Metallogeny Of Copper Ores From The Lancangjiang Metallogenic Belt In Western Yunnan

The Lancangjiang metallogenic belt in Western Yunnan is an important magmatic, metamorphic and tectonic mobile zone of Southwestern China, whose geotectonic location is very unique. It is characterized by complex geological structures, perfectly developed strata, frequent magmatic activities, various degrees of metamorphism, rich ore resources and lots of metal deposits, thus formed a centralized zone of mineralization and also constituted one of the important metallogenic belts of noble and nonferrous metal deposits. That is why the researching on geology for this belt is of great significance.Geotectonically, the belt lies in the junction of Gondwana paleao-super梒rustobody with Laurasia paleo-super-crustobody, which can be subdivided into three segments:(1) The Lanping -Simao area, which includes the Cangshan - Ailaoshan Paleoproterozoic continent-genetic metamorphic basement, the Anding-Tengtiaojiang Paleozoic ophiolitic melange belt, the Weixi-LUchun Indosinian rift valley, the Lanping-Simao Mesozoic marginal collapse belt, the Lancangjiang Indosinian volcanic arc and the Lancangjiang converging-connection belt.(2) The Changning-Menglian area, which consists of the Lancang-Ximeng Mesoproterozic, Neoproterozic and Early Paleozoic metamorphic basement stratum, the Changning-Menglian Late Paleozoic continental marginal rift system and Kejie-Nandinghe converging-connection belt.(3) The Baoshan area, which outcrops the Chongshan Mesoproterozic, Neoproterozic and Early Paleozoic metamorphic basement, Baoshan continental shelf rift and Nujiang converging-connection belt .As a part of the transitional domain of South Asia crustobody, Central Asia crustobody and East Asia crustobody, the zone has undergone the process of splitting and amalgamation time after time in its evolution history. The tectonic evolution history in this region is summarized as follows:(1) Late Devonian-Early Triassic stage: With the fragmenting of Early Paleozoic super ?crustobodies, the zone was split and formed gap geosynclinal region called the Lancangjiang Transitional Field (LTF) which is an important and special advantage of mineralization in this region during Late Devonian-Early Carboniferous Epoch. The Carboniferous-Permianperiod was the main period of splitting, and in which there existed rock梐ssemblage belts of tholeiitic series, calc梐lkaline series and alkali basaltic series. At the top of the Late Permian series, the neritic or paralic pyroclastic sediments were formed on the top of volcanic arc. For the sediments of lower Triassic series doesn't exist in whole area, the Lancangjiang paleo梘eosyncline was closed during the Late Permian桬arly Triassic Epoch.(2) Middle桳ate Triassic stage.- When the process of splitting and amalgamation of the Lancangjiang tectonic zone took place again in this period, volcanic rocks belt was formed and the three crustosections converged completely in the end. At the same time, the evolutionary process of the three crustosections as a whole was beginning in this region.(3) Late Triassic final stage to this day: After the transient platform stage, the whole area turned into diwa stage at the end of the Late Triassic Epoch. With the continuous equilibrium sedimentation of the whole area controlled by block faulting, this area became a sag basin and the sag lasted to the Himalayan movement period. At the end of Tertiary, as South Asia crustobody was sutured to Eurasia super梒rustobody, lots of folds and large reversed nappes in all strata was formed in this area.Influenced by its tectonic evolution, copper梡olymetal ores in the belt which are broadly limited by the LTF tectono梞etallogenesis are characterized by multi-stage and multi-series in the same sites. In its three main evolution stages, there are different metallogenetic series in this area.(1) During Late Devonian桬arly Triassic Epoch, the alkali梑asalt梙osted deposits were formed in the early splitting period, and the ophiolite series梙osted deposits including the spilite梜eratophyre series梙osted deposits formed in the...