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首页> 外文期刊>Economic geology and the bulletin of the Society of Economic Geologists >Porphyry and Epithermal Deposits and ~(40)Ar/~(39)Ar Geochronology of the Baguio District, Philippines
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Porphyry and Epithermal Deposits and ~(40)Ar/~(39)Ar Geochronology of the Baguio District, Philippines

机译：菲律宾碧瑶地区的斑岩和超热矿床和〜（40）Ar /〜（39）Ar地质年代学

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摘要

The Baguio district is located in the Central Cordillera of northern Luzon, Philippines. It contains numerous mineralized porphyry copper-gold, epithermal gold-silver and skarn gold-lead-zinc deposits. The district is floored by Cretaceous-Eocene metavolcanic and metasedimentary rocks, which are overlain by marine to terrestrial sedimentary and volcanic rocks of early Miocene to Pliocene ages. Tertiary arc magmatism related to east-directed subduction of the South China Sea plate along the Manila Trench beneath northern Luzon produced a major batholith, the Central Cordillera Intrusive Complex, which defines the eastern boundary of the Baguio district. The intrusive complex was emplaced in the early Miocene based on ~(40)Ar/~(39)Ar age determinations for the Lucbuban gabbro (22.6 ± 0.5 Ma) and Virac granodiorite (20.23 ± 0.38 and 20.2 ± 0.7 Ma). Recent exploration has led to the discovery of several new porphyry copper-gold and skarn prospects in the western Baguio district. Mineralization was preceded by the intrusion of a suite of hornblende megacrystic andesite dikes in the central part of the district from 4.55 ± 0.15 to 3.45 ± 0.19 Ma. Porphyry copper-gold and skarn deposits at Black Mountain and Mexico, on the western side of the district, formed between 3.09 ± 0.15 and 2.81 ± 0.24 Ma. The Santo Tomas II Cu-Au-(Pd) porphyry deposit was emplaced into the central southern part of the district at about 1.5 Ma, based on secondary biotite ~(40)Ar/~(39)Ar ages of 1.48 ± 0.05 Ma and 1.47 ± 0.05 Ma. On the eastern side of the district, porphyry-style mineralization at the Hartwell and Ampucao porphyry Cu-Au prospects returned ~(40)Ar/~(39)Ar ages of 1.09 ± 0.10 and 0.51 ± 0.26 Ma, respectively. Quartz-carbonate-base metal sulfide style epithermal gold-silver veins are well-developed on the eastern side of the Baguio district, and crosscut porphyry-style mineralization at the Acupan, Baguio gold and Nugget Hill deposits. Epithermal veining is inferred to have occurred in the past million years, based on a reported K-Ar age determination of 0.65 ± 0.07 Ma from the Acupan gold mine. A large advanced argillic alteration zone (the Baguio lithocap) crops out in the northwest part of the district, and formed between 1.4 and 0.9 Ma, based on previous K-Ar dating. Pliocene-Pleistocene mineralization in the Baguio district was triggered by the east-directed subduction of the Scarborough Ridge. Ridge subduction caused the subduction angle along the Manila Trench beneath northern Luzon to decrease, which facilitated crustal thickening and exhumation. Ridge subduction also promoted the development of northwest-trending faults in the upper plate that interacted with major arc-parallel north- and arc-normal northeast-trending fault sets associated with the Philippine fault system. Fertile magmas were emplaced into transtensional strike-slip relay basins, resulting in the accumulation of more than 35 Moz of gold and several million tonnes of copper over approximately 3 m.y.
机译：碧瑶区位于菲律宾北部吕宋岛的中央山脉。它包含大量矿化斑岩铜金，超热金银和矽卡岩金铅锌矿床。该地区以白垩纪-始新世的准火山岩和准沉积岩为基底，它们被中新世至上新世时代的海相至陆相沉积和火山岩所覆盖。与沿吕宋岛北部的马尼拉海沟南中国海板块向东俯冲有关的第三弧岩浆作用产生了一个主要的岩基，即中央山脉侵入复合体，它定义了碧瑶地区的东部边界。根据〜（40）Ar /〜（39）Ar年龄测定的Lucbuban gabbro（22.6±0.5 Ma）和Virac granodiorite（20.23±0.38和20.2±0.7 Ma），将侵入体置于中新世早期。最近的勘探导致在碧瑶西部地区发现了一些新的斑岩型铜金和矽卡岩矿。在矿化之前，在该区域的中部侵入了一组角闪闪的大型结晶安山岩堤防，范围从4.55±0.15到3.45±0.19 Ma。该地区西侧的黑山和墨西哥的斑岩铜金和矽卡岩矿床形成在3.09±0.15和2.81±0.24 Ma之间。基于次生黑云母〜（40）Ar /〜（39）Ar年龄为1.48±0.05 Ma和1.47±0.05毫安。在该区的东部，Hartwell和Ampucao斑岩Cu-Au前景的斑岩型矿化分别使〜（40）Ar /〜（39）Ar年龄分别为1.09±0.10和0.51±0.26 Ma。碧瑶地区东部发育着以碳酸盐为基础的金属硫化物样式的超热金银矿脉，并且在Acupan，碧瑶金矿和金块山矿床形成了斑岩斑岩型矿化。根据报告的Acupan金矿的K-Ar年龄确定为0.65±0.07 Ma，推断在过去一百万年中发生了超热脉动。根据先前的K-Ar年代测定，该地区的西北部出现了一个大型的晚期泥质蚀变带（碧瑶岩帽），形成在1.4至0.9 Ma之间。碧瑶地区的上新世至更新世矿化是由斯卡伯勒岭向东俯冲所触发的。脊俯冲使吕宋岛北部的马尼拉海沟沿俯冲角减小，这有利于地壳增厚和发掘。脊俯冲也促进了上板块西北向断裂的发展，该断裂与与菲律宾断裂系统相关的主要弧平行的北向和弧线正常的东北向断裂集相互作用。肥沃的岩浆被放入了张性走滑中转盆地，导致在约3 m。y上积聚了35莫兹的黄金和几百万吨的铜。

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