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51.
Li Haibing Yang Jingsui Xu Zhiqin Wu Cailai Zhang Jianxin Wan Yushen Shi Rendeng Juhn G. Liou Trevor R. Ireland 《地学前缘》2000,(Z1)
AGE OF THE ALTYN TAGH STRIKE—SLIP FAULT 相似文献
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河台金矿田是广东省内规模最大的金矿,由于金矿床都产于糜棱岩带中,因而被认为是典型的与剪切带有关的金矿。然而,对于Au矿化与剪切带变形条件之间的关系目前仍不十分清楚。高村和云西是河台金矿田两个代表性的金矿床,分别受ML11和ML9两条剪切带的控制。本文在对两条剪切带中的含矿和无矿糜棱岩的变形特征进行野外调查和室内岩(矿)相学观察的基础上,分别开展岩石磁学和磁化率各向异性(AMS)特征研究。糜棱岩x- T曲线显示了磁黄铁矿的居里温度,结合磁滞回线、等温剩磁(IRM)以及矿相学特征,表明河台金矿田糜棱岩几乎不含磁铁矿,载磁矿物主要为黑云母和磁黄铁矿,但是磁黄铁矿的贡献要远大于黑云母。两条糜棱岩带中不含矿糜棱岩的平均磁化率Km<500×10-6 (SI)、磁化率各向异性度Pj、椭球体形状参数T、磁面理F和磁线理L没有明显差别。并且形成两条剪切带的主应力方向也近于一致,最大主应力方向σ1(K3)为近水平NNW- SSE向,最小主应力σ3(K1)为NEE- SWW向,倾伏角较缓。运动学涡度Wk值也近似,在0. 12~0. 65之间,小于0. 71。上述特征暗示两条含金剪切带都是在印支期NNW- SSE向近水平的强烈挤压作用下形成的,其中发育的糜棱岩为S型和SL型构造岩,具有强烈压扁的特征,并且在剪切变形过程中纯剪切作用所占的比重要明显大于简单剪切。然而,两条剪切带中含矿糜棱岩与无矿糜棱岩的AMS特征有明显的区别。含矿糜棱岩的K1近于直立,且Km>500×10-6 (SI)和Pj值都明显大于无矿糜棱岩。因此,糜棱岩的变形强度与含矿性具有一定的正相关关系,而在燕山期叠加的脆韧性变形使得最大磁化率主轴(即最小主应力轴)变陡,更有利于热液的运移和最终成矿。 相似文献
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Abstract The Shangdan fault in the Qinling Orogenic Belt of China is an important boundary between the Caledonian North Qinling Fold Belt and the Hercynian South Qinling Fold Belt. In the Danfeng area, the fault zone strikes WNW–ESE and comprises four strongly deformed zones and three weakly deformed domains parallel to each other. The fault zone has a complex history of multiple deformation and each domain has a different tectonic style that was formed at different stages of the deformation.
The rocks exposed in the weakly deformed domains belong to the Qinling, Danfeng and Liuling Groups. In this paper, the mineral chemistry and mineral assemblages are used to infer the metamorphic conditions and the P–T paths of these units. The metamorphic units in and near the fault zone have different metamorphic conditions and histories that are correlated with the tectonic evolution of the fault zone. Caledonian–Hercynian uplift and southward thrusting of the Proterozoic Qinling Group, over the Danfeng and the Liuling Groups, produced the main metamorphic and tectonic features of the fault zone. Folding of both the Liuling Group and the thrust faults during the Hercynian–Indosinian was accompanied by northward thrusting. 相似文献
The rocks exposed in the weakly deformed domains belong to the Qinling, Danfeng and Liuling Groups. In this paper, the mineral chemistry and mineral assemblages are used to infer the metamorphic conditions and the P–T paths of these units. The metamorphic units in and near the fault zone have different metamorphic conditions and histories that are correlated with the tectonic evolution of the fault zone. Caledonian–Hercynian uplift and southward thrusting of the Proterozoic Qinling Group, over the Danfeng and the Liuling Groups, produced the main metamorphic and tectonic features of the fault zone. Folding of both the Liuling Group and the thrust faults during the Hercynian–Indosinian was accompanied by northward thrusting. 相似文献
56.
敦密断裂带走滑运动的^40Ar/^39Ar年代学证据 总被引:4,自引:0,他引:4
敦密断裂带是郯庐断裂带北段最重要的分支,其大规模左旋走滑剪切时代一直是悬而未决的科学问题。野外构造解析和显微构造分析表明,密山县知一镇附近的敦密韧性剪切带为左旋剪切带,变形温度约450~650℃。在韧性剪切带糜棱岩中获得黑云母单矿物的40Ar/36Ar-39Ar/36Ar等时线年龄值为(161±3)Ma,结合完达山地体的走滑拼贴时代,认为敦密断裂带在中侏罗世末期发生强烈的左旋走滑运动。这一年代学数据反映了在滨太平洋构造域构造活动期间,郯庐断裂被利用而再次发生左旋走滑,并向北扩展到东北地区。敦密断裂走滑运动时代与完达山地体的走滑-拼贴增生时代吻合,两者是相同大地构造背景中的产物。 相似文献
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以排山楼金矿床和八亩地金矿点为例,总结了华北陆台北缘韧性剪切糜棱岩型金矿的地质特征:①地处地体边界的多期复杂活动带;②韧脆性剪切富集金,矿化局限于糜棱岩内;金矿与韧性剪切糜棱岩二者同生;③含金纹带状集合体组成主要为细粒石英和黄铁矿;④矿体呈透镜状,金的集合体在糜棱岩中与糜棱面理呈整合关系;⑤矿石主要组分不是简单的裂隙充填物,而是动态重结晶的产物,表明成矿是活化或复活的韧性剪切作用的产物;⑥蚀变为弱绢云母化、绿泥石化和碳酸盐化. 相似文献
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Abstract Mylonites along the Median Tectonic Line, southwest Japan commonly contain shear bands comprising S(-C)-Ss fabrics. This paper stresses the lithologic control on the orientation, dimension and development of shear bands by comparing the microstructure of the shear bands in different rock types (P mylonites, F mylonites, micaceous phyllonite and quartzose phyllonite). There is no significant change of the α angles (average 21–24°) between Ss and S toward the centre of the shear zone (viz. increasing the intensity of mylonitization) and it is different from the S-C relationship in a narrow sense.
The generation of the composite planar fabric can be classified into four different strain partitioning models: S only type without any slip surface (model A); S-C type (model B); S-Ss type with Ss-slip precedence (model C), and S-Ss type with S-slip precedence (model D). Model C is proposed in this paper and is similar to the model for the generation of Riedel shears in brittle shear zones. An unstable slip between porphyroclasts and the matrix during ductile flow can easily initiate shear bands. Formation of a composite planar fabric is initiated according to model A, followed by model C in conditions of increasing strain, and then model D when the angle between S and the shear zone boundary becomes small enough (α/2 = 10°) to produce S-slip. Thus the generation of the shear bands probably begins in the early stages of shear deformation and continues until the latest stages. 相似文献
The generation of the composite planar fabric can be classified into four different strain partitioning models: S only type without any slip surface (model A); S-C type (model B); S-Ss type with Ss-slip precedence (model C), and S-Ss type with S-slip precedence (model D). Model C is proposed in this paper and is similar to the model for the generation of Riedel shears in brittle shear zones. An unstable slip between porphyroclasts and the matrix during ductile flow can easily initiate shear bands. Formation of a composite planar fabric is initiated according to model A, followed by model C in conditions of increasing strain, and then model D when the angle between S and the shear zone boundary becomes small enough (α/2 = 10°) to produce S-slip. Thus the generation of the shear bands probably begins in the early stages of shear deformation and continues until the latest stages. 相似文献
59.
金厂峪韧性剪切带具有多期多阶段长期演化历史,可以划分为两期变形。早期变形是塑性变形,主要形成各种类型糜棱岩,是等化学变形。晚期变肜作用是韧脆性变形,主要形成片糜岩,是非等化学变形。在晚期变形过程中SiO_2和金等成矿元素从围岩中所出,然后迁移至低压空间沉淀成矿,表明成矿作用和晚期韧性变形作用是同时发生的。 相似文献
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山东省烟台市双山屯金矿产于牟平—朱吴断裂的构造破碎带中,与区域金矿的特征相似,金矿体严格受断裂的控制。深部的金矿体主要有Ⅱ-7号和M7号矿体,金矿体在空间上呈舒缓波状,并向E侧伏;断裂控制了围岩蚀变的范围、形态和分带,也控制着矿体的产状、形态,使蚀变和金矿化具有时空的一致性。勘查结果表明,深部的金矿体在产状、矿石类型等方面出现了明显变化,在-900m标高以下并未封闭,仍有向深部延伸的可能,因此要注意已知矿体边部和深部的找矿;控矿断裂在晚中生代经历了多次性质的活动,但金的成矿只是在断裂活动的特定时段发生,即早白垩世晚期(130~110 Ma)的张扭活动,该期断裂活动提供了成矿所需的运移通道和储矿空间。 相似文献