Three composite Jiangbei section Yushu area and mineralization of the orogenic

Title: Three composite Jiangbei section Yushu area and mineralization of the orogenicAuthor: Zhao-LinDegree awarded: Chinese Academy of Geological SciencesKeywords: Geology;; thrust structure;; porphyry-type deposits;; zircon LA-ICPMS U-Pb ages;; three Jiangbei sectionSummary:

Qinghai Yushu area located in the famous "three rivers" copper polymetallic mineralization with the extension part of the North, has great potential for mineralization. In this study, within the North Qiangtang block within the volcanic rocks and granite Yushu neodymium magnets suture zircon LA-ICP-MS U-Pb geochronology, geochemistry, combined with tectonic - magmatic activity and petrography, the late Paleozoic - Mesozoic tectonic units and tectonic evolution. In Yushu - Nangqian belt for Cenozoic tectonic evolution, deformation studies, based on the combination of copper and lead-zinc porphyry molybdenum mineralization dating, Jiangbei section of the Yushu area for three Cenozoic tectonic features and mineralization research.

Three Jiangbei section Yushu region has experienced two key geological processes of composite overlay, that the late Paleozoic - early Mesozoic subduction, collision orogeny and Cenozoic orogenic collision conversion process. Late Paleozoic - Early Mesozoic volcanic complex Yushu major rock band formed in the North Qiangtang blocks form the basis of the Permian - Triassic continental margin arc zone, north of the volcanic complex rock formation with the Bayan Har turbidites with, Cenozoic collision - Conversion to form orogenic stage large-scale strike-slip fault and thrust structure.

Yushu complex rock volcanic rock band has gone through strong compression and multi-level deformation, the widespread occurrence of shallow greenschist facies metamorphism to form a "fan" nappe tectonic units stacked on the cover on both sides. Developed with the major folds, lens, and a small fracture foliation structure, reflecting the collision process with extrusion. http://www.chinamagnets.biz/Neodymium/Ball-Neodymium-Magnets.php Yushu volcanic complex has been widely distributed rock band strongly deformed mafic dikes and granodioritic intrusions, which represents the collision with granite complex is widely distributed in Yushu volcanic belt and the Bayan Har turbidites band, The Qiangtang little development within the granodiorite rocks, the igneous rocks of the temporal and spatial distribution for the Jinsha River in Yushu region southward subduction of oceanic tectonic units of the division and provide good evidence.

Permian subduction orogeny in the North Qiangtang block the formation of sodium on Gongma - sub-margin arc volcanic rocks with music, volcanic zircon LA-ICPMSU-Pb age of 275.4 Ma, 273.3Ma, geochemical features suggest that enrichment ion lithophile elements (LILE), depleted in high field strength elements (HFSE), has the characteristics of island arc volcanic rocks, volcanic rocks with high ~ (176) Hf / ~ (177) Hf and εHf (t) values, indicating magma source District should have a loss on the Bay asthenosphere mantle join.

Triassic volcanic rocks and the formation of active continental margin magmatic arc granite. East Mozart caught mine volcanic zircon LA-ICPMS U-Pb age of 236.6 ± 1.9Ma and 238.3 ± 4.0Ma, volcanic rocks and zircon REE, Hf isotopes show the characteristics of a continental margin arc volcanic rocks. Yushu arc magma intruded into the volcanic complex of granite rocks, two biotite granite zircon U-Pb ages of 235.2 ± 1.2Ma and 228.7 ± 1.2Ma, in addition to the individual, the samples generally silicon and alkali-rich components, poor P_2O_5 and TiO_2 and other components, the overall calc-alkaline series, the three major elements of granite samples with good correlation characteristics, shows a clear crystal fractionation, sample trace elements and REE distribution patterns are similar to magmatic arc granite rocks from diorite quartz diorite → → → granodiorite, biotite granite, more and more enriched in light rare earth rare earth elements present, more and more loss of heavy rare earth, rare earth fractionation characteristics of more and more obvious that the The granite is a product of the Jinsha subduction stage.

Permian and Triassic active continental margin arc volcanic belt on the continental margin to reflect the occurrence reduce the Jinsha oceanic crust, ocean - land conversion and crustal tectonic northward proliferation process. However, the Late Paleozoic - Early Mesozoic orogeny in the third section of the Yushu area Jiangbei and not a lot of development similar to the Sanjiang tectonic belt - southern section of the back-arc spreading (rift) environment "bimodal" combination of rock, there is no large-scale development collisional stage of the volcanic rocks and the role of post-collisional extension, may be Late Paleozoic - Early Mesozoic mineralization adversely.

Cenozoic collision - conversion in three orogenic deformation Jiangbei section the formation of two styles that strike-slip tensile and compression together, strike-slip extension in the context of the formation of strike-slip fault, strike-slip pull-apart basin and rich alkaline intrusive rocks, potassium - ultra-potassic volcanic rocks, squeezed together to form the context of large-scale thrust nappe system, thrust nappe system in the thrust direction from south to north into the root zone, the zone and forward zone , respectively, each with between the main thrust apart. Two tectonic deformation pattern corresponding to the study area, the formation of two ore-forming system, the late collision stage strike-slip fault-controlled porphyry mineralization system and thrust structural control of hydrothermal mineralization system, the former on the formation of sodium Gongma porphyry molybdenum copper deposit, the mineralization age of 40.86 ± 0.85Ma (Re-Os method), and showed the Sanjiang region from north to south porphyry emplacement and mineralization age gradually become a new trend; thrust cover structural control of hydrothermal ore-forming system to form the East Mozart arrested and Mohailaheng lead-zinc deposits, deposits formed in the thrust-nappe belt striker, prolific ore body in the imbricate thrust fault on the ( below) or recoil plate fracture zone near the fault, mineralization age of 35.03 ± 0.89Ma and 34.0 ± 1.1Ma (Rb-Sr method).Degree Year: 2009