Metallogenic Tectonic Analysis And Ore-finging Direction Of The Beiya Porphyry-type Gold Polymetallic Deposit In Northwestern Yunnan, China

The Beiya gold polymetallic deposit is one of the typical Cenozoic porphyry deposits in the Sanjiang polymetallic metallogenetic area, northwestern Yunnan province. In recent years, an important breakthrough has been achieved in the Beiya gold deposit prospecting which has made the Au reserves rank the superlarge class. This article uses the geomechanics theory and method of ore fields, through the large scale structural section precise measuring to analysis geometry、kinematics and tectonite characteristic of typical metallogenetic tectonics, and then to identify the mechanical properties and divide tectonic system. On these basis to establish mineralizing tectonic system、summary tectonic ore controlling regularity and to analyse the mechanism of the structural controlling of porphyry diagenesis and metallogenesis, and to establish tectonic ore controlling model.1、Tectonics are well developed in the Beiya deposit, which have the characteristics of multi period tectonic activity. The nearly SN trending Beiya syncline based folds and nearly SN trenging、nearly EW trenging based faults as high level control structures within the ore field, controlling the lormation and distribution of the porphyry and ore deposits (bodies), and the joints as a low level structures control the distribution of ore veins, reflecting tectonic control relationship in order, which constitutes a tapical folds-faults-joints rock and ore-forming tectonics system.2、Structures play a leading control function on the alkali rich porphyry emplacement and mineralization, according to different ore-controlling structures and mineralization features, the Beiya gold polymetallic bodies can be divided into five categories:1) controlled by faults, joint fissures porphyry body of porphyry type Au, Cu ore bodies; 2) controlled by the rock and contact zone of skarn type Au, Fe, Cu ore bodies; 3) controlled by the rock interlayer fracture zone, fault, joint fissure hydrothermal vein type Au, Fe ore bodies; 4) controlled by karst cave and unconformity contact oxidation leaching interface controlled enrichment type Au ore bodies; 5) controlled by the blasting breccia pipes of cryptoexplosion breccia type Au, Fe ore bodies;3、Since the late Yanshanian-early Himalaya, the main constructional compressive stress in the Beiya ore field has experienced the transition from near EW trending�' near SN trending �' near NW trending �' near EW trending, forming the South North tectonic belt、the East West tectonic belt and the North East tectonic belt, and respectively belongs to the Jinshajiang-Chenghai South North tectonic belt of the Sanjiang-Central Yunnan meridional tectonic system, the Tangdan-Heqing-Lanping East West tectonic belt of the Yunnan latitudinal tectonic system and the North East Lijiang tectonic belt;4、The ore controlling structural typies are mainly the "contact zone" ore controlling structure and "multi fonf"construction type in the Beiya gold field, which formed in the period when the East West tectonic belt that forming and developping in the middle of Himalaya. The East West tectonic belt is the dominant tectonic system that controlling large-scale porphyry-skarn-hydrothermal vein type-cryptoexplosion breccia type deposits, the former North South tectonic belt formed in the early Himalaya provids a favorable structural environment for the porphyry emplacement and gold mineralization, and the later North South tectonic belt is the dominant tectonic system which controlling oxidation leaching enrichment type deposits in late Himalaya.5、Though the analysis on the regularity of structural ore control and the establishment of structural ore controlling model, considering that the contact zone structure、the interlayer fracture zone and the near SN trending extension faults and joints are favourable prospecting sites, and it has a great prospecting potential in the Tanyao area in the north of the Beiya gold polymetallic deposit...