| 韧性剪切带中角砾状铅锌矿床的就位机制 |
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| 引用本文： | 刘俊来.韧性剪切带中角砾状铅锌矿床的就位机制[J].大地构造与成矿学,1993,17(2):135-145. |
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| 作者姓名： | 刘俊来 |
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| 摘 要： | 在辽吉岩套发育区识别出韧性剪切带内以围岩为角砾、铅锌硫化物为胶结物的角砾状矿化类型。矿体宏观形态简单而微细特点复杂,分别说明成矿裂隙兼具有压扭及张性特点。综合分析表明,成矿流体是高盐度卤水,重要意义在于它对铅锌成矿物质具高溶解度,携有足够量的成矿物质,它使先成矿体(化)中的铅、锌物质被淬取、活化和迁移。同时,对含矿裂隙的形成与发展有着促进意义。 角砾状矿体的出现与韧性剪切带晚期变形阶段岩石由韧性向脆性的转化有密切关系,在此过程中沿着Riedal裂隙系统的D裂隙系有铅锌成矿物质充填就位。Secor模式对角砾状矿体成矿空间的力学属性给出了很好的解释。液压扩容破裂作用是这种成矿空间产生与扩展的主要机制。
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| 关 键 词： | 就位机制 铅锌矿床 韧性剪切带 |
EMPLACEMENT MECHANISM OF BRECCIA Pb- Zn ORE DEPOSITS IN DUCTILE SHEAR ZONES |
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| Abstract: | A special type of Pb-Zn mineralization, i. e. breccia Pb-Zn sulphide mineralization in ductile shear zones, is recognized in the early Proterozoic carbonate rocks of the South Liaodong Peninsula, China. The mineralization is charactcrized by breccia orebodies with brecciated wallrocks cemented by sulphides. The shapes of the orebodies are simple in their overall configuration, but complex in detail. The simple overall configuration of orebodies are in the form of triaxial lenses with their AB planes (A,long axis and B,intermediate axis)parallel to the local mylonitic foliations of bedding-parallel shear zones. The orebodies pinch and swell laterally along the shear zones and the complex detailed shapes of ore units are controlled by the shapes of breccias and of the fractures. The ore-forming fractures originated under compressive shear which was followed by tension.The fluid phase that is active during the formation of breccia sulphides is a type of brine which plays an important role in the formation and evolution of the ore deposits. First, Pb-Zn elements have high solubility in such solutions, and so the latter carries sufficient mineralizing materials. Second, Pb-Zn elements in the primary orebodies are extracted, remobilized and transported by the fluuid phase. Furthermore, the formation and development of the ore-forming fractures are attributed to high-pressure fluids. The occunence of breccia orebodies is related to the S (or D) fractures in the Riedel systems formed in bedding-panallel shear zones when rocks are in the ductile-brittle transition. The mechanical properties of are-forming fractures are best interpreted by the Secor model with hydrsulic fracturing as the most important mechanism for these fractures. |
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| Keywords: | emplacement mechanism Pb-Zn ore deposit ductile shear zone |
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