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Titolo:
Generation and evolution of ore fluids for porphyry Cu-Au mineralization of the Santo Tomas II (Philex) deposit, Philippines
Autore:
Imai, A;
Indirizzi:
Univ Tokyo, Dept Earth & Planetary Sci, Bunkyo Ku, Tokyo 1130033, Japan Univ Tokyo Tokyo Japan 1130033 tary Sci, Bunkyo Ku, Tokyo 1130033, Japan
Titolo Testata:
RESOURCE GEOLOGY
fascicolo: 2, volume: 51, anno: 2001,
pagine: 71 - 96
SICI:
1344-1698(2001)51:2<71:GAEOOF>2.0.ZU;2-4
Fonte:
ISI
Lingua:
ENG
Soggetto:
EL-CHICHON VOLCANO; MOUNT-PINATUBO; SULFUR ISOTOPE; COPPER MINERALIZATION; HYDROTHERMAL SYSTEMS; MINING DISTRICT; MAFIC SILICATES; BAGUIO DISTRICT; 1982 ERUPTIONS; LUZON ARC;
Keywords:
Santo Tomas II (Philex) mine; porphyry Cu-Au deposit; western Luzon arc; Philippines; magmatic water saturation; highly oxidizing condition; silician magnetite; sulfur isotope; hypersaline brine; metallogeny;
Tipo documento:
Review
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
103
Recensione:
Indirizzi per estratti:
Indirizzo: Imai, A Univ Tokyo, Dept Earth & Planetary Sci, Bunkyo Ku, 7-3-1 Hongo, Tokyo 1130033, Japan Univ Tokyo 7-3-1 Hongo Tokyo Japan 1130033 , Tokyo 1130033, Japan
Citazione:
A. Imai, "Generation and evolution of ore fluids for porphyry Cu-Au mineralization of the Santo Tomas II (Philex) deposit, Philippines", RESOUR GEOL, 51(2), 2001, pp. 71-96

Abstract

The Santo Tomas II (Philex) deposit is a porphyry Cu-Au deposit, located in the southern part of the Baguio mineral district, Benguet Province, northern Luzon, Philippines. The Santo Tomas II deposit is associated with an intrusive complex consisting of four rock types that are distinguished based on petrography. They are 1) post-ore clinopyroxene-bearing hornblende andesite porphyry, 2) ore-generating hornblende andesite porphyry, 3) hornblendequartz diorite porphyry and 1) porphyritic hornblende quartz diorite. K-Arage of hydrothermal biotitization was estimated to be 1.5 +/-0.4 Ma. A number of intrusive bodies having broadly similar petrography and K-Ar age occur in the vicinity of the Santo Tomas II deposit, such as at Clifton,Ligay (Binang), Bumolo (Waterhole) and Philex Main Camp areas. The intrusions at the Santo Tomas II deposit and in the vicinity are characterized by high X-Mg (Mg/[Mg+Fe] atomic ratio, about 0.7 or higher) of mafic silicate phenocrysts such as hornblende, and high sulfur contents (> 0.2 wt% as SO3)in accessory microphenocrystic apatite, suggesting a highly oxidizing condition. Sulfur is accommodated dominantly as oxidized species since the crystallization of phenocrysts. Sub-dendritic rim of tremolitic amphibole on homblende phenocryst in the ore-generating andesite porphyry at the Santo Tomas II deposit suggests interaction of magma and aqueous fluid(s) exsolved due to decompression during intrusion. Dissemination of magnetite is associated with hydrothermal biotitization and is followed by sheeted and stockwork quartz veinlets having silician magnetite and rare titanohematite instead of Cu-Fe sulfides. The silician magnetite-rich quartz veinlet was formed at f(O2) near the hematite-magnetite buffer at nearly magmatic temperature, where sulfur dominantly existed as oxidized species such as SO2. Chalcopyrite and bornite, which commonly exhibit micrographic texture often accompanying Pd telluride and native gold/Au-rich electrum, are associated with subsequent anhydrite (-quartz) veinlets and stringers. Both intermediate solid solution (iss) and bornite solid solution (bnss) are thought to have coprecipitated primarily at above 500 degreesC based on fluid inclusion microthermometry and sulfur isotope thermometry applied for anhydrite and associated chalcopyrite and bornite, The initial iss is considered to have converted to chalcopyrite partly replacing bnssduring cooling. The hypersaline polyphase fluid inclusions abundantly found in the sheeted and stockwork quartz as well as anhydrite veinlets with scarce gaseous inclusions suggest that they have been trapped in the two aqueous fluid immiscible region. The western Luzon are associated with porphyry Cu mineralization is characterized by oxidized hydrous magmatism and shallow emplacement, and by the source of sulfur enriched in 335.

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Documento generato il 26/09/17 alle ore 09:11:18