Abstract Graphitic carbon-bearing rocks generally occur in low-to high-grade metamorphic units. In many brittle faults, graphitic carbon is often associated with gouge or low-grade metamorphic rocks whereas in ductile faults, graphitic carbon commonly occurs in marble, schist or gneiss. Carbonaceous material gradually transforms from an amorphous into an ordered crystalline structure by increasing thermal metamorphism. The degree of graphitization is believed to be a reliable indicator of peak temperature conditions in the metamorphic rock. In this contribution, based on detailed field observations, the variably deformed and metamorphosed graphitic gneisses to phyllites, located within the footwall and hangingwall unit of the Cenozoic Ailaoshan-Red River strike-slip shear zone are studied. According to lithological features and temperatures determined by Raman spectra of carbonaceous material, these graphitic rocks and deformation fabrics are divided into three types. Type I is represented by medium-grade metamorphism and strongly deformed rocks with an average temperature of 509 °C and a maximum temperature of 604 °C. Type II is affected by low-grade metamorphism and deformed rocks with an average temperature of 420 °C. Type III is affected by lower-grade metamorphism and occurs in weakly deformed/undeformed rocks with an average temperature of 350 °C. Slip-localized micro-shear zones and laterally continuous or discontinuous slip-planes constituted by graphitic carbon aggregates are developed in Types I and II. The electron back-scattered diffraction (EBSD) lattice preferred orientation (LPO) patterns of graphitic carbon grains were firstly observed in comparison with LPO patterns of quartz and switch from basal , rhomb to prism slip systems, which indicate increasing deformation temperatures. Comparison of quartz and graphite LPOs indicates that graphite LPOs show higher temperature conditions. According to the graphitic slip-planes, micro-shear zones with grain-size reduction and mylonitic foliation constituted by graphitic carbon minerals, we also propose that the development of fine-grained amorphous carbon plays an important role in rheological weakening of the whole rock during progressive ductile shearing.

中文翻译：

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哀牢山-红河走滑断裂带石墨含碳岩的变形结构及应变定位机制

摘要 石墨质含碳岩一般出现在低至高品位变质单元中。在许多脆性断层中，石墨碳通常与凿岩或低品位变质岩有关，而在韧性断层中，石墨碳通常存在于大理石、片岩或片麻岩中。碳质材料通过增加热变质作用逐渐从无定形转变为有序的晶体结构。石墨化程度被认为是变质岩中峰值温度条件的可靠指标。在此贡献中，基于详细的现场观察，研究了位于新生代哀牢山-红河走滑剪切带下盘和上盘单元内的可变变形和变质的石墨片麻岩到千枚岩。根据碳质材料的拉曼光谱确定的岩性特征和温度，将这些石墨岩和变形组构分为三种类型。Ⅰ型以中变质、强变形岩体为代表，平均温度509℃，最高温度604℃。II型受低变质作用和变形岩影响，平均温度为420℃。III型受低级变质作用影响，发生在弱变形/未变形岩石中，平均温度为350°C。由石墨碳聚集体构成的滑移局部微剪切带和横向连续或不连续的滑移面在 I 型和 II 型中发育。首次观察到石墨碳颗粒的电子背散射衍射 (EBSD) 晶格择优取向 (LPO) 图案与石英的 LPO 图案相比，并从基底、菱形向棱柱滑移系统转变，这表明变形温度增加。石英和石墨 LPO 的比较表明石墨 LPO 显示出更高的温度条件。根据石墨碳矿物构成的石墨滑移面、粒度减小的微剪切带和糜棱片理，我们还提出细粒无定形碳的发育在整个岩石流变弱化过程中起着重要作用。渐进塑性剪切。这表明变形温度增加。石英和石墨 LPO 的比较表明石墨 LPO 显示出更高的温度条件。根据石墨碳矿物构成的石墨滑移面、粒度减小的微剪切带和糜棱片理，我们还提出细粒无定形碳的发育在整个岩石流变弱化过程中起着重要作用。渐进塑性剪切。这表明变形温度增加。石英和石墨 LPO 的比较表明石墨 LPO 显示出更高的温度条件。根据石墨碳矿物构成的石墨滑移面、粒度减小的微剪切带和糜棱片理，我们还提出细粒无定形碳的发育在整个岩石流变弱化过程中起着重要作用。渐进塑性剪切。