湘东锡田印支期与燕山期花岗岩特性对比及对成矿潜力差异的控制
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1.中国地质科学院郑州矿产综合利用研究所;2.中国地质调查局武汉地质调查中心

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中国地质调查局花岗岩中心成岩成矿研究中心开放基金课题(编号PM202310)、国家自然科学基金项目(编号U2344206)和中国地质调查项目(编号DD20230038)


A comparison of the characteristics of Indosinian and Yanshanian granites and their control on the different W-Sn mineralization potential in Xitian Region, Eastern Hunan Province
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1.Zhengzhou Institute of Multipurpose Utilization of Mineral Resource, Chinese Academy of Geologecal Sciences;2.Wuhan Center of Geological Survey, China Geological Survey

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    摘要:

    湘东锡田发育多期次岩浆活动与钨锡成矿作用,其中印支期花岗岩成矿作用较弱,燕山期花岗岩成矿作用强烈,但导致两期花岗岩成矿强弱差异的因素尚不清楚。本文选取该区印支期和燕山期花岗岩作为研究对象,开展锆石U-Pb年代学、锆石Lu-Hf同位素、岩石地球化学及矿物成分对比研究。结果表明,两期花岗岩锆石LA-ICP-MS U-Pb年龄分别为240.0±1.3Ma和152.9±1.0Ma,分别属于印支期和燕山期。两期花岗岩均具有富铝,贫镁,Rb、K、U、Th相对富集,Ti、P、Sr、Ba、Nb相对亏损的特征。印支期和燕山期花岗岩的锆石εHf(t)值均集中分布于-7.0~-5.0,熔融温度均大于750℃,锆石TDM2值分别集中于1.65~1.70Ga和1.55~1.60Ga,暗示均为古元古代古老地壳高温部分熔融产物,但燕山期花岗岩的源岩更年轻。印支期和燕山期花岗岩的全岩Zr/Hf比值分别为26.1~36.3和7.0~22.7,Nb/Ta比值分别为3.9~7.6和1.2~3.9,暗示均经历了高分异演化过程;锆石氧逸度?FMQ值分别为-0.42~2.61、-2.33~-0.08,黑云母Ⅳ(F)值分别为1.15~1.26、0.71~0.87,暗示燕山期花岗岩具有更低的氧逸度和更高的F富集程度。因此,更加富集的岩浆源区、更低的岩浆氧逸度和更加富集F元素是燕山期花岗岩较印支期具有更大钨锡成矿潜力的重要原因。

    Abstract:

    There are multiperiodic magmation and W-Sn mineralization in Xitian region, Eastern Hunan province, The Indosinian granite mineralization was relatively weak, while the Yanshanian granite mineralization was pronounced. The critical factors controlling the difference in the potential of W-Sn mineralization between the two periods of granite are still unclear. In this paper, we report Zircon U-Pb chronology, Zircon Lu-Hf isotope data, whole rock geochemistry and mineral composition for Indosinian and Yanshanian granites in Xitian region. The zircon LA-ICP-MS U-Pb dating yielded magmatic crystallization ages of 240.0±1.3Ma and 152.9±1.0Ma, corresponding to the Indosinian and Yanshanian periods, respectively. Both periods of granite are characterized by high Al2O3 contents, low MgO contents, enriched in Rb, K, U, Th and depleted in Ti, P, Sr, Ba, Nb. The Zircon εHf(t) values (concentrated between -7.0 and -5.0) and melting temperature(>750℃) of the two periods of granite are similar, The Zircon TDM2 values of Indosinian granite and Yanshanian granite are concentrated at 1.65-1.70Ga, 1.55-1.60Ga, suggesting a magmatic source which was partial melting of ancient crust of the Paleoproterozoic era at high temperature, but the source rocks of the Yanshanian granites are younger than Indosinian granites. The whole-rock Zr/Hf ratios of Indosinian and Yanshanian granite are 26.1-36.3 and 7.0-22.7, and the Nb/Ta ratios are 3.9-7.6 and 1.2-3.9, suggesting that both of them have experienced high differentiation evolution. The magma oxygen fugacity of the Indosinian granite (ΔFMQ=-0.42~2.61) is higher than that of the Yanshanian granite (ΔFMQ=-2.33~-0.08). The Ⅳ(F) of biotite indicates that Indosinian granites have lower concentration of F (Ⅳ(F)=1.15~1.26) than Yanshanian granites (Ⅳ(F)=0.71~0.87). Consequently, more enriched magmatic source region, lower oxygen fugacity and higher F abundance may be the main reasons why Yanshanian granites have more pronounced mineralization than Indosinian granites.

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  • 收稿日期:2024-06-14
  • 最后修改日期:2024-08-01
  • 录用日期:2024-09-06
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