Mantle heat drives hydrothermal fluids responsible for carbonate-hosted base metal deposits: evidence from 3He/4He of ore fluids in the Irish Pb-Zn ore district
Mantle heat drives hydrothermal fluids responsible for carbonate-hosted base metal deposits: evidence from 3He/4He of ore fluids in the Irish Pb-Zn ore district
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DOI：
10.1007/s00126-014-0516-5
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发表时间：
2014-04
影响因子：
4.8
通讯作者：
B. Davidheiser-Kroll;F. Stuart;A. Boyce
中科院分区：
文献类型：
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作者：
B. Davidheiser-Kroll;F. Stuart;A. Boyce
对于碳酸盐赋存的贱金属矿床，如世界级的爱尔兰锌铅矿田，是在碰撞构造环境中形成的，还是在伸展构造环境中形成的，人们几乎没有达成共识。对爱尔兰锌铅矿田主要贱金属矿床硫化物样品中捕获的成矿流体中的氦同位素进行了分析，以量化需要熔融才能实现的地幔挥发分的参与程度，并测试了矿田成因的主流模式。3He/4He比值高达0.2Ra，表明捕获在方铅矿和大理石中的成矿流体中存在少量但清晰的地幔氦贡献。流体包裹体温度最高(~200℃)的矿床的硫化物也具有最高的3He/4He(>；0.15Ra)。类似的3He/4He记录在正在经历活动伸展的现代大陆地区的流体中。通过类比，我们认为负责碳酸盐赋存的爱尔兰贱金属成矿的热液流体在经历了伸展的变薄的陆壳中循环，并证明了地幔热流的增强是驱动流体对流的最终原因。
There is little consensus on whether carbonate-hosted base metal deposits, such as the world-class Irish Zn + Pb ore field, formed in collisional or extensional tectonic settings. Helium isotopes have been analysed in ore fluids trapped in sulphides samples from the major base metal deposits of the Irish Zn-Pb ore field in order to quantify the involvement of mantle-derived volatiles that require melting to be realised, as well as test prevailing models for the genesis of the ore fields.3He/4He ratios range up to 0.2Ra, indicating that a small but clear mantle helium contribution is present in the mineralising fluids trapped in galena and marcasite. Sulphides from ore deposits with the highest fluid inclusion temperatures (~200 °C) also have the highest3He/4He (>0.15Ra). Similar3He/4He are recorded in fluids from modern continental regions that are undergoing active extension. By analogy, we consider that the hydrothermal fluids responsible for the carbonate-hosted Irish base metal mineralization circulated in thinned continental crust undergoing extension and demonstrate that enhanced mantle heat flow is ultimately responsible for driving fluid convection.