| 宁芜地区凹山地段旋扭构造控矿的研究 |
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| 引用本文：.1988.The ore-control mechanism of vortex structures in washan area of Nanjing-Wuhu region[J].Mineral Deposits,7(4):73~82 |
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| 中文摘要:本文从凹山地段各种旋扭构造与环状铁矿床的关系，探讨了旋扭构造对整个铁矿床形成的控制作用，并分析了控矿过程，指出了以往遵循的岩性、火山构造控矿理论的局限性，为进一步找矿开辟了一条新的思路。 |
| 中文关键词:旋扭构造 环状铁矿 楔状角砾岩带 隐蔽爆发角砾岩筒 |
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| The ore-control mechanism of vortex structures in washan area of Nanjing-Wuhu region |
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| Abstract:Washan area is the well-known locality of “porphyrite iron deposits” in middle and lower reaches of the Yangtze River. Most of the rich orebodies are distributed in circular pattern, obviously formed by ore-bearing solutions filling ring-shaped fissures or fracture zones. Much controversy exists concerntug the genesis of such kind of structural body. The main opinions include: (1) cupola-like fissures resulting from the difference between the surrounding pressure and the internal pressure of the magma; (2) cooling-contraction fissm es of the intrusions; (3) remnant paleovolcanic structures; and (4) attached structures of explosive breccia pipes. Since 1960s, according to the viewpoint of geomechanics, the author has made detailed investigation into five ore deposits and on such a basis, summarized the followtug basic facts: (1) There tmexceptionally exist well-developed schistose rock zones surrounding the ring-shaped or broom-like orebodies and, what is more interesting, some peculiar fissures have been observed, such as arc fissures, snail-shaped sliding surface and “8”-shaped fissures. (2) The center of the ring-shaped orebody or the convergent part of the broom-like ore veins contain mainly breccia bodies or brecciated ore bodies.(3) In some cases, sphenoidal breccia zones nearaly perpendicular to ring-shaped orebodies are seen, whose pinching-out end points to the center of the ringed vein.(4) Orebodies are thick, large and relatively rich at the center of the ring shaped ore veins or the convergent part of the broom-like ore veins, and gradually become thinner and poorer outwards. In addition, the regional joint measurement and the subsequent computer simulation of the ancient strain field demonstrate that the Washan area had the largest shear stress during the whole ore-forming epoch. Generally speaking, the unhomogeneous concentration of shear stress may result in the formation of vortex structure. It is inferred from the magnetic high upward continued to 5 km that there exists in the northwest part of the Washan area a concealed basic rock body a round which the main ore deposits and ore-bearing zones are arranged in turbine form along the vortex structure. As none of the above--mentioned opinions can explain satisfactorily these basic facts, the author considers that although not only the ring-like ore veins but also the whole orebodies have complex geneses, the vortex structures must have played the leading ore-controlling role. |
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