Sample photos and petrographic descriptions of core samples from the Norwegian continental margin basement

Size: px

Start display at page:

Download "Sample photos and petrographic descriptions of core samples from the Norwegian continental margin basement"

Job Hunter
6 years ago
Views:

1 Sample photos and petrographic descriptions of core samples from the Norwegian continental margin basement Appendix 1 Petrophysical and thermal properties of pre-devonian basement rocks on the Norwegian continental margin Trond Slagstad, Cécile Barrére, Børre Davidsen, Randi K. Ramstad

2 16/1-4, 1937m Utsira High, North Sea Medium- to coarse-grained, undeformed gabbro consisting of roughly equal amounts of amphibole+biotite and strongly saussuritised plagioclase. The amphibole is typically partly altered to biotite. Small, calcite-filled veins and vugs are common

3 16/3-2, m North Sea Medium-grained, red granite consisting of fine-grained, whitish-red to red feldspar and coarser (<1 cm) irregular, but generally rounded, grains of quartz. The granite is unfoliated and spotted with 1 2 mm specks of biotite and muscovite, homogeneously distributed in the rock.

16/4-1, 2907.4m Utsira High, North Sea Compositely layered, fine-grained, light grey impure quartzite and dark grey siltstone. Layer thickness varies from ca. 1 mm up to several cm.

4 16/4-1, m Utsira High, North Sea Compositely layered, fine-grained, light grey impure quartzite and dark grey siltstone. Layer thickness varies from ca. 1 mm up to several cm. The quartz-rich layers are rich in epidote, whereas biotite and feldspar dominate in the 'silty' layers. The mineral assemblage indicates low-grade metamorphism. The sample is criss-crossed by thin, calcite-filled vein, dominantly subvertical although subhorizontal veins are also found. The subvertical veins appear to form en echelon patterns, and some of the veins are only developed in the quartzite but are not visible in the siltstone. This effect is most likely caused by differences in rheology of the two rock types. Some cm-thick, green to orange layers, slightly oblique to the layering in the rock appear to consist of epidote and albite (?) and are most likely metasomatic.

16/4-1, 2908.6m Utsira High, North Sea Fine-grained granite, grey with a reddish hue.

5 16/4-1, m Utsira High, North Sea Fine-grained granite, grey with a reddish hue. The granite is unfoliated with 1 3 mm specks of biotite and minor muscovite, homogeneously distributed in the rock.

6 16/5-1, m Utsira High, North Sea Fine-grained, unfoliated, dark red granite with scattered 1 3 mm specks of biotite and muscovite, homogeneously distributed in the rock. There are some cracks in the sample with discontinuous, thin, bleached margins, indicating some alteration.

7 16/6-1, m Utsira High, North Sea Fine-grained, undeformed, grey volcanic rock with abundant small (<2 mm) phenocrysts of plagioclase in a fine-grained, feldspar+chlorite+quartz groundmass. The rock also contains a small (ca. 4 cm) inclusion of slightly coarser grey rock, probably a xenolith.

17/3-1, 2849.5m Stord Basin, North Sea Dark green fault breccia with abundant calcite-filled veins and vugs.

8 17/3-1, m Stord Basin, North Sea Dark green fault breccia with abundant calcite-filled veins and vugs. The fine-grained matrix consists mainly of chlorite. From NPD's Fact-page: " drilled [ ] in metamorphic basement rock, dated 410 My".

9 17/3-1, m Stord Basin, North Sea Fault breccia consisting predominantly of medium-grained, strongly undulatory quartz and calcite, typically forming irregular veins in a fine-grained quartz+feldspar matrix with some chlorite.

10 18/11-1, m Stavanger Platform, North Sea Dark green, volcanic rock with plagioclase phenocrysts, typically 1 2 mm across with a prismatic, rounded to angular shape, set in a fine-grained, quartz+feldspar matrix. The rock is criss-crossed by numerous, white, hairline veins that locally are calcitefilled.

25/7-1S, 3548.2m North Sea Breccia with irregular fragments typically ca.

11 25/7-1S, m North Sea Breccia with irregular fragments typically ca. 5 cm long of a dark red, fine-grained rock, consisting mainly of opaque minerals and calcite. The fragments have slightly rounded edges.

25/7-1S, 3554.3m North Sea Faintly banded, fine-grained, grey metasandstone.

12 25/7-1S, m North Sea Faintly banded, fine-grained, grey metasandstone. The metasandstone consists mainly of undulatory quartz, with lesser amounts of altered feldspar (mainly K- feldspar), and prismatic muscovite oriented parallel to the foliation in the rock. The faint banding represents variation in the proportions of these minerals. Chlorite is an accessory phase. The metasandstone is criss-crossed by numerous thin veins, with dark green, white or brown, calcareous infilling.

13 25/11-17, m Balder/Grane area, North Sea Microcrystalline to fine-grained, dark brown to grey metasiltstone consisting mainly of quartz, feldspar and biotite, with minor muscovite and calcite. The rocks are crisscrossed by numerous short (<2 cm), irregular veins and vugs filled with white calcite and red zeolite.

35/3-4, 4088.3m North Sea Fine-grained, dark grey biotite gneiss.

14 35/3-4, m North Sea Fine-grained, dark grey biotite gneiss. The biotite gneiss consists mainly of quartz, K-feldspar and plagioclase, with rather abundant biotite forming a well-defined foliation in the rock. Epidote constitutes several percent of the rock, and is typically enriched in the more biotite-rich layers. Concordant, mm-sized patches and veins of medium-grained quartz are common. The rock contains a fair amount of pyrite, some with well-developed crystal faces, typically 1 2 mm across but locally up to 5 mm.

15 35/9-1, m North Sea Fine-grained, dark green breccia consisting of fine-grained chlorite and calcite. Colour varies from light grey, green, dark green to dark grey, giving the rock a speckled appearance. The breccia contains some mm-thick, calcite-filled veins. No larger clasts can be observed.

16 36/1-1, m North Sea Fine-grained, grey, biotite-epidote-bearing granitic gneiss. Abundant biotite laths impart the gneiss with a strong foliation. Note that the indicated sample depth in the photo label is in feet, not metres.

6305/12-2, 3158.3m Norwegian Sea Grey fault(?

17 6305/12-2, m Norwegian Sea Grey fault(?) breccia consisting dominantly of angular fragments of a fine-grained chlorite+feldspar+calcite rock, separated by thin calcite veins. Numerous calcitefilled veins and vugs..

18 6306/10-1, m Frøya High, Norwegian Sea Medium-grained, unfoliated quartz diorite consisting of sassuritised plagioclase, hornblende that is commonly partly or completely altered to chlorite, and minor quartz and epidote. A few calcite-filled cracks are present.

19 6306/10-1, m Frøya High, Norwegian Sea Medium-grained, unfoliated quartz diorite consisting of sassuritised plagioclase, hornblende that is commonly partly or completely altered to chlorite, some quartz and minor epidote. A few calcite-filled cracks are present.

20 6407/10-3, m Norwegian Sea Medium-grained, unfoliated, dark red granite with small specks (<1 mm) of biotite.

21 6609/7-1, m Norwegian Sea Breccia with angular, mm- to cm-size fragments of fine-grained, reddish grey, quartzrich metasandstone. The metasandstone contains several percent elongate muscovite which forms the foliation in the rock, and minor amounts of calcite. The matrix between the fragments consists of crumbly, microcrystalline, green material, and minor amounts of red to brown calcareous material.

22 6609/7-1, m Norwegian Sea Laminated metasiltstone consisting of layers, typically < 1 cm thick, of fine-grained, quartz-rich metasiltstone with a orange hue, and thinner layers of grey, muscovite-rich metasiltstone. The rock is extensively cracked with calcite-filled veins.

23 7120/1-1, m Loppa High, Barents Sea Fine-grained, foliated, amphibolite, consisting mainly of amphibole and calcite, with minor titanite.

24 7120/2-1, m Loppa High, Barents Sea Diabase.

25 7120/2-1, m Loppa High, Barents Sea Diabase.

26 7120/12-2, m Norwegian Sea Dark grey mylonititc, granitic augen gneiss, with numerous thin (<1 mm) and some thicker (<1 cm) leucocratic veins, concordant with the foliation in the rock.

7120/12-2, 4678.2m Norwegian Sea Dark grey mylonitic, granitic augen gneiss, with numerous thin (<1 mm) and some thicker (<1 cm) leucocratic veins, concordant with the foliation in the rock.

27 7120/12-2, m Norwegian Sea Dark grey mylonitic, granitic augen gneiss, with numerous thin (<1 mm) and some thicker (<1 cm) leucocratic veins, concordant with the foliation in the rock. Dispersed, oriented biotite and minor muscovite, along with stretched quartz and feldspar, constitute the foliation. It is conceivable that some of the leucocratic bands represent stretched out K-feldspar phenocrysts.

7128/4-1, 2527.0m Finnmark Øst area, Barents Sea Laminated shaly siltstone, with upward-fining layers of fine-grained sandstone (at base) through siltstone to shale (at top).

28 7128/4-1, m Finnmark Øst area, Barents Sea Laminated shaly siltstone, with upward-fining layers of fine-grained sandstone (at base) through siltstone to shale (at top). Some layers display erosional bases. Although many primary sedimentary features are preserved in the rock, chlorite with poorly-developed tails in the fine-grained layers suggest low-grade metamorphism and a certain degree of deformation. The appearance of this rock is similar to sandstones and shales of turbiditic origin in the Kongsfjord Fm. or lower part of the overlying Båsnæringen Formation on the Varanger Peninsula (A. Siedlecka, pers. com., 2006). References (Siedlecka 1972, Siedlecka and Edwards 1980, Pickering 1981, Siedlecka et al. 1995)

7128/4-1, 2527.2m Finnmark Øst area, Barents Sea Finely laminated siltstone, alternating with mm-thick upward-fining layers of sandy siltstone.

29 7128/4-1, m Finnmark Øst area, Barents Sea Finely laminated siltstone, alternating with mm-thick upward-fining layers of sandy siltstone. Locally the sandstone layers appear to have erosional bases, indicated by what appears to be scour marks filled with relatively coarse sandstone. The appearance of this rock is similar to sandstones and shales of turbiditic origin in the Kongsfjord Fm. or lower part of the overlying Båsnæringen Formation on the Varanger Peninsula (A. Siedlecka, pers. com., 2006). References: (Siedlecka 1972, Siedlecka and Edwards 1980, Pickering 1981, Siedlecka et al. 1995)

30 7128/4-1, m Finnmark East area, Barents Sea Laminated fine-grained sandstone and shale, quite similar to 7128/4-1, m, but without the apparent sedimentary features. The appearance of this rock is similar to sandstones and shales of turbiditic origin in the Kongsfjord Fm. or lower part of the overlying Båsnæringen Formation on the Varanger Peninsula (A. Siedlecka, pers. com., 2006). References: (Siedlecka 1972, Siedlecka and Edwards 1980, Pickering 1981, Siedlecka et al. 1995)

7128/6-1, 2540.5m Finnmark Øst area, Finnmark Platform, Barents Sea Fine-grained, layered metasandstone, with alternating layers of rusty brown sandstone (0.5 1.5 cm thick) and grey sandstone (0.

31 7128/6-1, m Finnmark Øst area, Finnmark Platform, Barents Sea Fine-grained, layered metasandstone, with alternating layers of rusty brown sandstone ( cm thick) and grey sandstone (0.5 1 cm thick). The sandstone is homogeneous and consists of ca. 0.5 mm poorly rounded quartz and feldspar grains in a calcite-dominated matrix. The poor rounding and rather large amount of feldspar indicate that the sediment was relatively immature. Røe and Roberts (1992) described the sandstone in detail, and argued for lowermost greenschist-facies metamorphism and postdepositional deformation.

32 7128/6-1, m Finnmark Øst area, Finnmark Platform, Barents Sea Fine- to medium-grained, layered metasandstone, with alternating layers of rusty brown sandstone ( cm thick) and grey sandstone (0.5 1 cm thick).

33 7226/11-1, m Norsel High, Bjarmeland Platform, Barents Sea Strongly foliated, medium-grained, biotite-rich schist (amphibolite?) with pods and layers of quartz.

7226/11-1, 5198.8m Norsel High, Bjarmeland Platform, Barents Sea Strongly foliated, medium-grained, biotite-rich schist with pods and layers of quartz.

34 7226/11-1, m Norsel High, Bjarmeland Platform, Barents Sea Strongly foliated, medium-grained, biotite-rich schist with pods and layers of quartz. In addition to biotite, the matrix contains quartz, feldspar and some clinozoisite. The rock also contains sulphides, most likely pyrite, aligned with the foliation.

35 References Pickering, K.T. (1981) The Kongsfjord Formation - a Late Precambrian submarine fan in north-east Finnmark, North Norway. Norges geologiske undersøkelse, 367, Røe, S.-L. and Roberts, D. (1992) Basement-core sandstones in well 7128/6-1, southern Barents Sea, and correlation with onshore, Upper Proterozoic sequences of northeastern Finnmark. Geological Institute, University of Bergen, Unpublished report, 33 pp. Siedlecka, A. (1972) Kongsfjord Formation-a Late Precambrian Flysch Sequence form the Varanger Peninsula, Finnmark. Norges geologiske undersøkelse, 278, Siedlecka, A. and Edwards, M.B. (1980) Lithostratigraphy and sedimentation of the Riphean Båsnæringen Formation, Varanger Peninsula, North Norway. Norges geologiske undersøkelse, 355, Siedlecka, A., Negrutsa, V.Z. and Pickering, K.T. (1995) Upper Proterozoic Turbidite System of the Rybachi Peninsula, northern Russia - a possible stratigraphic counterpart of the Kongsfjord Submarine Fan of the Varanger Peninsula, northern Norway. Norges geologiske undersøkelse Special Publication, 7,

Introduction to Geology Spring 2008

MIT OpenCourseWare http://ocw.mit.edu 12.001 Introduction to Geology Spring 2008 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms. Regional metamorphism