Studying On Evolution And Metallogenic Regularity And Ore-Prospecting Direction Of The Jiangda Tectonic Belt, East Tibet, SW China

This paper discusses the evolution, metallogenic law, and ore-prospecting direction about the Jiangda tectonic belt, by studying tectonic evolution and tectonics-metallogeny coupling relationship, guiding by theories of terrane-plate tectonics and tectonics-metallogeny, basing on the thought that different tectonic regime has different geologic-metallogenesis, and the conversion of multiple tectonic regimes conduces certainly to the generalized homothetic composite action of multiple metallogenic subsystems, and forming the multiple-composite metallogenic system.Jiangda tectonic belt lies in the north of the Three-rivers (Nujiang, Lancangjiang, and Jinshajiang) Tectonic Belt, SW China; the east of Changdu massif; the west of Jinshajiang faults zone.The Independent Jiangda tectonic belt has appeared since late Carboniferous, following the Jinshajiang ocean crust of subducted beneath the Changdu continental crust and the continental margin arc formed in east of Changdu terrane.Jiangda tectonic belt experienced three tectonic regimes transform since it had come into being: 1. Continental margin arc regime of ocean-continental process (C3~T2) ; 2. Intracontinental -intercontinental rifting regime of intracontinental extension process (T3~E1) ; 3. Intracontinental orogenic regime which primary factor was the collision between India plate and Eurasian plate, caused by the combined action of India plate, Eurasian plate and Pacific-oceanic plate (E2~Q) .Three relatively isolated metallogenic subsystems formed in their own tectonic regimes. The main metallogenesis of island arc metallogenic subsystem (280Ma, U-Pb; 291.33+2.54Ma, Ar-Ar) is the contact metasomatic type Cu metallization and its possible metallogenesis is volcanic hydrothermal type Cu, Pb-Zn metallization; The metallogenesises of Intracontinental rifting metallogenic subsystem (143.2Ma, K-Ar; 157.41+ 1.20Ma, Ar-Ar) included the contact metasomatic type, sedimentation-exhalation type or volcanic hydrothermal solution type metallization, and the main metallogenesis is the contact metasomatic type Ag, Cu, Pb, Zn, Fe, Au, Ga etc metallogenesis caused by the intrusion of medium-acidic magma in Yanshan stage. The metallogenesis of Intracontinental orogenic subsystem (32.8-33.6Ma; 15.0-21.2Ma, ESR) mainly represents that the tectonic-magma-hydrotherm formed a series of Au, Ag polymetallic deposits or superposed and rebuilt some preexistent deposits. And the generalized homothetic composite action of metallogenic subsystems mentioned above formed the multiple-composite metallogenicsystem of the Jiangda tectonic belt.The typical ore deposits of Jiangda tectonic belt, such as Dingqinnong, Jiaduoling, Renda etc, are contact metasomatic type deposits formed intracontinental rifting stage, and the tectonic-magmatic-hydrotherm of intracontinental orogenic stage superposed and rebuilt some preexistent ore body. Their space distribution is controlled by composite intrusive rock belt of NE direction.Tectonic-lithogenic-mineralogenetic epoch and its geologic history evolution indicate that Intracontinental rifting stage (T3~E1) is the main metallogenic period of the Jiangda tectonic belt.Geological, Geophysical and geochemical research indicate that ore deposits space distribution present belt in NW direction and strip in NE direction is controlled by the lengthwise structure and transversal structure. In the fold-thrust belt, those ore deposits formed in pre-intracontinental-orogenic stage, such as Dingqinnong Ag-Cu polymetal ore deposit, have the character of one orebody beneath one, so it is optimistic to search new orebodys in deep.In north of whole three rivers tectonic belt include Jiangda tectonic belt, regional geochemical research indicate that its geochemical anomaly present the character of belt in NW direction and trip in NE direction, too. This is the geochemical response in earth's surface of deep-action. In nature, it is the consequence resulted by the terranes inserted as strips and blocks , regional transversal structure develope...