Maalinao-Caigutan-Biyog (MCB), a very young porphyry - high sulfidation epithermal Cu-Au deposit in the northern Luzon Central Cordillera, Philippines Introduction The MCB Project at Batong Buhay, Kalinga, Philippines is operated by Makilala Mining Company, Inc. Leonardo L. Subang 09 June, 2011 A core drilling program started in December 2006. A total of 38 holes had been completed, with an aggregate drill length of 19,517m as of March, 2011. The Batong Buhay area is located about 320 aerial km north of Manila, in Barangay Balatoc, Municipality i of Pasil, Kalinga Province. Location and access 19º 18º 17º 120º 121º The Project is covered by Exploration Permit No. 003A- 2006 (granted January, 2006) with a total area of 2,700 hectares. The EP surrounds the Batong Buhay Gold Mines Inc. tenement which covers the ground occupied by the Dickson Porphyry Cu-Au deposit. EP-003A-2006- Tuguegarao CAR Tabuk Lubuagan 122º Tectonic setting It is most conveniently 16º reached from Manila thru the Tuguegarao 15º Tabuk -Lubuagan route. Baguio Manila The subduction of the Scarborough Ridge has played an important role in causing the Cu-Au deposition and high uplifterosion rates in northern Luzon (Cooke et al., 2005). District geology The Kalinga Mineral District is underlain by a basement of Paleogene basaltic lavas and volcaniclastics. The old volcanic rocks are overlain by Oligocene- Miocene sediments consisting of interbedded sandstone, conglomerate and limestone. The basalts and marine sediments were intruded by several phases of volcanism that started from Early Miocene and continued up to the present. Volcanic setting of FMI prospects Botilao Cu-Au Prospect Tabia Cu-Au Prospect MCB Cu-Au Project MCB, Botilao and Tabia Cu-Au prospects are situated on an eroded volcano complex. Volcanic center migrating eastwards.
Deposit geology MCB Cu-Au deposit is a partially telescoped porphyryepithermal system. It is a product of multiple mineralization events in the Pliestocene, characterized by the superimposition of HS-IS epithermal mineralization on 3 phases of porphyry mineralization. The geological features of the deposit exhibit magmatic as well as hydrothermal evolution. The MCB intrusive complex consists of 3 porphyry Cu ore-forming tonalitic intrusion phases, namely: early dark tonalite (DT-1), light tonalite (LT) and late dark tonalite (DT-2) These are distinguished on the basis of phenocryst composition and texture and associated alteration, veining & mineralization. Deposit geology Maalinao- Mt. Mines Caigutan Biyog Dickson Biyog Amfertungan Binasalan Recent dacite pyroclastics Recent dacite pyroclastics Maalinao-Mt. Mines Caigutan Biyog HBxa Quartz + alunite ± pyrophyllite altered hydrobrecciated basalt Quartz + alunite ± pyrophyllite altered hydrobrecciated basalt Biyog Hbx: 1.2km long and 300m at its widest cross section. Contains abundant porphyry stockworked clasts. Early Porphyry Cu-Au (P1) Amfertungan steaming ground Hosted in dark tonalite and intruded basalt. Early quartz+magnetite+cu-sulfide veinlets in Na- Ca (albite+tremolite+actinolite) and potassic (biotite) alteration and later quartz+cusulfide+magnetite /hematite veinlets in intermediate argillic (chlorite-sericite) alteration. Cu-sulfide assemblages bornite-rich in Na-Ca alteration and chalcopyrite-rich in K & IA alteration. Cu mineralization associated with high Au, low Mo signature.
DT-1 MCB-18 477.70m: Bi-Epi-Chl Alteration in DT-1 Basalt MCB-002 281m: Act-Bi Alteration in Basalt MCB-09 510.50m: Bi-Chl-Se Alteration in DT-1 MCB-002 201m: Bi-Chl-Se Alteration in Basalt Basalt MCB-09 497.50m: Se Alteration in Basalt MCB-09 436.40m: Se Alteration in Basalt Intermediate porphyry Cu±Au±Mo (P2) Hosted in light tonalite and intruded DT-1 and basalt. Characterized by abundant anhydrite accompanying quartz veinlets in chlorite+sericite (intermediate argillic) alteration. Overprinted itdby much hthik thicker anhydrite hdit veinlets ilt in quartz+sericite t+ iit (phyllic) alteration. Cu-sulfides a mix of chalcopyrite and bornite in both intermediate argillic and phyllic phases. Molybdenite and sphalerite occasionally present in both alteration phases. Cu mineralization associated with low Au and erratic elevated Mo and Zn signature. LT MCB-03 443m: Bi-Chl-Epi Alteration in LT LT MCB-08 225m: Bi-Se Alteration in LT Pasil R. Outcrop: Ch-Se Alteration in LT MCB-03 267.25m: Bi-Se Alteration in LT
LT MCB-10A 276.80m: Bi-Chl-Epi Alteration in LT MCB-10A 174.50m: Si-Se Alteration in LT Late Porphyry Cu-Au (P3) Hosted in late dark tonalite (DT-2) and intruded basalt. Early quartz/anhydrite+magnetite+cu-sulfide veinlets in potassic (biotite) alteration. Followed by quartz/anhydrite+cu-sulfide+magnetite /hematite veinlets in intermediate argillic (chloritesericite) alteration. Late anhydrite+cu-sulfide+pyrite veinlets in phyllic (sericite) alteration. Cu-sulfide assemblages chalcopyrite-rich in K & IA, and phyllic alteration. Cu mineralization associated with high Au, low Mo signature. DT-2 DT-2 IBx MCB-20 157m: Bi-Epi-Chl Alteration in DT-2 MCB-20 123.75m: Bi-Epi-Chl Alteration in DT-2 IBx MCB-07 147.25m: Chl-Se Alteration in DT-2 MCB-11 261.40m: Chl-Se Alteration in DT-2 IBx HS epithermal Cu±Mo±Au Mineralization fed along sub-vertical shears and hydrothermal breccias at the margins of intrusive complex. Early mineralization of pyrite+bornite+covellite in quartz+muscovite/illite±pyrophyllite alteration in overprinted stockworked porphyries and light tonalite generated intrusive hydrothermal breccias. Late mineralization of enargite+luzonite in chalcedonic quartz+anhydrite±barite veins and opallized hydrothermal breccias with alunite+illite+kaolinite±diaspore floodings. Molybdenite occurs in both mineralization phases, but is much stronger in the later phase. DT-1 MCB-02 139.20m: Qtz-illite Alteration in DT-1 MCB-03 110.30m: Qtz-illite Alteration in DT-1
LT-2 MCB-02 532.20m: Qtz-illite Alteration in LT Basalt MCB-21 71.60m: Qtz-illite-Alu Alteration in Basalt MCB-02 357.30m: Qtz-illite Alteration in LT MCB-23 134.90m: Qtz-illite-Alu Alteration in Basalt P1 & P3 Ore Mineral Assemblages Cp+Bn+Mt/Hm > Cp+Py Chalcedony +Lz/En/Cv Veins MCB-01 187.50m: Anh+Py+En/Lz Vn CBG-01 273.70m: Qtz/Chal+Alu+Cv P2 Ore Mineral Assemblages Cp+Py+Sp > Cp+Bn+Mt > Mo+Py+Sp HS-1 Ore Mineral Assemblages: Py+Bn+Cv/Cc+Cp+Sp > Cp+Bn+Py+Sp
U-Pb in zircon LA-ICPMS geochronology Zircon is a common accessory mineral in intermediate to felsic igneous rocks and contains 10 2-10 3 ppm U. The closure temperature for Pb retention in zircon is above 900ºC (Lee et al., 1997). This closure temperature is within the range of crystallization temperatures of intermediate magmas. U-Pb dating of zircon can, therefore, provide close approximations of intrusion crystallization age. U-Pb ages are less susceptible to resetting by later thermal events compared to other geochronometers such as Ar-Ar in biotite (Harrison and Zeitler, 2005). Although less accurate compared to using Sensitive High Resolution Ion Microprobe (SHRIMP) to analyze U and Pb isotopes, LA-ICPMS is relatively much cheaper and has faster turn-around time of results, making it a more practical dating method to apply in mineral exploration. Pleistocene ages (1.08 ± 0.9Ma to 0.28 ± 0.15Ma) for ore-forming porphyries - ~0.80My Cu-Au fertile magmatism. Mean ages of porphyries: 0.67 ± 44Ma for DT-1; 0.50 ± 0.22Ma for LT; and 0.29 ± 0.22Ma for DT-2. U-Pb LA-ICPMS dating results Late Eocene to Early Oligocene ages (37.4 ± 1.9Ma to 32.5 ± 1.1Ma) with mean age of 34.6 ± 1.8Ma, placing the time of the Kalinga batholith crystallization at Early Oligocene U-Pb LA-ICPMS dating results Conclusion - 1 The 3 phases of MCB porphyry Cu-Au deposition were formed in the Late Pleistocene over a period of about 0.80My. So far, MCB is the youngest Philippine porphyry deposit systematically age dated. 2.5 2 1.5 1 0.5 0 MCB5-600 mcb-19-82 MCB-22-222 mcb-8-262 MCB18-301 MCB18-509 MCB3-441 mcb-18-550 MCB8-110 mcb-8-226 mcb-19-385 MCB20-469 Conclusion - 2 Underplating hot mafic melts were cyclically injected into the upper chambers of colder felsic magma at the beginning and end of ~0.80My period, causing hybrid tonalite porphyries to crystallize. Model of geological setting proposed by Hattori and Keith (2001) for porphyry Cu. Conclusion - 3 The porphyries were shallowly emplaced at about a kilometer below the Batong Buhay volcanic edifice, generating Au-rich porphyry Cu mineralization. Cu and Au are dominantly transported in a buoyant S-rich vapor, co-existing with minor brine in a 2-phase magmatic hydrothermal system. At a depth of <3km, the solubility of both Cu and Au decreases rapidly with decreasing density of the ascending vapor plume, forcing both metals to be coprecipitated. In contrast, magmatic vapor cooling at a depth of >3km under greater confining pressure is likely to precipitate Cu ± Mo, while the S-complexed Au remains dissolved in the relatively dense vapor (Williams-Jones Fluid inclusions of shallow Au-rich porphyry Cu et al., 2002; Redmond et al., 2004) deposits (a & b) from Bajo dela Alumbrera, Argentina and deep high pressure Au-poor porphyry Cu deposits (b & C) from Butte, Montana (Murakami et al., 2009 ).
Exploration implications and challenges Au-rich porphyry Cu deposits are more likely to be found in young arcs than in old deeply eroded arcs. Arc segments with high uplift and erosion rates are more likely to expose shallowly emplaced porphyries. Deposits in young arcs may still be partly to completely covered by young volcanics and sediments. Deposits in young arcs may be situated in an area with a still active geothermal system.