Origin and formation of carbonaceous material veins in the 2008 Wenchuan earthquake fault zone
Origin and formation of carbonaceous material veins in the 2008 Wenchuan earthquake fault zone
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2008年汶川地震断裂带碳质物质脉的起源与形成
DOI：
10.1186/s40623-016-0399-z
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
Bo Zhang
中科院分区：
文献类型：
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作者：
Jiang Liu;Haibing Li;Jinjiang Zhang;Bo Zhang
本文建立了一个参考数据集的含碳物质（CM）从龙门山断裂带的活动断裂带，在2008年Mw7.9汶川地震破裂，并提出了这些数据的应用研究的其他掘出的富碳断裂带和深钻芯。活动断裂带中的CM呈窄脉状分布，沿着滑面分布。显微构造观察表明，断层泥带中碳质物质脉（CMVs）沿着滑动面分布。一些CMVs具有碎裂组构，其分支侵入滑动面周围的空隙中。CMVs的拉曼光谱显示在~1345 cm-1处的宽（半高全宽>200 cm-1）D-峰（缺陷峰），其远低于在~1595 cm-1处的O-峰（有序峰），表明沸石相的变质温度或低于250 °C。此外，其稳定碳同位素组成（δ 13 C值）与四川盆地晚三叠世须家河组干酪根的稳定碳同位素组成（δ 13 C值）非常相似，变化范围为−23.4 ‰ ~ −26.4‰。鉴于其可能形成的数据，须家河组是CMVs最有可能的CMs起源，并且似乎断裂带中的一些CMVs在同震事件期间被压碎并侵入空隙中，可能是由增强的孔隙流体压力驱动的。由于石墨化被认为是该地区瞬态摩擦加热的一个指标，我们的研究提供了一个参考数据集的CM将有助于未来的CM丰富的断裂带的研究，以检索可能发生在龙门山断裂带的地震信号。
This paper establishes a reference data set of carbonaceous materials (CMs) from the active fault zone of the Longmen Shan fault belt that ruptured in the 2008 Mw7.9 Wenchuan earthquake and presents an application of these data for studies of both other exhumed carbonaceous-rich fault zones and deep-drilling cores. The CMs distributed in the active fault zone are found as narrow veins and located along the slip surfaces. Microstructural observation shows that the carbonaceous material veins (CMVs) are located along slip surfaces in the fault gouge zones. Some CMVs have a cataclastic fabric, and their branches intrude into voids around the slip surfaces. Raman spectra of the CMVs show a wide (full width at half maximum >200 cm−1) D-peak at ~1345 cm−1(defect peak), which is much lower than the O-peak at ~1595 cm−1(ordered peak), indicating a metamorphic temperature of zeolite facies or lower than 250 °C. In addition, the stable carbon isotopic compositions (δ13C values) of the CMVs, ranging from −23.4 to −26.4‰, are very similar to that of the kerogen collected from the Late Triassic Xujiahe Formation in Sichuan Basin. Given the data at which it may be formed, the Xujiahe Formation is the most likely origin of CMs for the CMVs, and it seems that some CMVs in the fault zone were crushed and intruded into the voids during coseismic events, possibly driven by an enhanced pore fluid pressure. Since graphitization is suggested as an indicator of transient frictional heating in this area, our study providing a reference data set of CMs would help future CM-rich fault-zone research to retrieve seismic signatures presumably occurring in the Longmen Shan fault zone belt.