The Relationships between Tectonic Movements and the Fluid Flow in Dabashan Fold and Thrust Belt in China

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• 作者：De-Zhi Huang^a ; ^{dzhuang@mail.csu.edu.cn} ; ^{Dzhuang_01@163.com} ; Xian-Ying Wang^a ; Guo-Ming Li^a ; Zhen Liu^a ; Ze-hua Peng^a ; Shi-Qi Huang^b ; ^c ; ^{qi283463544@163.com} ; Wei Shi^b ; ^c ; Shu-Wen Dong^c
• 关键词：Generations of veins ; Fluid inclusions ; Stable isotopes ; Paleostress states ; Dabashan Thrust and Fold Belt
• 刊名：Procedia Environmental Sciences
• 出版年：2012
• 出版时间：2012
• 年：2012
• 卷：12
• 期：part_PA
• 页码：672-686
• 全文大小：1556 K

文摘

Three generations of calcite veins filling in fractures have been recognized in Dabashan Thrust and Fold Belt in China. Reconstruction of the paleostress states corresponding to and studies on fluid inclusions and stable isotopes from the wall-rocks and the veins filled in the fractures have been carried out. The first vein, which occurs in the fractures limited to competent bed and perpendicular to the layer, was precipitated from liquids during diagenesis. Homogenization temperatures (Th) of fluid inclusions in the veins range from 126¡ãC to 267¡ãC, which are similar to those obtained by the wall-rocks, i.e., from 152¡ãC to 227¡ãC. The second-generation veins were filled in three groups of faults corresponding to NE-SW compression. Homogenization temperatures of the fluid inclusions show bimodal distribution, with peak Th-population values from 140¡ãC to 210¡ãC and 230¡ãC to 270¡ãC. The salinity values exhibit evidently two groups either. The bimodal distribution of both homogenization temperatures and salinities indicates that the fluid flowing within the fractures posses two stages of evolution. The third-generation vein was filled in NNW-SSE to NWW-SEE trending strike-slip faults, which were formed under NW-SE tectonic compression. The homogenization temperatures obtained by fluid inclusions in the veins range from 101¡ãC to 257¡ãC. The wide change in Th values possibly indicates that re-equilibrium has occurred for the fluid inclusions during the activity of the faults.

The ¦Ä¹³C and ¦Ä¹⁸O values of the wall rocks range from -1.6?to 5.6?and 16.7?to 25.2? respectively. The values of ¦Ä¹⁸O are similar to or lower slightly than marine carbonate(29?. The ¦Ä¹³C and ¦Ä¹⁸O values of the first-generation veins are from -1.8?to 2.2?and 18.4?to 23.1? respectively, which are similar to those of wallrocks except showing smaller variation. The ¦Ä¹³C and ¦Ä¹⁸O values of the second-generation veins range from -9.2?to 4.7?and 13.2?to 27.9? Compared to wallrocks and the first-generation veins, the second-generation veins exhibit larger variability in both ¦Ä¹³C and ¦Ä¹⁸O values. The third-generation veins show similar situation to the second-generation veins in ¦Ä¹³C values and the large variation in carbon isotopic compositions with the ¦Ä¹³C values from -9.2?to 4.8? But the ¦Ä¹⁸O values are not as large variable as that of the second-generation veins, and the ¦Ä¹⁸O values are from 12.8?to 19.8? The ¦ÄD values measured by fluid inclusions from the second- and third-generation veins are from -62?to -90?and -74?to -87? respectively. On the plot of ¦Ä¹⁸O_fluids vs ¦ÄD_fluids, parts of samples are fall in the scope of formation water, some samples show slightly lower ¦ÄD values relative to formation water.