 2006). Zircons from the felsic volcanic rocks of the EFVT have yielded Concordia upper intercept age of 2691 ± 18 Ma and 2658 ± 14 Ma for two samples (Nutman et al., 1996). The available SHRIMP U Pb zircon ages for the granitoids surrounding Sandur belt (2719 ± 40 Ma and 2570 ± 62 Ma) suggests prolonged Neoarchean emplacement history (Nutman et al., 1996). Based on the structural relationships, the younger Rb-Sr whole rock age of Toranagallu granite (2452 ± 50 Ma) (Bhaskar Rao et al., 1992) is interpreted as the cooling age (Nutman et al., 1996). These granitoids range from banded migmatitic gneisses to porphyritic granites, have intrusive contacts parallel to the schistosity of the belt. Based on the relative ages and deformation, these granitoids are divided into six types (Chadwick et al., 1996). Granitoids for this study were collected from working quarries from the Papinayakanahalli granite in the north and Toranagallu granite in the southern part of the belt. These are homogeneous grey granites, coarse-medium grained with enclaves of porphyritic pink-grey granite at places, however the sampling is avoided from such enclaves Kushtagi greenstone belt The Kushtagi greenstone belt (KGB) occurs in the central part of the EDC and is the northern continuation of the 400 km long Ramagiri-Hungund composite greenstone belt (Fig. 1). A shear zone passes through the centre of the belt along which numerous gold occurrences are found (Manikyamba et al., 2004b). Structural studies reveal two deformational events for this belt and the emplacement of surrounding granitoids was related to late phase of D1 transpression (Matin, 2006). No age information is available for the rocks of this belt, however U Pb zircon and titanite ages are available for the felsic volcanics and surrounding granitoids of Ramagiri belt (Balakrishnan et al., 1999), which is the southern end of Ramagiri-Hungund composite greenstone belt (Fig. 1). The emplacement age for felsic volcanics of the Ramagiri belt is 2707 ± 18 Ma and the granites surrounding the belt have the emplacement ages in the range between 2650 ± 7 Ma and 2595 ± 1 Ma (Balakrishnan et al., 1999), same crystallization ages are considered for the Kushtagi rocks for Nd and Pb isotopic calculations (Table 2). The major lithologies of this belt are metabasalt, metarhyolite and minor BIF (Figs. 2B and 3). The metabasalts are generally massive and pillowed, consist of plagioclase and pyroxene, altered to chlorite actinolite at places. The rhyolites contain quartz, soda-rich plagioclase and traces of K-feldspar-sericite. Geochemical signatures of the metabasalts suggest high-mg tholeiitic nature, whereas the felsic volcanic rocks are comparable to adakites (Naqvi et al., 2006) The interlayered basic and felsic volcanic rocks were collected from the central part of the Kushtagi belt, while the granitoids are collected from either side of the belt (Fig. 2B). The granitoids surrounding the belt are generally grey granite, display sub-vertical NW trending foliation and their intrusive relationship with the belt suggest syn-kinematic emplacement. Older gneissic enclaves are seen at places within the granitoids and sampling is avoided from such enclaves. Recent geochemical and Nd isotopic studies on the granitoids surrounding this belt suggest distinct crustal histories on either side of the belt and subsequent juxtaposition due to lateral accretion (Dey et al., 2012) Hutti-Maski greenstone belt The Hutti-Maski greenstone belt (HMGB), located in the northern part of the EDC, is currently the sole primary gold producing greenstone belt in India with an annual gold production of 3.0 tons (Mohan and Sarma, 2010). Unlike the other linear greenstone belts of EDC, the HMGB is a horseshoe-shaped, elongate belt (Fig. 1). The major lithological units are pillowed and massive metabasalt, intermediate to felsic volcanic rocks and quartz-phyric rhyolite porphyry (Figs. 2C and 3). Roy (1979) recognized three generations of folds (F1, F2 and F3), with the intrusion of granodiorite between F1 and F2. The superposition of these three fold generations is interpreted to have produced the upright cuspate structure of the greenstone belt (Roy, 1991). The western boundary of the belt is tectonically juxtaposed against the older TTG basement, whereas the northern, southern, and eastern margins are intruded by younger granitoids. Gold mineralization is controlled by steeply dipping, NNW SSE trending strike slip shear zones locally referred to as reefs (Naganna, 1987). Based on the alteration mineralogy and structural studies, the gold mineralisation is related to two tectonic events (Kolb et al., 2005). The felsic volcanic rocks have yielded a U Pb zircon crystallization age of 2587 ± 7 Ma, whereas the adjoining Kavital granitoid has yielded a U Pb zircon age of 2545 ± 7 Ma (Sarma et al., 2008). A titanite U Pb age of 2532 ± 3 Ma has also been reported for the Yelagatti granitoid (Anand and Balakrishnan,
4 4 M.R. Mohan et al. / Precambrian Research xxx (2012) xxx xxx Fig. 2. (A) Simplified geological map of Eastern Felsic Volcanic Terrain (Subba Rao et al., 2001). Inset shows the disposition of EFVT in the outline map of Sandur greenstone belt. (B) Simplified geological map of the central part of Kushtagi greenstone belt (Naqvi et al., 2006). (C) Geological map of Hutti greenstone belt (Srikantia, 1995). 2010). Recent U Pb zircon age of 2569 ± 13 Ma for the felsic volcanic rock from Buddine area further confirms the predominance of 2.57 Ga event in this area (Jayananda et al., 2012). The least altered basic and felsic volcanic rocks were collected from the central part of the belt, while two altered samples are from the 24th level of Hutti gold mine (Fig. 2C). The granitoids are from the Kavital and Yelagatti (Fig. 2C). 3. Petrographic characteristics Most of the granitoids were collected from working quarries, whereas fresh volcanic rocks lacking visible veins and alteration were sampled from outcrops. Two alteration zone samples from the Hutti underground gold mine were studied to understand the effect of alteration, but the data of these two samples are not used for any petrogenetic interpretations. The sample suite provides a comprehensive stratigraphic and temporal distribution of major lithologic units in the northern part of EDC. Sandur granitoids are chiefly composed of quartz, K-feldspar (microcline and orthoclase), and plagioclase feldspar (Fig. 4A). Biotite is the dominant mafic phase. Chlorite, sphene, epidote and zoisite are accessory minerals. Quartz and feldspar are medium grained and mostly anhedral. The granitoids of Kushtagi and Hutti have more relative abundance of plagioclase feldspar over potash feldspar (orthoclase). Amphibole, biotite, sphene and opaques are the other constituting minerals. Quartz is anhedral whereas plagioclase and K-feldspars are subhedral. Plagioclase exhibits zoning (Fig. 4B), often display polysynthetic twinning. Deformation is common and can be inferred from the breaking of feldspar grain and recrystallization and grain boundary migration of quartz. Plagioclase is saussuritized (Fig. 4C), where the cores are more saussuritized than rims in zoned plagioclase crystals. Biotite, chlorite
5 M.R. Mohan et al. / Precambrian Research xxx (2012) xxx xxx 5 Fig. 3. Stratigraphic columns for the EFVT of Sandur, Kushtagi and Hutti greenstone belts having older units at the bottom. Age data as described in the text. and epidote are other constituting minerals; titanite and magnetite are common accessories (Fig. 4D). The Sandur rhyolites are made up of quartzo-feldspathic matrix; the primary minerals being quartz, plagioclase and muscovite, often exhibits porphyritic texture. The rhyolites from the central part of Kushtagi belt are sheared resulting in the granulation of quartzo-feldspathic matrix and rotation of plagioclase phenocryst at various angles to the shear plane (Fig. 4E). Plagioclase is euhedral to subhedral showing well developed twinning and zoning. Quartz also occurs as phenocryst as well in the form of veins, while the plagioclase phenocrysts display polysynthetic twinning (Fig. 4E). Quartz is generally anhedral, display cracks that are filled with secondary minerals during deformation. The Hutti rhyolites show S C deformational fabrics and the development of quartz eye (Fig. 4F). The basic rocks are generally medium- to coarse-grained amphibolites, primarily made of hornblende, intergrown with chlorite, plagioclase and quartz. 4. Geochemistry 4.1. Analytical techniques All the samples were initially reduced in a jaw crusher, and then manually powdered in agate mortars. Major elements were analyzed by X-ray fluorescence spectroscopy (XRF) at the Ontario Geoscience Laboratories (GeoLabs), Sudbury, Ontario, Canada using fused discs. Trace elements, including the high field strength elements (HFSE) and rare earth elements (REE) were analyzed using inductively coupled plasma mass spectrometry (ICP-MS) Thermo X Series II ICP-MS instrument in the Department of Earth Sciences, Laurentian University. Sample preparation for trace element analysis involved the bomb digestion of 100 mg of sample for 72 h in HF-HNO 3 at 195 C. Fluorides were converted with HCl, followed by HNO 3. Solutions were run at 1:3000 with matrix tolerant cones at low extraction voltages. 6 Li, In, 147 Sm, Re, Bi and 235 U were used as internal standards. External drift was corrected by repeated analyses of a 1:2500 solution of BHVO-2. Instrument response was calibrated relative to two independent digestions of W-2, the preferred concentrations of which are given in the Supplementary Table 1. AGV-2 and BHVO-2 were analyzed as unknowns, the long-term reproducibility of which is reported in Supplementary Table 1. For the isotope analysis, the remaining solution of the rock digest after trace element analysis, constituting more than 98% of the original solution, was dried down and converted with HBr. Lead was purified on miniaturized anion exchange columns according to the method outlined in Kamber and Gladu (2009). Lead isotope ratios were determined by ICP-MS according to the protocol of Ulrich et al. (2010). The column eluate from the anion column was then passed over a cation column on which the REE fraction was obtained. This was passed over an LN spec column to yield a Sm-free Nd separate, which was analyzed for isotope composition using a Finnegan Triton thermal ionization mass spectrometer (TIMS) at Carleton University. No isotope dilution analysis of the Sm/Nd ratio was necessary due to the high precision and accuracy of the employed trace element protocol (Babechuk and Kamber, 2011) Alteration Various geochemical studies have established that immobile elements such as Al 2 O 3, TiO 2, Zr, Y, Nb, Ta, Sc and REE (except Ce and Eu ) are least sensitive to hydrothermal alteration and metamorphism commonly found in Archean terrains, and therefore give insight into the primary petrogenetic processes that formed rocks in ancient terrains (Humphris, 1984; Jochum et al., 1991; Piercey et al., 2002; Polat and Kerrich, 2000). In contrast, mobile elements and their ratios provide insights into the effects of alteration in Archean rocks (Kamber et al., 2002; Mohan et al., 2008). It has been shown in many studies that Zr (and other HFSE and REE) is one of the least mobile elements during regional metamorphism and hydrothermal alteration, and is mobile only under very specific conditions (e.g., acid-sulfate conditions; presence of F) (Pearce and Peate, 1995; Winchester and Floyd, 1977). Zirconium is therefore a very useful index upon which other elements can be compared to test for immobility (e.g., Fig. 5). Maclean (1990) and MacLean and Barrett (1993) had illustrated that when elements are plotted
6 Table 1 Major and trace elemental compositions for various rocks of EDC. Sample RB-1 RB-4 RB-6 RB-15 RBK-25 RBK-30 RBK-31 RBK-35 RBK-37 RBH-45 RBH-43 RBH-49 RBH-52 RB-9 RB-12 RB-14 KN-120 Location Sandur Sandur Sandur Sandur Kushtagi Kushtagi Kushtagi Kushtagi Kushtagi Hutti Hutti Hutti Hutti Sandur Sandur Sandur Sandur Rock type Rhyolite Rhyolite Rhyolite Rhyolite Rhyolite Rhyolite Rhyolite Rhyolite Rhyolite Rhyolite Rhyolite Rhyolite Rhyolite Granitoid Granitoid Granitoid Granitoid Northing Easting SiO 2 (wt.%) TiO Al 2O Fe 2O MgO MnO CaO K 2O Na 2O P 2O < <0.01 < <0.01 <0.01 <0.01 LOI Total Mg# Li (ppm) 8.40 N.A N.A N.A. N.A. N.A N.A N.A. N.A B N.A N.A N.A. N.A. N.A N.A N.A. N.A Be 1.23 N.A N.A N.A. N.A. N.A N.A N.A. N.A Sc Ti V Cr Co Ni Cu Zn Ga As 2.21 N.A N.A N.A. N.A. N.A N.A N.A. N.A Rb Sr Y Zr Nb Mo Cd Sn Sb Cs Ba La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb M.R. Mohan et al. / Precambrian Research xxx (2012) xxx xxx
7 Table 1 (Continued) Sample RB-1 RB-4 RB-6 RB-15 RBK-25 RBK-30 RBK-31 RBK-35 RBK-37 RBH-45 RBH-43 RBH-49 RBH-52 RB-9 RB-12 RB-14 KN-120 Location Sandur Sandur Sandur Sandur Kushtagi Kushtagi Kushtagi Kushtagi Kushtagi Hutti Hutti Hutti Hutti Sandur Sandur Sandur Sandur Rock type Rhyolite Rhyolite Rhyolite Rhyolite Rhyolite Rhyolite Rhyolite Rhyolite Rhyolite Rhyolite Rhyolite Rhyolite Rhyolite Granitoid Granitoid Granitoid Granitoid Lu Hf Ta W Tl Pb Th U Nb/Ta Zr/Hf B/Be (La/Yb) n Sr/Y Nb/Th Nb/U Nb/Yb Th/Yb La/Sm Eu/Eu* Zr/Zr* Hf/Hf* Ti/Ti* Nb/Nb* K 2O/Na 2O Al 2O 3/TiO Al 2O 3/Na 2O Zr/Y Nb/Y Th/Ce Sc/Y Cs/Th Sr Sample RBK-22 RBK-27 RBK-28 RBK-40 RBH-55 RBH-57 RBH-60 N-218 KN-105 KN-111 RBK-38 KN-43 RBH-44 RBH-47 RBH-42 RBH-51 Location Kushtagi Kushtagi Kushtagi Kushtagi Hutti Hutti Hutti Sandur Sandur Sandur Kushtagi Kushtagi Hutti Hutti Hutti Hutti Rock type Granitoid Granitoid Granitoid Granitoid Granitoid Granitoid Granitoid Basic Basic Basic Basic Basic Basic Basic Altered Altered Northing Gold Mine Gold Mine Easting SiO 2 (wt.%) TiO Al 2O Fe 2O MgO MnO CaO K 2O Na 2O P 2O < LOI Total Mg# Li (ppm) N.A N.A. N.A. N.A. N.A. N.A. N.A. N.A. N.A. N.A. B 1.97 N.A N.A. N.A. N.A. N.A. N.A. N.A. N.A. N.A. N.A. M.R. Mohan et al. / Precambrian Research xxx (2012) xxx xxx 7
8 Table 1 (Continued) Sample RBK-22 RBK-27 RBK-28 RBK-40 RBH-55 RBH-57 RBH-60 N-218 KN-105 KN-111 RBK-38 KN-43 RBH-44 RBH-47 RBH-42 RBH-51 Location Kushtagi Kushtagi Kushtagi Kushtagi Hutti Hutti Hutti Sandur Sandur Sandur Kushtagi Kushtagi Hutti Hutti Hutti Hutti Rock type Granitoid Granitoid Granitoid Granitoid Granitoid Granitoid Granitoid Basic Basic Basic Basic Basic Basic Basic Altered Altered Be 1.43 N.A N.A. N.A. N.A. N.A. N.A. N.A. N.A. N.A. N.A. Sc Ti V Cr Co Ni Cu Zn Ga As 0.31 N.A N.A. N.A. N.A. N.A. N.A. N.A. N.A. N.A. N.A. Rb Sr Y Zr Nb Mo Cd Sn Sb Cs Ba La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er M.R. Mohan et al. / Precambrian Research xxx (2012) xxx xxx
9 Table 1 (Continued) Sample RBK-22 RBK-27 RBK-28 RBK-40 RBH-55 RBH-57 RBH-60 N-218 KN-105 KN-111 RBK-38 KN-43 RBH-44 RBH-47 RBH-42 RBH-51 Location Kushtagi Kushtagi Kushtagi Kushtagi Hutti Hutti Hutti Sandur Sandur Sandur Kushtagi Kushtagi Hutti Hutti Hutti Hutti Rock type Granitoid Granitoid Granitoid Granitoid Granitoid Granitoid Granitoid Basic Basic Basic Basic Basic Basic Basic Altered Altered Tm Yb Lu Hf Ta W Tl Pb Th U Nb/Ta Zr/Hf B/Be (La/Yb) n Sr/Y Nb/Th Nb/U Nb/Yb Th/Yb La/Sm Eu/Eu* Zr/Zr* Hf/Hf* Ti/Ti* Nb/Nb* K 2O/Na 2O Al 2O 3/TiO Al 2O 3/Na 2O Zr/Y Nb/Y Th/Ce Sc/Y Cs/Th Sr N.A. = not analysed. M.R. Mohan et al. / Precambrian Research xxx (2012) xxx xxx 9
10 10 M.R. Mohan et al. / Precambrian Research xxx (2012) xxx xxx Fig. 4. (A F) Photomicrographs showing the mineral assemblages and textural features for the rocks of EDC. against Zr those with linear trends that pass through the origin were likely immobile, whereas those that were scattered likely represent mobile elements (e.g., Fig. 5). Bivariate plots of TiO 2, Y, La and Yb versus Zr display linear trends that pass near the origin; Nb and Th show minor scatter, but also exhibit well defined linear trends (Fig. 5A E), suggesting these elements were immobile and represent primary values. The mobile elements Pb, Cs and Tl also show linear trends (Fig. 5F H), with the exception of the two altered basalts, suggesting that these, and likely other potentially mobile elements, were also immobile and represent primary values. Furthermore, most samples have low Spitz-Darling index values (Al 2 O 3 /Na 2 O < 10; Spitz and Darling, 1978), and LOI < 3 wt.%, and there are no correlations between LOI and the immobile elements (Table 1), all suggesting that in most samples both the immobile and so-called potentially mobile elements represent near-primary values and have not been significantly modified by metamorphism and alteration Major and trace elements The geochemical data including key elemental ratios for the mafic and felsic volcanic rocks, and granitoids are presented in Table 1. Most mafic rocks have low SiO 2 (excluding the two altered samples), are primarily basalts (Fig. 6A), that are sub-alkalic (Nb/Y < 0.7), have broadly tholeiitic affinities with low Zr/Y ratios (Fig. 7A), and Mg# 50 (Fig. 7C). The mafic rocks have relatively flat to slightly LREE-enriched chondrite normalized REE patterns, and on multi-element plots both groups commonly exhibit Nb, Ti troughs with relative enrichment of LILE, consistent with an arc environment; there are two groups with varying enrichments in
11 M.R. Mohan et al. / Precambrian Research xxx (2012) xxx xxx 11 Fig. 5. (A H) Zirconium against selected element variation diagrams to demonstrate the effects of alteration. Positive correlations suggest that they were not significantly mobilized by alteration. REE and other trace elements, however (Fig. 8). The sample group with enriched trace and REE are confined to the mafic volcanic rocks of Sandur belt and different from the mafic volcanic rocks from remaining two belts (Table 1 and Fig. 8A and B). Felsic volcanic rocks and granitoids have high SiO 2 contents similar to that of rhyolites (Fig. 6A), sub-alkalic, having calc-alkaline affinities with high Zr/Y ratios (Fig. 7A; Table 1). The normative mineralogy suggests that these rocks are tonalite, trondhjemite, granodiorite and minor granite (Fig. 6B). Archean TTG are widely sub-divided into low-al and high-al varieties based on the presence and/or absence of plagioclase in the source residue (Barker and Arth, 1976); samples of this study are in both groups (Fig. 7B).
12 12 M.R. Mohan et al. / Precambrian Research xxx (2012) xxx xxx Fig. 6. (A and B) Classification plots for the rocks of EDC. Total alkalis against Silica diagram (LeBas et al., 1986; O Connor, 1965). Normative feldspar differentiation diagram (O Connor, 1965) to show the various granitoid types of EDC. All the felsic rocks (except for that of Sandur rhyolites) display Mg# of less than 50 (Fig. 7C), suggesting no substantial peridotite assimilation (Rapp et al., 1991). Though Sandur rhyolites have high Mg#, their corresponding Cr and Ni compositions are too low (Table 1) to appraise mantle hybridization for these rocks. The enrichment of Na 2 O at constant SiO 2 and the Na 2 O/K 2 O > 1 suggests potential plagioclase accumulation, but the K 2 O contents are higher for Sandur samples relative to those of Kushtagi and Hutti (Table 1). The primitive mantle-normalized patterns (Sun and McDonough, 1989) display negative anomalies of certain high field strength elements (HFSE) such as Nb, Ti, but positive Zr, Al anomalies, and depletions in compatible elements (Fig. 8D and F). The HFSE depletions are common in rocks derived from arc environments, those that have interacted with continental crust, or those who have crystallized Ti-rich phases (Foley et al., 2000). All the felsic rocks have variably fractionated REE patterns with consistent LREE-enrichment and HREE depletions (Fig. 8C and E). General negative relationship between Eu anomaly and REE fractionation is suggestive of plagioclase accumulation and variable depths of melting. Among all, the Hutti rhyolites display relatively variable REE systematics, which Fig. 7. (A) Zr/Y vs. Y diagram to differentiate magmatic affinities (Barrett and MacLean, 1999). (B) Al 2O 3 SiO 2 diagram for classifying different types of TTG (Barker and Arth, 1976). (C) SiO 2 Mg# plot to demonstrate that very few felsic rocks of EDC had undergone significant mantle assimilation (after Rapp et al., 1999). could be due to the hydrothermal activity associated with gold mineralisation. The Sandur felsic magmatic rocks have greater REE and trace elemental abundances when compared to Kushtagi and Hutti (Fig. 8C F). Sandur granitoids show a negative Eu anomaly, suggesting plagioclase fractionation, while the remaining samples display mild positive to negative Eu anomalies, which, like the elevated Na, may be due to the accumulation of plagioclase in the melt (Foley et al., 2000) as evident by the presence of plagioclase phenocrysts (Fig. 4).
13 M.R. Mohan et al. / Precambrian Research xxx (2012) xxx xxx Isotopes Neodymium and Pb isotopic data are presented in Table Nd isotopes Initial Nd isotope ratios were calculated using the available U Pb zircon ages for the same lithostratigraphic units from the corresponding greenstone belts. The initial Nd values were calculated assuming CHUR (Chondrite uniform reservoir) 143 Nd/ 144 Nd = similar to that of the model depleted mantle (Goldstein et al., 1984) and 147 Sm/ 144 Nd = (Jacobsen and Wasserburg, 1980). It has been suggested that Nd and Pb isotopic ratios can be affected due to the hydrothermal fluid activity or due to post-crystallization effects (Prior et al., 1999; Verma et al., 2005), and such disturbances are more evident in lithologies of many Archean gold bearing greenstone belts, like at Kolar (Krogstad et al., 1995) and Ramagiri (Zachariah et al., 1995) of the Dharwar craton. Neodymium and Pb isotopic signatures of some of the felsic volcanic rocks from the Hutti greenstone belt display such alteration-related changes (Table 2), hence these samples were eliminated from further interpretations. The mafic rocks from Hutti display positive initial Nd values that range between +1.9 and +2.9, typical of Neoarchean depleted mantle (Shirey and Hanson, 1986), implying formation from depleted mantle sources (Anand and Balakrishnan, 2010). In contrast, the granitoids and rhyolites have predominantly negative initial Nd values ranging from +0.3 to 7.5 and 2.2 to 6.1, respectively (Table 2) consistent with involvement of variable amount of short-lived juvenile crust to ancient crust in their genesis (Fig. 9A). The depleted mantle model ages (T DM ) calculated for those with 147 Sm/ 144 Nd < 0.15, range from 2600 to 3200 Ma (Table 2). When the Nd model ages are plotted against the corresponding crystallization ages (Fig. 9B), the samples are distributed into three main clusters, where three samples that have <100 Ma difference between the Nd model and crystallization ages are considered as juvenile (Tomlinson et al., 2004), and the remaining evolved samples broadly coincide with the two major crystallization events of the basement rocks of WDC at Ma and Ma (Taylor et al., 1984) Pb isotopes The Pb isotopic system is more sensitive in detecting the nature of ancient crust because the half-lives of 235 U and 238 U are shorter than those of 147 Sm; hence, the difference in concentration between mantle and crust is much larger for Pb than for Nd. In general, the Dharwar felsic rocks have elevated Pb isotopic ratios ( 207 Pb/ 204 Pb ) compared to modeled 2.7 Ga Archean mantle ( 207 Pb/ 204 Pb 14.42; Kramers and Tolstikhin (1997). The granitoids are relatively more radiogenic and have variable Pb isotopic ratios than the rhyolites (Table 2). There is a spatial variation in the Pb isotopic ratios with the westernmost Sandur samples being most radiogenic and with systematic decrease in Pb isotopic ratios eastward through the Kushtagi and Hutti belts. 6. Discussion 6.1. Mantle source characteristics and tectonic setting of basaltic rocks in the EDC Felsic volcanic rocks are abundant in the greenstone successions of EDC. The complexity of genetic models proposed for Archean rhyolite and surrounding TTG (Martin et al., 2005; Polat and Kerrich, 2002; Smithies, 2000) often creates ambiguity when trying to understand the role of juvenile additions in greenstone sequences, Table 2 Nd and Pb isotopic compositions of the rocks of EDC. 206 Pb/ 204 Pb ± 207 Pb/ 204 Pb ± 208 Pb/ 204 Pb ± T DM (Ga) Sample Rock type Area Age (Ma) Nd (ppm) Sm (ppm) 147 Sm/ 144 Nd 143 Nd/ 144 Nd Ndt RBH-43 Rhyolite Hutti 2587 a (7) RBH-45 Rhyolite Hutti 2587 a (10) RBH-52 Rhyolite Hutti 2587 a (8) RB-1 Rhyolite Sandur 2691 b (8) RB-6 Rhyolite Sandur 2691 b (9) RB-15 Rhyolite Sandur 2691 b (7) RBK-25 Rhyolite Kushtagi 2707 c (8) RBK-30 Rhyolite Kushtagi 2707 c (8) RBK-31 Rhyolite Kushtagi 2707 c (30) RBH-55 Granitoid Hutti 2545 a (10) RBH-57 Granitoid Hutti 2545 a (10) RBH-60 Granitoid Hutti 2545 a (10) RB-14 Granitoid Sandur 2570 b (8) KN-120 Granitoid Sandur 2570 b (8) RBK-22 Granitoid Kushtagi 2650 c (11) RBK-28 Granitoid Kushtagi 2650 c (8) RBK-40 Granitoid Kushtagi 2650 c (8) RBH-44 Basic Hutti 2587 a (10) RBH-47 Basic Hutti 2587 a (10) Source for age data: a Sarma et al., 2008; b Nutman et al., 1996; c Balakrishnan et al., 1999.
LATE ARCHAEAN FELSIC ALKALINE MAGMATISM: GEOLOGY, GEOCHEMISTRY, AND TECTONIC SETTING
LATE ARCHAEAN FELSIC ALKALINE MAGMATISM: GEOLOGY, GEOCHEMISTRY, AND TECTONIC SETTING ZOZULYA DMITRY 1, EBY NELSON 2 1 - Geological Institute Kola Science Centre RAS, Apatity, Russia 2 - Department of Environmental,
More informationDiscrimination between Archean A-type granitoids and sanukitoid suites using tectonic setting, geochemistry, and fertility type
Discrimination between Archean A-type granitoids and sanukitoid suites using tectonic setting, geochemistry, and fertility type ZOZULYA DMITRY 1, EBY NELSON 2 1 - Geological Institute Kola Science Centre
More informationCHAPTER VI CONCLUSIONS
CHAPTER VI CONCLUSIONS In this Chapter, salient observations made in understanding the various tectonothermal events, including U-Pb in-situ monazite geochronology of Sargur schists and granulites exposed
More informationArchean Terranes. Archean Rocks. Southeastern Africa. West Greenland. Kaapvaal Craton. Ancient Gneiss Complex
Archean Terranes Archean Rocks Chapter 15A >2.5 Gy old Younger supracrustal sequences Greenstone belts Calc-alkaline metavolcanic rocks Older gneiss complexes Quartzo-feldspathic rocks Tonalites and migmatites
More informationWorked Example of Batch Melting: Rb and Sr
Worked Example of Batch Melting: Rb and Sr Basalt with the mode: Table 9.2. Conversion from mode to weight percent Mineral Mode Density Wt prop Wt% ol 15 3.6 54 0.18 cpx 33 3.4 112.2 0.37 plag 51 2.7 137.7
More informationCHAPTER 8 SUMMARY AND CONCLUSIONS
CHAPTER 8 SUMMARY AND CONCLUSIONS The Aravalli Mountain Range (AMR) is the main edifice of NW Indian shield. It is about 800 km long and 200 km wide with NE-SW strike. The rocks of AMR are hosted in an
More informationGSA DATA REPOSITORY
GSA DATA REPOSITORY 2013011 Chen et al. ANALITICAL METHODS Microprobe analysis Microprobe analyses of minerals were done on a JEOL Superprobe JXA 8100 at the Key Laboratory of Orogenic Belts and Crustal
More informationGSA Data Repository
GSA Data Repository 218145 Parolari et al., 218, A balancing act of crust creation and destruction along the western Mexican convergent margin: Geology, https://doi.org/1.113/g39972.1. 218145_Tables DR1-DR4.xls
More informationBreeding et al., Data Repository Material Figure DR1. Athens. Study Area
Breeding, Ague, and Brocker 1 Figure DR1 21 o 24 Greece o A 38 o Athens Tinos 37 o Syros Attic-Cycladic Blueschist Belt Syros Kampos B Study Area Ermoupoli N Vari Unit Cycladic HP-LT Unit Marble horizons
More information2 Britain s oldest rocks: remnants of
Britain s oldest rocks: remnants of Archaean crust 15 2 Britain s oldest rocks: remnants of Archaean crust 2.1 Introduction Owing to the complex nature of extremely old deformed rocks, the standard methods
More informationGeochemistry of Permian rocks of the Yukon-Tanana terrane, western Yukon: GEM 2 Cordillera project
GEOLOGICAL SURVEY OF CANADA OPEN FILE 8170 Geochemistry of Permian rocks of the Yukon-Tanana terrane, western Yukon: GEM 2 Cordillera project D. Milidragovic, J.J. Ryan, A. Zagorevski, S.J. Piercey 2016
More informationPetrogenetic Constraints at Mount Rainier Volcano, Washington
Petrogenetic Constraints at Mount Rainier Volcano, Washington S. C. Kuehn and P. R. Hooper, Department of Geology, Washington State University, Pullman, WA A. E. Eggers and C. Kerrick, Department of Geology,
More informationPetrology and Geochronology of Iran Tepe volcano, Eastern Rhodopes, Bulgaria: Age relationship with the Ada Tepe gold deposit. (preliminary data)
Petrology and Geochronology of Iran Tepe volcano, Eastern Rhodopes, Bulgaria: Age relationship with the Ada Tepe gold deposit. (preliminary data) Peter Kibarov, Peter Marchev, Maria Ovtcharova, Raya Raycheva,
More informationIMSG Post-conference Field Guide
IMSG 2017 - Post-conference Field Guide Jérémie Lehmann, Marlina Elburg and Trishya Owen-Smith The purpose of this short field excursion on Wednesday 18 January is to show a variety of rocks that make
More informationGeochemistry of Mafic Dykes of Chittoor District, Andhra Pradesh, Southern India
http://www.e-journals.in Chemical Science Transactions DOI:10.7598/cst2014.822 2014, 3(3), 953-960 RESEARCH ARTICLE Geochemistry of Mafic Dykes of Chittoor District, Andhra Pradesh, Southern India D. B.
More informationSpot Name U-Pb ages (Ma) Plagioclase ages (Ma) Biotite age (Ma) Whole rock age (Ma)
Table 1. Average U-Pb ages from this study in comparison with previous ages from Sherrod and Tosdal (1991, and references therein). Previous study ages are reported as ranges including uncertainty (i.e.
More informationTrace Elements. Today s lecture
Trace Elements 300 Ni 200 ppm 100 0 300 Zr 200 100 0 40 50 60 70 80 SiO 2 wt. % Updates: M&M due date: Tuesday Today s lecture Topics: Trace element compositions Trace element behavior Partitioning Spider(
More informationREE Geochemistry of ore zones in the Archean auriferous schist belts of the eastern Dharwar Craton, south India
REE Geochemistry of ore zones in the Archean auriferous schist belts of the eastern Dharwar Craton, south India T S Giritharan and V Rajamani School of Environmental Sciences, Jawaharlal Nehru University,
More informationEvolution of the Slave Province and Abitibi Subprovince Based on U-Pb Dating and Hf Isotopic Composition of Zircon
Evolution of the Slave Province and Abitibi Subprovince Based on U-Pb Dating and Hf Isotopic Composition of Zircon John W.F. Ketchum 1, Wouter Bleeker 2, William L. Griffin 1, Suzanne Y. O Reilly 1, Norman
More informationpredictive iscovery Why is the gold where it is? redictive mineral ineral discovery pmd CRC
The Y2 project (2001-2004) Time-space evolution of the Yilgarn Craton: implications for geodynamics Kevin Cassidy and the Y2 team Reduced D Risk through Improved Targeting ineral d Why is the gold where
More informationGEOL 3313 Petrology of Igneous and Metamorphic Rocks Study Guide for Final Examination Glen Mattioli
GEOL 3313 Petrology of Igneous and Metamorphic Rocks Study Guide for Final Examination Glen Mattioli Chapter 5: Crystal-Melt phase diagrams Effect of water pressure on feldspar stability Hypersolvus vs.
More informationSecular Archaean. Pronounced secular trends from. However, also. Cr, intermediate to felsic magmas, and
Secular Archaean Pronounced secular trends from 1. early sodic granites (TTGs) 2. later potassic granites However, also 1. LILE- & LREE-enriched, high MgO, Mg#, Ni, Cr, intermediate to felsic magmas, and
More informationREGOLITH GEOCHEMISTRY OF THE NORTH KIMBERLEY, WESTERN AUSTRALIA: A STRONG PROXY FOR BEDROCK
REGOLITH GEOCHEMISTRY OF THE NORTH KIMBERLEY, WESTERN AUSTRALIA: A STRONG PROXY FOR BEDROCK Paul A. Morris 1 1 Geological Survey of Western Australia, 100 Plain Street, East Perth 6004, Western Australia;
More informationGLY 155 Introduction to Physical Geology, W. Altermann. Grotzinger Jordan. Understanding Earth. Sixth Edition
Grotzinger Jordan Understanding Earth Sixth Edition Chapter 4: IGNEOUS ROCKS Solids from Melts 2011 by W. H. Freeman and Company Chapter 4: Igneous Rocks: Solids from Melts 1 About Igneous Rocks Igneous
More informationSummary of test results for Daya Bay rock samples. by Patrick Dobson Celia Tiemi Onishi Seiji Nakagawa
Summary of test results for Daya Bay rock samples by Patrick Dobson Celia Tiemi Onishi Seiji Nakagawa October 2004 Summary A series of analytical tests were conducted on a suite of granitic rock samples
More informationFigure GS-25-1: General geology and domain subdivisions in northwestern Superior Province. 155
GS-25 ASSEAN LAKE ANCIENT CRUST: AN UPDATE by M.T. Corkery, Ch.O. Böhm 1 and L.M Heaman 1 Corkery, M.T., Böhm, Ch.O. and Heaman, L.M. 2000: Assean Lake ancient crust: an update; in Report of Activities
More informationCaracterísticas e Critérios da Exploração de Depósitos Orogenéticos de Ouro
Características e Critérios da Exploração de Depósitos Orogenéticos de Ouro Richard Goldfarb, goldfarb@usgs.gov, SIMEXMIN 2012 Archean Lode Gold Deposits Greenstone Belts in granitoid-greenstone terranes
More informationINTRODUCTION. Basalt, the widespread igneous rock on the earth sur-face. today appear to have been equally important
INTRODUCTION Basalt, the widespread igneous rock on the earth sur-face today appear to have been equally important in the geologic past. Basaltic rocks are mostly partial melting products of the upper
More informationChapter - IV PETROGRAPHY. Petrographic studies are an integral part of any structural or petrological studies in
Chapter - IV PETROGRAPHY 4.1. Introduction Petrographic studies are an integral part of any structural or petrological studies in identifying the mineral assemblages, assigning nomenclature and identifying
More informationGEOL 2312 Igneous and Metamorphic Petrology Spring 2016 Score / 58. Midterm 1 Chapters 1-10
GEOL 2312 Igneous and Metamorphic Petrology Name KEY Spring 2016 Score / 58 Midterm 1 Chapters 1-10 1) Name two things that petrologists want to know about magmas (1 pt) Formation, source, composition,
More informationThe mantle metasomatism: diversity and impact What the mantle xenoliths tell us?
The mantle metasomatism: diversity and impact What the mantle xenoliths tell us? Mantle metasomatism Physical and chemical processes that are implemented during the flow of magmas and / or fluids within
More informationIgneous and Metamorphic Rock Forming Minerals. Department of Geology Mr. Victor Tibane SGM 210_2013
Igneous and Metamorphic Rock Forming Minerals Department of Geology Mr. Victor Tibane 1 SGM 210_2013 Grotzinger Jordan Understanding Earth Sixth Edition Chapter 4: IGNEOUS ROCKS Solids from Melts 2011
More informationLecture 38. Igneous geochemistry. Read White Chapter 7 if you haven t already
Lecture 38 Igneous geochemistry Read White Chapter 7 if you haven t already Today. Magma mixing/afc 2. Spot light on using the Rare Earth Elements (REE) to constrain mantle sources and conditions of petrogenesis
More informationTABLE DR2. Lu-Hf ISOTOPIC DATA FOR WHOLE ROCK SAMPLES AND ZIRCONS [Lu] [Hf]
TABLE DR1. LOWER CRUSTAL GRANULITE XENOLITH DERIVATION AND MINERALOGY Sample Kimberlite Type Mineralogy KX1-1 Lace s gt + qz + sa + rt (sil, ky, gr, su, cor, zr, mz) KX1-2 Lace s gt + sa + qz + rt (sil,
More informationThe Composition of the Continental Crust
The Composition of the Continental Crust Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Apollo 17 view of Earth Rationale: Why is studying crust composition important?
More informationGeochemical analysis unveils frictional melting process in a
GSA Data Repository 219116 1 2 3 Geochemical analysis unveils frictional melting process in a subduction zone fault Tsuyoshi Ishikawa and Kohtaro Ujiie 4 Supplemental Material 6 7 8 9 METHOD TABLES (Tables
More information1 Potassic adakite magmas and where they come from: a mystery solved?
1 Potassic adakite magmas and where they come from: a mystery solved? 2 3 John Clemens Kingston University (London) Long Xiao China University of Geosciences (Wuhan) 4 Adakites are volcanic and intrusive
More informationBird River Belt in southeastern Manitoba: a Neoarchean volcanic arc in the Western Superior Province. Paul Gilbert Manitoba Geological Survey
Bird River Belt in southeastern Manitoba: a Neoarchean volcanic arc in the Western Superior Province Paul Gilbert Manitoba Geological Survey Location of Bird River Belt Bird River Belt Winnipeg Bird River
More informationChang Wenbo.
The spatial and temporal distributions of the late Mesozoic volcanic successions in the Changling fa ult depression of the Songliao Basin, NE China, and their controlling effects Chang Wenbo susanna0703@163.com
More informationCarbonatites to Alkali Granites Petrogenetic Insights from the Chilwa and Monteregian Hills-White Mountain Igneous Provinces
Carbonatites to Alkali Granites Petrogenetic Insights from the Chilwa and Monteregian Hills-White Mountain Igneous Provinces G. Nelson Eby Department of Environmental, Earth, & Atmospheric Sciences University
More informationEssentials of Geology, 11e
Essentials of Geology, 11e Igneous Rocks and Intrusive Activity Chapter 3 Instructor Jennifer Barson Spokane Falls Community College Geology 101 Stanley Hatfield Southwestern Illinois College Characteristics
More informationBulyanhulu: Anomalous gold mineralisation in the Archaean of Tanzania. Claire Chamberlain, Jamie Wilkinson, Richard Herrington, Ettienne du Plessis
Bulyanhulu: Anomalous gold mineralisation in the Archaean of Tanzania Claire Chamberlain, Jamie Wilkinson, Richard Herrington, Ettienne du Plessis Atypical Archaean gold deposits Groves et al., 2003 Regional
More informationRegional geology of study areas 3
1 Introduction Central part Indonesia geographically is including Kalimantan, Sulawesi and Java islands. Accretionary and metamorphic complexes expose in the Central Java, South Kalimantan and South Central
More informationRare Earth Elements in some representative arc lavas
Rare Earth Elements in some representative arc lavas Low-K (tholeiitic), Medium-K (calc-alkaline), and High-K basaltic andesites and andesites. A typical N-MORB pattern is included for reference Notes:
More informationLecture 5 Sedimentary rocks Recap+ continued. and Metamorphic rocks!
Lecture 5 Sedimentary rocks Recap+ continued and Metamorphic rocks! Metamorphism Process that leads to changes in: Mineralogy Texture Sometimes chemical composition Metamorphic rocks are produced from
More informationPETROGENESIS OF A GRANITE XENOLITH IN THE 1.1 GA MIDCONTINENT RIFT AT SILVER BAY, MN
PETROGEESIS OF A GRAITE XEOLITH I THE 1.1 GA MIDCOTIET RIFT AT SILVER BAY, M ATALIE JUDA Macalester College Sponsor: Karl Wirth ITRODUCTIO Much of the study of the orth American 1.1 Ga Keweenawan Midcontinent
More informationPETROGENESIS OF A SERIES OF MAFIC SHEETS WITHIN THE VINALHAVEN PLUTON, VINALHAVEN ISLAND, MAINE
PETROGENESIS OF A SERIES OF MAFIC SHEETS WITHIN THE VINALHAVEN PLUTON, VINALHAVEN ISLAND, MAINE DANIEL HAWKINS Western Kentucky University Research Advisor: Andrew Wulff INTRODUCTION Round Point, in the
More informationMACRORYTHMIC GABBRO TO GRANITE CYCLES OF CLAM COVE VINALHAVEN INTRUSION, MAINE
MACRORYTHMIC GABBRO TO GRANITE CYCLES OF CLAM COVE VINALHAVEN INTRUSION, MAINE NICK CUBA Amherst College Sponsor: Peter Crowley INTRODUCTION The rocks of the layered gabbro-diorite unit of the Silurian
More informationIgneous Rock Classification, Processes and Identification Physical Geology GEOL 100
Igneous Rock Classification, Processes and Identification Physical Geology GEOL 100 Ray Rector - Instructor Major Concepts 1) Igneous rocks form directly from the crystallization of a magma or lava 2)
More informationU-Pb Isotope Studies on Titanites and Zircons
CHAPTER -4 U-Pb Isotope Studies on Titanites and Zircons from the Granitoids surrounding the Hutti Schist Belt of the Eastern Dharwar Craton U-Pb ISOTOPE STUDIES ON TITANITES AND ZIRCONS FROM THE GRANITOIDS
More informationTopics Laramide Orogeny: Late Cretaceous to Early Eocene Reading: GSA DNAG volume 3, Ch. 6
Topics Laramide Orogeny: Late Cretaceous to Early Eocene Reading: GSA DNAG volume 3, Ch. 6 Late Cretaceous to early Eocene New patterns developed 5 main regions Tectonic interpretations Post-Laramide events
More informationLab: Metamorphism: minerals, rocks and plate tectonics!
Introduction The Earth s crust is in a constant state of change. For example, plutonic igneous rocks are exposed at the surface through uplift and erosion. Many minerals within igneous rocks are unstable
More informationXM1/331 XM1/331 BLFX-3 XM1/331
a b AkC AkC strontian fluoro-apatite clinopyroxene phlogopite K-richterite XM1/331 clinopyroxene XM1/331 Fe-Ti ox c d clinopyroxene kric AkC ilmenite Sr-barite AkC XM1/331 BLFX-3 Supplementary Figure 1.
More informationEvaluating the Intrusion-Related Model for the Archean Low-Grade, High- Tonnage Côté Gold Au(-Cu) Deposit
Evaluating the Intrusion-Related Model for the Archean Low-Grade, High- Tonnage Côté Gold Au(-Cu) Deposit L.R. Katz, D.J. Kontak, Laurentian University, B. Dubé, V. McNicoll, Geological Survey of Canada
More informationTowards a tectonic framework for the Gawler Craton. Martin Hand Justin Payne, Greg Swain, Karin Barovich, Rian Dutch, Anthony Reid, Mike Schwarz
Martin Hand Justin Payne, Greg Swain, Karin Barovich, Rian Dutch, Anthony Reid, Mike Schwarz The tectonic evolution of is defined by two periods of tectonism both of which lead to apparent cratonisation.
More informationANALYTICAL METHODS AND RESULTS
ANALYTICAL METHODS AND RESULTS 4.1 Analytical Methods Geochemical analysis involves many steps from powdering of rock samples to dissolutions and finally analysis. 5 to 10 kg of fresh samples were collected
More informationPrecambrian Research
Precambrian Research 182 (2010) 43 56 Contents lists available at ScienceDirect Precambrian Research journal homepage: www.elsevier.com/locate/precamres Geochemistry of TTG and TTG-like gneisses from Lushan-Taihua
More information"When Gregor Samsa woke up one morning from unsettling dreams, he found himself changed into a monstrous bug. Metamorphosis, by Franz Kafka
Metamorphosis "When Gregor Samsa woke up one morning from unsettling dreams, he found himself changed into a monstrous bug. Metamorphosis, by Franz Kafka Metamorphism The transformation of rock by temperature
More informationRegional Geochemical Mapping in the Caledonides of southeast Ireland
Regional Geochemical Mapping in the Caledonides of southeast Ireland Patrick O Connor & Vincent Gallagher Geological Survey of Ireland GSI Regional Geochemical Mapping Programme Inishowen 1985 200 stream
More informationPlate tectonics, rock cycle
Dikes, Antarctica Rock Cycle Plate tectonics, rock cycle The Rock Cycle A rock is a naturally formed, consolidated material usually composed of grains of one or more minerals The rock cycle shows how one
More informationGEOLOGICAL INVESTIGATION IN THE ISLAND LAKE GREENSTONE BELT, NORTHWESTERN SUPERIOR PROVINCE, MANITOBA (PARTS OF NTS 53E/15 & 16) GS-18
GS-18 GEOLOGICAL INVESTIGATION IN THE ISLAND LAKE GREENSTONE BELT, NORTHWESTERN SUPERIOR PROVINCE, MANITOBA (PARTS OF NTS 53E/15 & 16) by S. Lin, H.D.M. Cameron, E.C. Syme and F. Corfu 1 Lin, S., Cameron,
More informationPUBLICATIONS. Geochemistry, Geophysics, Geosystems
PUBLICATIONS Geochemistry, Geophysics, Geosystems RESEARCH ARTICLE Key Points: Source and magma mixing processes are evident in continental subduction factory The heterogeneous mantle source is generated
More informationChapter 4 Rocks & Igneous Rocks
Chapter 4 Rocks & Igneous Rocks Rock Definition A naturally occurring consolidated mixture of one or more minerals e.g, marble, granite, sandstone, limestone Rock Definition Must naturally occur in nature,
More informationThe Genesis of Kurišková U-Mo ore deposits. Rastislav Demko, Štefan Ferenc, Adrián Biroň, Ladislav Novotný & Boris Bartalský
The Genesis of Kurišková U-Mo ore deposits Rastislav Demko, Štefan Ferenc, Adrián Biroň, Ladislav Novotný & Boris Bartalský Kurišková project development Uranium (uranium ore) has higher value in comparison
More informationOverview of the KAHT system. Ian E.M. Smith, School of Environment, University of Auckland
Overview of the KAHT system Ian E.M. Smith, School of Environment, University of Auckland Tonga-Kermadec-New Zealand Arc Developed on the Pacific - Australian convergent margin Mainly intraoceanic except
More informationGY 112 Lecture Notes Archean Geology
GY 112 Lecture Notes D. Haywick (2006) 1 GY 112 Lecture Notes Archean Geology Lecture Goals: A) Time frame (the Archean and earlier) B) Rocks and tectonic elements (shield/platform/craton) C) Tectonics
More informationMetamorphic history of Nuvvuagittuq greenstone belt, Northeastern Superior Province, Northern Quebec, Canada
Metamorphic history of Nuvvuagittuq greenstone belt, Northeastern Superior Province, Northern Quebec, Canada By: Majnoon, M., Supervisor: Minarik, W.G., Committee members: Hynes, A., Trzcienski, W.E. 1.
More informationPrecambrian Research
Precambrian Research 183 (2010) 635 659 Contents lists available at ScienceDirect Precambrian Research journal homepage: www.elsevier.com/locate/precamres Paleoproterozoic gabbronoritic and granitic magmatism
More informationEMMR25 Mineralogy: Ol + opx + chlorite + cpx + amphibole + serpentine + opaque
GSA Data Repository 2017365 Marshall et al., 2017, The role of serpentinite derived fluids in metasomatism of the Colorado Plateau (USA) lithospheric mantle: Geology, https://doi.org/10.1130/g39444.1 Appendix
More informationMist Mis y Lake y Lak Mapping Progr ogr
Far North Geomapping Initiative: Preliminary Results From Geological Mapping in the Misty Lake Area, Northwestern Manitoba Paul Kremer, Chris Couëslan, Anders Carlson (MGS) Nicole Rayner (GSC) Misty Lake
More informationChapter 5 WHOLE-ROCK MAJOR AND TRACE ELEMENTS GEOCHEMISTRY
Chapter 5 WHOLE-ROCK MAJOR AND TRACE ELEMENTS GEOCHEMISTRY 5.1 Introduction All samples were affected by extensive post-magmatic alteration, partially responsible for the relatively high LOI (i.e., loss
More informationMagma fertility: Concepts and JCU research at NQ
Magma fertility: Concepts and JCU research at NQ Zhaoshan Chang*, Carl Spandler, Yanbo Cheng EGRU, JCU *Zhaoshan.chang@jcu.edu.au 27 May 2015 Townsville, Queensland, Australia Magma fertility Miners dream
More informationThe 2740 Ma Côté Gold Au(-Cu) deposit, Canada: Example of porphyry-type magmatic-hydrothermal ore-forming processes in the Archean
The 2740 Ma Côté Gold Au(-Cu) deposit, Canada: Example of porphyry-type magmatic-hydrothermal ore-forming processes in the Archean Daniel J. Kontak, Laura Katz, Laurentian University Benoit Dubé, Geological
More informationIgneous Rocks. Sedimentary Rocks. Metamorphic Rocks
Name: Date: Igneous Rocks Igneous rocks form from the solidification of magma either below (intrusive igneous rocks) or above (extrusive igneous rocks) the Earth s surface. For example, the igneous rock
More informationRegional and local variations in geochemistry and tectonics along and across Central America
Regional and local variations in geochemistry and tectonics along and across Central America Michael J. Carr, Department of Geological Sciences, Wright Lab Rutgers University, 610 Taylor Rd., Piscataway
More informationEXISTING GEOLOGICAL INFORMATION
CHAPER 3 EXISTING GEOLOGICAL INFORMATION 3-1 General Geology of the Surrounding Area (1) General geology and ore deposits in Mongolia Geographically, Mongolia is a country located between Russia to the
More informationEvolution of the Malko Tarnovo plutonism and its significance for the formation of the ore deposits in the region.
Evolution of the Malko Tarnovo plutonism and its significance for the formation of the ore deposits in the region. R. Nedialkov, B. Kamenov, B. Mavroudchiev, E. Tarassova, M. Popov Introduction The Malko
More informationGEOCHEMICAL FOOTPRINTS OF IOCG DEPOSITS BENEATH THICK COVER: INSIGHTS FROM THE OLYMPIC CU-AU PROVINCE, SOUTH AUSTRALIA
GEOCHEMICAL FOOTPRINTS OF IOCG DEPOSITS BENEATH THICK COVER: INSIGHTS FROM THE OLYMPIC CU-AU PROVINCE, SOUTH AUSTRALIA Adrian Fabris 12, Simon van der Wielen 23, Tim Keeping 12, Georgina Gordon 12 1 Geological
More informationChapter 7 Metamorphism, Metamorphic Rocks, and Hydrothermal Rocks
Chapter 7 Metamorphism, Metamorphic Rocks, and Hydrothermal Rocks Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Metamorphism What happens to rocks that are
More informationMetcalf and Buck. GSA Data Repository
GSA Data Repository 2015035 Metcalf and Buck Figure DR1. Secondary ionization mass-spectrometry U-Pb zircon geochronology plots for data collected on two samples of Wilson Ridge plutonic rocks. Data presented
More informationSupplementary Figure 1 Map of the study area Sample locations and main physiographic features of the study area. Contour interval is 200m (a) and 40m
Supplementary Figure 1 Map of the study area Sample locations and main physiographic features of the study area. Contour interval is 200m (a) and 40m (b). Dashed lines represent the two successive ridge
More informationTHE ORIPÄÄ GRANITE, SW FINLAND: CHARACTERIZATION AND SIGNIFICANCE IN TERMS OF SVECOFENNIAN CRUSTAL EVOLUTION
103 THE ORIPÄÄ GRANITE, SW FINLAND: CHARACTERIZATION AND SIGNIFICANCE IN TERMS OF SVECOFENNIAN CRUSTAL EVOLUTION TAPANI RÄMÖ and MIKKO NIRONEN RÄMÖ, TAPANI and NIRONEN, MIKKO 2001. The Oripää granite,
More informationClassification and Origin of Granites. A Multi-faceted Question
Classification and Origin of Granites A Multi-faceted Question What is a granite? IUGS classification Based on Modal Mineralogy Plutonic rock with less than 90% mafic minerals Alkali Granite Granite Quartz
More informationFluorine and Chlorine in Alkaline Rocks and A-type Granites
Fluorine and Chlorine in Alkaline Rocks and A-type Granites Using the fluorine and chlorine content of Amphibole, Apatite and Biotite to monitor magma halogen content Chilwa Province, Malawi, and Carboniferous
More informationEffect of tectonic setting on chemistry of mantle-derived melts
Effect of tectonic setting on chemistry of mantle-derived melts Lherzolite Basalt Factors controlling magma composition Composition of the source Partial melting process Fractional crystallization Crustal
More informationTowards a new stratigraphy of the Bird River Belt. H.P. Gilbert (MGS)
Towards a new stratigraphy of the Bird River Belt H.P. Gilbert (MGS) Bird River Belt projects initiated in 2005 1. Paul Gilbert (MGS) Regional mapping (1: 20 000 scale) with focus on stratigraphy and geochemistry
More informationof numerous north-south trending Miocene and volcanic centres and lava flows. For
DATA REPOSITORY DR009071 Duggen et al. SAMPLES AND ANALYTICAL METHODS Lavas were collected from a ca. 10 km by 100 km volcanic field consisting of numerous north-south trending Miocene and volcanic centres
More informationLin Chen Robert A Creaser Daniel J Kontak Oct 29th, 2014
FURTHER Re-Os ARSENOPYRITE GEOCHRONOLOGY FROM SELECTED MEGUMA AU DEPOSITS, MEGUMA TERRANE, NOVA SCOTIA: POSSIBLE EVIDENCE FOR A PROTRACTED GOLD-FORMING SYSTEM Lin Chen Robert A Creaser Daniel J Kontak
More informationGEOLOGY AND GEOCHRONOLOGY OF THE ISLAND LAKE GREENSTONE BELT, NORTHWESTERN SUPERIOR PROVINCE by J. Parks 1, S. Lin 1, M.T. Corkery and D.W.
GS-17 GEOLOGY AND GEOCHRONOLOGY OF THE ISLAND LAKE GREENSTONE BELT, NORTHWESTERN SUPERIOR PROVINCE by J. Parks 1, S. Lin 1, M.T. Corkery and D.W. Davis 2 Parks, J., Lin, S., Corkery, M.T. and Davis, D.W.
More informationImagine the first rock and the cycles that it has been through.
A rock is a naturally formed, consolidated material usually composed of grains of one or more minerals The rock cycle shows how one type of rocky material gets transformed into another The Rock Cycle Representation
More informationAPPENDIX 2 Table 2. Sample descriptions
Table 2. descriptions 225 Felsic gneiss, fine-grained and very light-gray. From the upper part of the lower of the two layers, which connect. 226 Amphibolite, even-grained, fine-grained, medium-gray, little
More informationGeology of Quesnel and Stikine terranes and associated porphyry deposits. Jim Logan Paul Schiarizza
Geology of Quesnel and Stikine terranes and associated porphyry deposits Jim Logan Paul Schiarizza Quesnel and Stikine terranes Major cordilleran terranes characterized by similar Late Triassic Early Jurassic
More informationSupplementary material
Supplementary material Supplementary tables Bassis, A., Hinderer, M., Meinhold, G., Petrography and geochemistry of Palaeozoic quartz-rich sandstones from Saudi Arabia: implications for provenance and
More informationA Rock is a solid aggregate of minerals.
Quartz A Rock is a solid aggregate of minerals. Orthoclase Feldspar Plagioclase Feldspar Biotite Four different minerals are obvious in this piece of Granite. The average automobile contains: Minerals
More informationPETROGENESIS OF EARLY SKAGI-SNAEFELLSNES RIFT BASALTS AT GRUNNAVIK, ICELAND
PETROGENESIS OF EARLY SKAGI-SNAEFELLSNES RIFT BASALTS AT GRUNNAVIK, ICELAND SARA JOHNSON Beloit College Sponsor: Jim Rougvie INTRODUCTION The majority of field research in Iceland has been centered on
More informationStudent Name: College: Grade:
Student Name: College: Grade: Physical Geology Laboratory IGNEOUS MINERALS AND ROCKS IDENTIFICATION - INTRODUCTION & PURPOSE: In this lab you will learn to identify igneous rocks in hand samples from their
More informationTrace Elements - Definitions
Trace Elements - Definitions Elements that are not stoichiometric constituents in phases in the system of interest For example, IG/MET systems would have different trace elements than aqueous systems Do
More informationRocks: Materials of the Solid Earth
1 Rocks: Materials of the Solid Earth Presentation modified from: Instructor Resource Center on CD-ROM, Foundations of Earth Science,, 4 th Edition, Lutgens/Tarbuck, Rock Cycle Igneous Rocks Today 2 Rock
More informationPROVENANCE OF A GARNET-RICH BEACH PLACER DEPOSIT, MONTAUK POINT, LONG ISLAND, NY
City University of New York (CUNY) CUNY Academic Works Publications and Research York College Fall 10-23-2006 PROVENANCE OF A GARNET-RICH BEACH PLACER DEPOSIT, MONTAUK POINT, LONG ISLAND, NY Nazrul I.
More informationAppendix 07 Principal components analysis
Appendix 07 Principal components analysis Data Analysis by Eric Grunsky The chemical analyses data were imported into the R (www.r-project.org) statistical processing environment for an evaluation of possible
More information