Volatile budgets and gold mobilization in metasomatized sub-continental lithospheric mantle

IF 4.5 1区 地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS Geochimica et Cosmochimica Acta Pub Date : 2024-05-23 DOI:10.1016/j.gca.2024.05.022
Yanning Wang , Qingfei Wang , David I. Groves , Shengchao Xue , Tingyi Wang , Lin Yang , Jun Deng
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Abstract

Metasomatized sub-continental lithospheric mantle (SCLM) is increasingly proposed to control the formation of giant hydrothermal gold provinces. However, the key budgets for gold and volatile components in the SCLM under gold provinces remain poorly constrained, thus hindering definitive genetic models of gold metallogenesis. The Cenozoic hydrothermal orogenic gold deposits in the Ailaoshan gold belt in SE Tibet that are genetically related to metasomatized SCLM, and adjacent penecontemporaneous lamprophyre dikes that are suggested to have a similar source, provide a rare opportunity to resolve this source budget issue. Integrated data on siderophile elements of the lamprophyre dikes, volatile contents of their melt inclusions, and their whole-rock geochemistry are utilized to constrain the source they share with the gold deposits. The lamprophyre primary magmas are characterized by high H2O (3.6 wt%), Cl (up to ∼4700 ppm) and S (up to ∼3100 ppm) concentrations, with modeling suggesting that their mantle sources are also significantly enriched in volatiles (H2O > 1000 ppm, Cl > 60 ppm), overlapping with those of the most volatile-rich magmas and mantle endmembers in the earth. Excluding those dikes that were either affected by auriferous fluids or experienced sulfide separation, the dikes have variable but generally normal Au concentrations (0.10–3.33 ppb), with estimated mantle sources comprising less than 1 ppb Au. This range is lower than or comparable to that of Au contents of global mantle peridotites and the primitive upper mantle, indicating that metasomatism processes did not significantly fertilize the SCLM beneath the gold province with anomalously high Au. Consequently, it appears that high volatile contents of the metasomatized SCLM, which promoted generation of auriferous fluid, ore-metal extraction, subsequent fluid transfer and advection, had a more important, and previously underestimated role in formation of the gold deposits.

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变质次大陆岩石圈地幔中的挥发性预算和金动员
人们越来越多地提出,变质的次大陆岩石圈地幔(SCLM)控制着巨型热液金矿带的形成。然而,金矿带下的SCLM中金和挥发性成分的关键预算仍未得到很好的确定,从而阻碍了金矿成矿的明确遗传模型。西藏东南部爱罗山金矿带的新生代热液成因金矿床在遗传学上与变质的SCLM有关,而邻近的五叠纪灯泡岩堤被认为具有类似的来源,这为解决这一来源预算问题提供了难得的机会。利用有关灯泡岩长方体的嗜钠元素、熔体包裹体的挥发物含量及其全岩地球化学的综合数据,来确定它们与金矿床的共同来源。灯泡岩原生岩浆的特点是H2O(3.6 wt%)、Cl(高达4700 ppm)和S(高达3100 ppm)含量高,建模表明它们的地幔源也显著富含挥发性物质(H2O > 1000 ppm,Cl > 60 ppm),与地球上挥发性物质最丰富的岩浆和地幔内含物重叠。除去那些受到含金流体影响或经历过硫化物分离的岩峰,岩峰的金浓度不一,但一般正常(0.10-3.33 ppb),估计地幔来源的金浓度低于 1 ppb。这一范围低于全球地幔橄榄岩和原始上地幔的金含量,或与之相当,表明变质作用过程并没有使金矿区下方的SCLM明显富集异常的高金。因此,变质SCLM的高挥发物含量似乎在金矿床的形成过程中发挥了更为重要的作用,这种作用促进了含金流体的生成、矿石金属的提取、随后的流体转移和平流,而这种作用以前被低估了。
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来源期刊
Geochimica et Cosmochimica Acta
Geochimica et Cosmochimica Acta 地学-地球化学与地球物理
CiteScore
9.60
自引率
14.00%
发文量
437
审稿时长
6 months
期刊介绍: Geochimica et Cosmochimica Acta publishes research papers in a wide range of subjects in terrestrial geochemistry, meteoritics, and planetary geochemistry. The scope of the journal includes: 1). Physical chemistry of gases, aqueous solutions, glasses, and crystalline solids 2). Igneous and metamorphic petrology 3). Chemical processes in the atmosphere, hydrosphere, biosphere, and lithosphere of the Earth 4). Organic geochemistry 5). Isotope geochemistry 6). Meteoritics and meteorite impacts 7). Lunar science; and 8). Planetary geochemistry.
期刊最新文献
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