Eastern Tibet River Tectonic Zone Evolution And Mineralization

Jiangda tectonic zone is an important metallogenic zone in the area of SanJiang.It is limited to some original concepts from scholar's understanding about Jiangda tectonic zone in a long time. The primary acquaintance with the Jiangda tectonic zone is that the collision between the Yangzi plate and the Changdu terrain with the close of JinSha river formes volcanic magma zone or volcanic island arc zone, pericontinental arc-island arc zone, and it came into the intracontinent convergent period from the collision of fold belt in middle Triassic Epoch, and overprinted the fold shrink and sliding in the Himalayan period.The viewpoints above-mentioned reflect some facts about the tectonic zone of Jiangda, but there are some inconsistency with much geological truth: (1)By consulting lots of the geological profile data and the reports of regional geological survey and investigating, we find the fact that the basin of Changdu was not being the regional discordance from Late Triassic stratum to Palaeocene stratum, the sedimentary facies were not being the orogenetic synchronous molasses formation in the both sides of the Changdu basin, and the faults not being the characters of press and sink. (2) Detailed comparing the sedimentary facies and sedimentary thickness of the Jiangda tectonic zone with the adjacent area of Changdu from Late Triassic epoch to Cretaceous, which discovered that the ancient geomorphy was basin-mountain type since Late Triassic epoch. (3)In the Late Triassic epoch, the volcano-graben zone of the Jiangda tectonic zone, not only had huge sedimentary thickness, but also appeared the ocean ridge and alike ocean ridge tholeiite, and so on.By all appearances, these viewpoints had some problems, which not only gone against resource-survey and the estimate of resource potential, but also gone against scientific understanding of the whole Sanjiang tectonic zone.Guided by terrain-plate tectonics theory and the ore-forming tectonics and supported by the research projects of "The evaluation of the northern Jiangda volcano-island arc Cu-Ag polymetallic deposits in Easter Tibet" and "The synthesis study of the metallogenic rule and ore-finding aspect in the northern of the southwest Sanjiang Area" etc, author fully studied the tectonic evolvement and couple relation between tectonic and ore-forming in Jiangda tectonic zone according to different tectonic system having different ore-forming action. Based on the fully absorbing data of predecessor and investigating, analyzing sedimentary construct ,ancient geography, rock geochemistry, tectonic rock-stratum, different scale tectonic parse, ancienttectonic stress field, tectonic-diagenism-metallogenetic dating and so on , some new understanding were achieved as follows:(1) The Jiada tectonic zone was very important as Caledon young crust terrain eastern margin caused by the development of the Jiashajiang-Ainaoshan ocean in Palaeozonic.(2) The rifting which formed the Jiashajiang-Ainaoshan ocean started in Devonian. In Early Carbonic the ocean basin come into being. And partial ocean crust started to dive under into Changdu Land Block in the later Carbonic. Full-scale ocean-land dive occurred in early Permian last stage .The ocean basin closed in the middle Trias last stage which led to the seaming of Changdu Land Block and Zhongzan Land Block. But collision mountain-building force was not great. (To some extent, because the Zhongzan Land Block was limit in scale, regional stretch system didn't happen ultimately change.)(3) The Jiada tectonic zone undergone passive continental margin in Neopaleozoic, and inland central valley from Late Triassic epoch to Kainozoin era early stage, and inland dive-nappe-fault-strike slip etc multistage development.(4) The Jiada tectonic zone inland central valley undergone the volcano-graben in Late Triassic epoch-Early Jurassic, inland depressed in Middle Jurassic-Later Cretaceous, fault-strike slip moat-horst in Palaeocene-Middle Eccene, valley closed moutain-building in Eccene-Oligocene, Molasse basin development stage and so on.(5) From the relations of stratum contact, deformation fashion and deformative stress field, similar/rear orogenetic molasse building epoch, regional deformation, metamorphism and mineralogenetic chronology, magma action feature etc, the intensity of collasion orogenic in middle Triassic Epoch at JiangDa tectonic zone is not strong. The main deformations deteriorate in Himalayan period since late Triassic Epoch that is Himalaya fold orogen and it is with the feature of thrust-nappe-slide.(6) It constitutes the four different distinctive metallogenesis system because Jiangda tectonic zone's metallogenesis happens across the different system of four evolutionary processes. Passive epicontinental metallogenic system only be seen with some gold ore traces in metamorphic terrain of JiangDa tectonic zone. The metallogenesis of active epicontinental (Magma Arc) metallogenic system (280Ma, U-Pb; 291.33 ± 2.54Ma, Ar-Ar) mainly represents the type of contact replacement Cu mineralized and maybe exit the type of volcano hydrotherm Cu, Pb-Zn mineralized; The metallogenesis of intracontinental rift mineralogenetic is Fe, Cu, Pb, Zn, Ag, Au, Ca etc metallogenesis of contact replacement pattern caused by the invasion of acid magma in Yanshanian and SEDEX type Fe,Pb,Zn,Ag metallogenesis in the stage of late Triassic Epoch volcano graben; The metallogenesis of intracontinental orogenic metallogenic system is mainly composed of three parts: (D intensive thrust-nappe allocating the ore deposit again; ? structure-magma-hydrothem activating and re-enriching the phantom ore deposit again; G> structure-magma-hydrothem shaping new ore family and new ore deposit on adaptable position.(7) The four metallogenesis metallogenesis systemes mentioned above happen in succession in the same tectonic zone. It appears the features of succession, development and modification certainly which will result in the low display of passive...