Water—Rock Interactions and Chemical Compositional Variations During Ductile Deformation of the NW—Striking Shear Zone in te Jiapigou Gold Belt,China |
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引用本文: | 孙晓明,徐克勤,等.Water—Rock Interactions and Chemical Compositional Variations During Ductile Deformation of the NW—Striking Shear Zone in te Jiapigou Gold Belt,China[J].中国地球化学学报,1996,15(4):331-341. |
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作者姓名: | 孙晓明 徐克勤 |
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作者单位: | [1]GeologyDepartmentofZhongshanUniversity,Guangzhou,510275 [2]DepartmentofEarthSciences,NanjingUniversity,N |
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摘 要: | Two kinds of mylonite series rocks,felsic and mafic,have been recognized in the NW-striking shear zone of the Jiapigou gold belt.During ductile deformation, a large amount of fluid interacted intensively with the mylonite series rocks:plagioclases were sericitized and the An values declined rapidly,finally all of them were transformed to albites;dark minerals were gradually replaced by chlorites(mostly ripidolite).Meanwhile,large-scale and extensive carbonation also took place,and the carbonatization minerals varied from calcite to dolomite and ankerite with the development of deformation.Theδ^13 Cvalues of the carbonates are-3.0‰--5.6‰suggesting a deep source of carbon.The ductile deformation is nearly an iso-volume one(fv=1).With the enhancement of shear deformation,SiO2 in the two mylonite series rocks was depleted,while volatile components such as CO2 and H2O,and some ore-forming elements such as Au and S were obviously enriched.But it is noted that the enrichment of Au in both the mylonite series rocks did not reach the paygrade of gold.The released SiO2 from water-rock interactions occurred in the form of colloids and absorbed gold in the fluid.When brittle structures were formed locally in the ductile in the ductile shear zone,the ore-forming fluids migrated to the structures along microfractures,and precipitated auriferous quartz because of reduction of pressure and temperature.Fluid inclusion study shows that the temperature and pressure of the ore-forming fluids are 245-292℃and 95.4-131.7MPa respectively;the salinity is 12.88-16.33wt% NaCl;the fluid-phase is rich in Ca^2 ,K^ ,Na^ ,Mg^2 ,F^- and Cl^-,while the gaseous phases are rich in CO2 and CH4.The δD and δ^18O values of the ore-forming fluid are -84.48‰--91.73‰and -0.247‰- 2.715‰respectively,suggesting that the fluid is composed predominantly of meteoric water.
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关 键 词: | 水岩反应 流体地球化学 金矿带 化学组成 氧同位素 成矿元素 |
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