Origin of the Jiaodong-type Xinli gold deposit, Jiaodong Peninsula, China: Constraints from fluid inclusion and C-D-O-S-Sr isotope compositions
Origin of the Jiaodong-type Xinli gold deposit, Jiaodong Peninsula, China: Constraints from fluid inclusion and C-D-O-S-Sr isotope compositions
复制标题
胶东半岛胶东型新立金矿成因：流体包裹体及C-D-O-S-Sr同位素组成的制约
DOI：
10.1016/j.oregeorev.2014.04.018
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发表时间：
2015
影响因子：
3.3
通讯作者：
Pan RG
中科院分区：
文献类型：
--
作者：
Deng J;Liu XF;Wang QF;Pan RG
胶东金矿区三山岛-仓上金矿带内的新立金存款是一个典型的“焦家式”金存款矿床。矿石可分为四个阶段：Ⅰ）石英-钾长石-绢云母-黄铁矿; Ⅱ）石英-黄铁矿; Ⅲ）石英-多金属硫化物; Ⅳ）石英-方解石-黄铁矿。矿石中石英和方解石包裹体中的流体以C-O-H流体为主，主要有6种类型，其液汽比各不相同。主成矿期成矿流体具有中低温、低盐度、还原性、NaCl-H2O-CO2± CH 4的特征。Ⅱ、Ⅲ期石英的δ 18 O水（‰）SMOW为2.82 ~ 5.34‰，δD（‰）SMOW为− 69.6 ~ 88.3‰。两者均表明成矿流体以岩浆水为主。方解石的δ 13 CPDB值介于-6.4 ‰ ~-2.4 ‰之间，反映了地幔对成矿流体的贡献。4个成矿阶段黄铁矿δ 34 SCDT值基本相似，变化范围为9.42 ~ 11.62‰，反映了地壳物质的参与。方解石中87 Sr/86 Sr的初始比值为0.710657 ~ 0.711542，也表明了地壳的贡献。流体组成和H-O-C-S-Sr同位素数据的系统解释为板状俯冲诱发金成矿模式。在该模型中，成矿流体和金属被认为与俯冲的古太平洋板片的脱水和脱水作用以及随后的富集地幔楔的脱挥发分作用有关。流体中的H2O可能来自富集地幔楔的脱挥发分作用，CO2可能来自地幔楔或陆下岩石圈地幔，而硫和锶则可能来自俯冲海底沉积物。与金矿床同生的中基性岩脉的地球化学特征进一步支持了这一过程。新立金存款矿床的存款特征和成矿作用与造山型金存款和与岩体有关的金存款矿床的特征和成矿作用不一致。研究结果支持胶东金矿床属于与复杂板片俯冲作用有关的独特金矿床类型的观点。胶东式金存款的地球动力学机制是独特的，板片俯冲耦合随之而来的岩石圈减薄和结构调整。
The Xinli gold deposit within the Sanshandao–Cangshang gold belt in the Jiaodong gold province is a typical “Jiaojia type” ore deposit, with high-grade, quartz–sulfide vein/veinlet stockworks that cut Mesozoic granodiorite. Four ore stages are distinguished in the following sequences: I) quartz–K–feldspar–sericite–pyrite; II) quartz–pyrite; III) quartz–polymetallic sulfide; and IV) quartz–calcite–pyrite. Fluid inclusions in quartz and calcite in the ores contain C–O–H fluids dominantly of six types with varied liquid/vapor ratio. Ore fluid in the main ore stage is characterized by medium–low temperature, low salinity, reducing condition, and NaCl–H2O–CO2± CH4in composition. The δ18Owater(‰)SMOWof quartz in ore stages II and III range from 2.82 to 5.34‰, and the δD (‰)SMOWare between − 69.6 and 88.3‰. Both suggest that the ore fluid was dominantly magmatic water. The δ13CPDBof the calcite are from − 6.4‰ to − 2.4‰, indicating mantle contribution to the ore fluid. The pyrite δ34SCDTfrom four ore stages are basically similar varying from 9.42 to 11.62‰, which implies significant involvement of crustal materials. The initial87Sr/86Sr ratios in the calcite ranging from 0.710657 to 0.711542 also denote a crustal contribution. The fluid composition and systematic H–O–C–S–Sr isotopic data are explained by a model of slab-subduction induced gold mineralization. In the model, the ore fluid and metals were considered to associate with the dehydration and desulfidation of the subducting paleo-Pacific slab and the subsequent devolatilization of enriched mantle wedge. The H2O in the fluid might have been released from the devolatilization of enriched mantle wedge; the CO2could be from mantle wedge or subcontinental lithospheric mantle; and the sulfur and strontium would be initially released from the subducted seafloor sediments. This process was further supported by the geochemical features of intermediate-basic dykes contemporaneous to the gold ore deposits. The deposit features and ore-forming process of the Xinli gold deposit hardly concur those of the orogenic gold deposit and the pluton-related gold deposit. The study supports the argument of that the gold deposits in the Jiaodong belong to a unique gold type related to a complex slab subduction-related process. The geodynamic engine of the Jiaodong-type gold deposit is specific, i.e., the slab subduction coupling with the consequent lithospheric thinning and structure adjustment.