耿马帚状构造的基本轮廓及其找矿意义

帚状构造是扭动构造型式之一。该构造在西起孟定—云县一线,东到勐永—木戛—澜沧一线,北起云县县城附近,南经沧源一带入缅甸玉勒和中国西盟一带,总面积约一万三千余平方公里,收敛于耿马北东的勐永一带,向西南方向的缅甸及中国的西盟一带撒开。其主体属云南省临沧地区云县、耿马县,沧源县和思茅地区西盟县所辖。前人资料把该区统归于南北向构造带。建国以来,该区曾先后开展了一比一百万和一比十万区调及钨、锡、铜、铅、锌等多金属及金、银等贵金属矿床的普查找矿工作,取得了丰富的地质资料。最近又找到了大型的西盟富锡矿床和耿马地区金银矿带及铜、铅、锌等矿点。该区的背向斜和断裂构造及

BASIC CONFIGURATION OF THE GENGMA BRUSH STRUCTURE AND ITS SIGNIFICANCE FOR MINERAL PROSPECTING

The study and determination of the Gengma brush structural type contained in the western Yunnan meridional structure are of great geological significance for studying the crustal movements,direction and mode of the stress action,magmatism and metamorphism in various times and formation and distribution of ore deposits in western Yunnan. The Gengma brush structural type has been defined through many years of mineral prospecting and by applying the geomechanic view-point and method. The Gengma brush structure consists of a series of compresso-shear faults and axial surfaces of folds.They are distributed in a vast area east of Mengding-Yunxian,west of Yunxian-Daxing-Muga and north of Ximeng （including the Mandon-Yishi area of northeast Burma）.The generation of the Gengma brush structure has a close genetic connection with the generation and development of the NE-trendingMengding-Yunxian fault.Therefore,the stress tnansformation of the Mengding-Yunxian fault is bound to bring about changes of the brush structure. As the Mengding-Yunxian fault has mainly undergone the meridional compression （which last the longest and acted the strongest）,the area where the Gengma brush structure lies is in the main in the compresso-shear stress field and in the state of counterclockwise shearing. The Gengma brush structure,especially its middle and southern sectors,has an important controlling effect on polymetallic ore deposits in Gengma,Changyuan and Ximeng. So mineral prospecting work in this area should be strengthened in the future,which will lead to the discovery of more and richer tungsten,tin,gold and silver deposits for the country.