NOBLE GASES FINGERPRINT THE SOURCE AND EVOLUTION OF ORE-FORMING FLUIDS OF CARLIN-TYPE GOLD DEPOSITS IN THE GOLDEN TRIANGLE, SOUTH CHINA
NOBLE GASES FINGERPRINT THE SOURCE AND EVOLUTION OF ORE-FORMING FLUIDS OF CARLIN-TYPE GOLD DEPOSITS IN THE GOLDEN TRIANGLE, SOUTH CHINA
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稀有气体指纹识别华南金三角卡林型金矿床成矿流体来源及演化
DOI：
10.5382/econgeo.4703
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发表时间：
2020-03-01
期刊：
影响因子：
5.8
通讯作者：
Li, Jian-Wei
中科院分区：
文献类型：
--
作者：
Jin, Xiao-Ye;Hofstra, Albert H.;Li, Jian-Wei
准确界定金三角地区卡林型金矿成矿流体的来源和演化规律，对于深入认识金矿床成因，建立金成矿的精细成因模式具有重要意义。然而，由于矿床中矿石和脉石矿物的粒度非常细，对矿石流体组分来源的限制长期以来一直是一个挑战。本文通过对水银洞、泥堡、雅塔三个典型金矿主成矿期和成矿晚期的多种矿石和脉石矿物（砷黄铁矿、雄黄、石英、方解石、萤石）流体包裹体提取物的He、Ne、Ar同位素研究，为这一重要金矿省的成矿流体来源和演化提供了新的认识。测得的He同位素的R/RA比值从0.01到0.4不等，这表明地幔中最多有5%的氦，R/RA为8。Ne和Ar同位素组成与空气饱和水大致相当，一些分析表明存在含有核成因38 Ar和放射成因40 Ar的外部流体。绘制的20 Ne/4 He与氦R/RA和3 He/20 Ne与4 He/20 Ne图，结果定义了两个不同的阵列，从一个共同的沉积孔隙流体或深源变质流体端员含有地壳He。成矿期流体主要为含幔源He的岩浆流体和以地壳He为主的沉积孔隙流体或深源变质流体的混合物，成矿晚期流体主要为含地壳He的沉积孔隙流体或深源变质流体和含大气He的浅层大气降水的混合物。结合独立证据，本文的结果支持成矿流体的岩浆成因。成矿期上升岩浆流体与沉积孔隙流体或深源变质流体混合，成矿后期与大气降水混合，形成金三角卡林型金矿。
Precise constraints on the source and evolution of ore-forming fluids of Carlin-type gold deposits in the Golden Triangle (south China) are of critical importance for a better understanding of the ore genesis and a refined genetic model for gold mineralization. However, constraints on the source of ore fluid components have long been a challenge due to the very fine grained nature of the ore and gangue minerals in the deposits. Here we present He, Ne, and Ar isotope data of fluid inclusion extracts from a variety of ore and gangue minerals (arsenian pyrite, realgar, quartz, calcite, and fluorite) representing the main and late ore stages of three well-characterized major gold deposits (Shuiyindong, Nibao, and Yata) to provide significant new insights into the source and evolution of ore-forming fluids of this important gold province. Measured He isotopes have R/RA ratios ranging from 0.01 to 0.4 that suggest a maximum of 5% mantle helium with an R/RA of 8. The Ne and Ar isotope compositions are broadly comparable to air-saturated water, with a few analyses indicating the presence of an external fluid containing nucleogenic 38Ar and radiogenic 40Ar. Plotted on the 20Ne/4He vs. helium R/RA and 3He/20Ne vs. 4He/20Ne diagrams, the results define two distinct arrays that emanate from a common sedimentary pore fluid or deeply sourced metamorphic fluid end-member containing crustal He. The main ore-stage fluids are interpreted as a mixture of magmatic fluid containing mantle He and sedimentary pore fluid or deeply sourced metamorphic fluid with predominantly crustal He, whereas the late ore-stage fluids are a mixture of sedimentary pore fluid or deeply sourced metamorphic fluid bearing crustal He and shallow meteoric groundwater containing atmospheric He. Results presented here, when combined with independent evidence, support a magmatic origin for the ore-forming fluids. The ascending magmatic fluid mixed with sedimentary pore fluid or deeply sourced metamorphic fluid in the ore stage and subsequently mixed with the meteoric groundwater in the late ore stage, eventually producing the Carlin-type gold deposits in the Golden Triangle.