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191.
《International Geology Review》2012,54(15):1835-1864
The Yinshan deposit is a large epithermal-porphyry polymetallic deposit, and the timing and petrogenesis of ore-hosting porphyries have been hotly debated. We present new results from geochemical, whole-rock Sr–Nd and zircon U–Pb–Hf–O isotopic investigations. Zircon U–Pb data demonstrate that the quartz porphyry, dacitic porphyry, and quartz dioritic porphyry formed at ?172.2 ± 0.4 Ma, ?171.7 ± 0.5 Ma, and ?170.9 ± 0.3 Ma, respectively. Inherited zircon cores show significant age spreads from ?730 to ?1390 Ma. Geochemically, they are high-K calc-alkaline or shoshonitic rocks with arc-like trace element patterns. They have similar whole-rock Nd and zircon Hf isotopic compositions, yet an increasing trend in ?Nd(t) and ?Hf(t) values typifies the suite. Older (inherited) zircons of the three porphyries display Hf compositions comparable to those of the Jiangnan Orogen basement rocks. In situ zircon oxygen isotopic analyses reveal that they have similar oxygen isotopic compositions, which are close to those of mantle zircons. Moreover, a decreasing trend of δ18O values is present. We propose that the ore-related porphyries of the Yinshan deposit were emplaced contemporaneously and derived from partial melting of Neoproterozoic arc-derived mafic (or ultra-mafic) rocks. Modelling suggests that the quartz porphyries, dacitic porphyries, and quartz dioritic porphyries experienced ?25%, ?10%, and ?10% crustal contaminations by Shuangqiaoshan rocks. Our study provides important constraints on mantle–crust interaction in the genesis of polymetallic mineralization associated with Mesozoic magmatism in southeastern China. 相似文献
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Jinxiang LI Guangming LI Kezhang QIN Bo XIAO Lei CHEN Junxing ZHAO 《Resource Geology》2012,62(1):19-41
The Early Cretaceous Duolong gold‐rich porphyry copper deposit is a newly discovered deposit with proven 5.38 Mt Cu resources of 0.72% Cu and 41 t gold of 0.23 g t?1 in northern Tibet. Granodiorite porphyry and quartz diorite porphyrite are the main ore‐bearing porphyries. A wide range of hydrothermal alteration associated with these porphyries is divided into potassic, argillic and propylitic zones from the ore‐bearing porphyry center outward and upward. In the hydrothermal alteration zones, secondary albite (91.5–99.7% Ab) occurs along the rim of plagioclase phenocryst and fissures. Secondary K‐feldspar (75.1–96.9% Or) replaces plagioclase phenocryst and matrix or occurs in veinlets. Biotite occurs mainly as matrix and veinlet in addition to phenocryst in the potassic zone. The biotite are Mg‐rich and formed under a highly oxidized condition at temperatures ranging from 400°C to 430°C. All the biotites are absent in F, and have high Cl content (0.19–0.26%), with log (XCl/XOH) values of ?2.74 to ?2.88 and IV (Cl) values of ?3.48 to ?3.35, suggesting a significant role of chloride complexes (CuCl2‐ and AuCl2‐) in transporting and precipitating copper and gold. Chlorites are present in all alteration zones and correspond mainly to pycnochlorite. They have similar Fe/(Fe+Mg), Mn/(Mn+Mg) ratios, and a formation temperature range of 280–360°C. However, the formation temperature of chlorite in the quartz‐gypsum‐carbonate‐chlorite vein is between 190°C and 220°C, indicating that it may have resulted from a later stage of hydrothermal activity. Fe3+/Fe2+ ratios of chlorites have negative correlation with AlIV, suggesting oxygen fugacity of fluids increases with decreasing temperature. Apatite mineral inclusions in the biotite phenocrysts show high SO3 content (0.44–0.82%) and high Cl content (1–1.37%), indicating the host magma had a high oxidation state and was enriched in S and Cl. The highest Cl content of apatite in the propylitic zone may have resulted from pressure decrease, and the lowest Cl content of apatite in the argillic zone may have been caused by a low Cl content in the fluids. The low concentration of SO3 content in the hydrothermal apatite compared to the magmatic one may have resulted from the decrease of oxygen fugacity and S content in the hydrothermal fluid, which are caused by the abundant precipitation of magnetite. 相似文献
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鄂东丰山矿田花岗闪长斑岩体锆石SHRIMP U-Pb定年及其意义 总被引:3,自引:0,他引:3
鄂东丰山矿田是长江中下游多金属成矿带的重要组成部分,由鸡笼山、丰山和李家湾等大-中型铜金多金属矿床组成。矿体产于燕山期花岗闪长斑岩体与三叠系碳酸盐岩接触带中,成矿作用与燕山期花岗闪长斑岩密切相关。作者采用锆石SHRIMP U-Pb定年方法对鸡笼山和丰山矿区成矿斑岩体进行了年代学研究,获得鸡笼山和丰山花岗闪长斑岩的锆石微区原位SHRIMP U-Pb年龄分别为138±2Ma(95%可信度,MSWD=5.1)和137±2Ma(95%可信度,MSWD=1.4),与前人已报道的鄂东南矿集区内典型铜-金-钼-(钨)矿床中辉钼矿Re-Os等时线年龄(140Ma±)吻合,表明丰山矿田成岩成矿事件均发生于早白垩世。本次研究还在鸡笼山花岗闪长斑岩体中发现了新太古代锆石年龄信息,证实了扬子陆块北缘可能存在新太古-古元古代结晶基底。 相似文献
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斑岩铜矿浅部富矿岩浆房研究进展 总被引:6,自引:0,他引:6
在主流的斑岩铜矿模型中,矿床下方都有一个浅部富矿岩浆房,为矿床的最终形成提供成矿流体.国外近年来的大量研究揭示了其基本特征,即位于地表以下约5 km,其大小直接决定着最终矿床的规模,其形态为平卧状,相对封闭,生命周期较短(一般约2 Ma).岛弧或陆缘弧环境有利于浅部富矿岩浆房形成的条件是中等挤压应力状态或挤压后应力松驰... 相似文献
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