郭瑾, 闫小兵, 李自红, 陈慧, 扈桂让. 2019: 汶川地震断层带中碳酸盐岩碳氧同位素分异——对断层愈合机制的启示. 地质通报, 38(6): 959-966.
    引用本文: 郭瑾, 闫小兵, 李自红, 陈慧, 扈桂让. 2019: 汶川地震断层带中碳酸盐岩碳氧同位素分异——对断层愈合机制的启示. 地质通报, 38(6): 959-966.
    GUO Jin, YAN Xiaobing, LI Zihong, CHEN Hui, HU Guirang. 2019: Carbon and oxygen isotope fractionation of carbonate rocks in the fault zone of Wenchuan earthquake:Implications for the mechanism of fault healing. Geological Bulletin of China, 38(6): 959-966.
    Citation: GUO Jin, YAN Xiaobing, LI Zihong, CHEN Hui, HU Guirang. 2019: Carbon and oxygen isotope fractionation of carbonate rocks in the fault zone of Wenchuan earthquake:Implications for the mechanism of fault healing. Geological Bulletin of China, 38(6): 959-966.

    汶川地震断层带中碳酸盐岩碳氧同位素分异——对断层愈合机制的启示

    Carbon and oxygen isotope fractionation of carbonate rocks in the fault zone of Wenchuan earthquake:Implications for the mechanism of fault healing

    • 摘要: 汶川地震断层带北川擂鼓镇赵家沟剖面的露头及显微结构均发现多期次脉体纵横交错,角砾岩被胶结。通过对断层岩相关的碳酸盐矿物同位素分析得知,断层岩角砾和脉体中大量的白云石来源应是断层带内富Mg离子的流体,且碳氧同位素显著分异,角砾的δ18O值和δ13C值与灰岩围岩更接近,脉体和基质显示重同位素亏损。通过“同震热分解”和“水-岩相互作用”2种可能模型的研究分析,同震热分解模型δ13C值明显高于实际,而水-岩相互作用则可形成这种分异结果。故震后深部流体上涌所导致的表层大气水再循环可能是导致震后断层快速愈合的重要原因,同震破裂和间震期愈合则形成完整的断层系统。

       

      Abstract: The outcrop and microscopic structure analysis of Zhaojiagou section at Leigu Town in Beichuan area of Wenchuan earthquake fault zone revealed that multi-phase veins crisscross and the breccia has been cemented.The isotope analysis of carbonate minerals related to fault rocks shows that the source of a large amount of dolomite in the fault breccia and veins should be the Mgrich fluid in the fault zone, and the carbon and oxygen isotopes exhibit significant differentiation.The δ18O and δ13C values of breccia are more close to values of surrounding rocks of limestone, and the veins and matrix exhibit heavy isotope losses. It is found that the δ13C values of the coseismic thermal decomposition model is obviously higher than the real values and the water-rock interaction model can form this differentiation result, as shown by comparison of these two possible models.Therefore, the surface water recirculation caused by the upwelling of deep fluids may be the significant cause of the fault rapid healing after earthquake. The coseismic rupture and inter-seismic healing form a complete fault system.

       

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