地质论评2019，Vol.65Issue(1)：221-231,11.DOI:10.16509/j.georeview.2019.01.015
东准噶尔老爷庙地区碱性花岗岩锆石U-Pb定年、地球化学及其地质意义
Zircon U-Pb Dating, Geochemical Characteristics of Alkali-granites in Laoyemiao Area, Eastern Junggar, and Geological Significance
摘要
Abstract
Objectives: Laoyemiao area is located in east of East Junggar, known as the important tectonic metallogenic belt of the Central Asian Orogenic Belt ( CAOB) . Through high-precision zircon U-Pb dating and comprehensive research on rock geochemistry, combined with regional comparison, the diagenetic age was determined and its formation environment was discussed to provide chronology and petro-geochemical constraints for the study of Late Paleozoic tectonic magmatism.Methods: The full analysis of the rock was tested in the Aussie Minerals Laboratory in Guangzhou. After the sample was crushed, shrunk and ground to 200 mesh, the content of rare earth elements was determined by MEMS81 fusion inductively coupled plasma mass spectrometry. ME-XRF26 X fluorescence spectrometer was used for precise analysis. Determination of iron oxide by the main trace element of rock and Fe-VOL05 titration.Zircon single minerals were selected in the laboratory of the Institute of Regional Geology and Mineral Resources Research of Hebei Province, and the target, CL photographing, transflective photography, zircon dating and data were carried out in the State Key Laboratory of Mineral Deposits Research Mechanism of Endogenous Metal Deposits, Nanjing University. Correction. The zircon U-Pb test was carried out on an Agilient 7500 a ICP-MS connected by a 193 nm laser sampling system. The laser ablation beam spot diameter was 32 μm and the frequency was 6 Hz. He gas was used as the carrier gas for the ablation material, and then mixed with the Ar gas. Analyze.The isotope ratios obtained by the experiment were processed by the GLITTER program and subjected to ordinary lead calibration. The test results are shown in Table 2. The age harmonic curve and the weighted average calculation were processed using Isoplot ( 3.0) software.Results: Laoyemiao alkali granites are characterized by high Si O2 ( 63.58％ ～69.92％) , high alkaline ( Na2 O+K2 O: 9.38％ ～ 9.81％) , low CaO ( 0.44％ ～ 2. 47％) and low Ti O2 ( 0.52％ ～ 0.97％) , Similar to typical A-type granites, which genesis type belongs to the A2-type granites and produced in the post-orogenic environment. The alkali granites are enriched Rb、Ba、K、Th、Zr and relatively depleted in P、Ti、Nb、Ta. Obvious enrichment light rare earth elements ( LREE/HREE = 7. 62 ～ 8. 31) , the internal fractionation of light rare earth elements is relatively strong, but weak in heavy rare earth elements, and lack in Eu anomaly ( δEu = 0.52 ～ 0.91) . Zircon temperature saturation temperature of 819 ～ 890℃, belonging to high-temperature granite, moderate pressure. The zircon U-Pb age of LA-ICP-MS shows that its crystallographic age is two phases, which are 297.0±6.5 Ma and 310.0±2.0 Ma, respectively, indicating that the age of its formation is Late Carboniferous.Conclusions: Laoyemiao area was tiled into the Siberian plate at the end of the Late Carboniferous period ( 297.0±6.5) Ma and entered the transitional period of post-orogenic conversion into the plate.The lateral growth of the crust in the area was ended, but the area was still vertically proliferated due to the intrusion of a large amount of mantle-derived magma to the lower crust.关键词
东准噶尔/碱性花岗岩/后造山环境/锆石U-Pb定年/岩石地球化学/晚石炭—早二叠世Key words
east Junggar/alkali granite/post-orogenic environment/zircon U-Pb dating/petrogeochemistry/Late Carboniferous—Early Permian引用本文复制引用
熊双才,张征峰,李广,刘润泽,华叙登,赵富庄,周鹏飞,李关禄..东准噶尔老爷庙地区碱性花岗岩锆石U-Pb定年、地球化学及其地质意义[J].地质论评,2019,65(1):221-231,11.基金项目
中央返还新疆两权价款"新疆巴里坤县1:50000 L46E020016、L46E020017、L46E021015、L46E021016、L46E022015、L46E022016六幅区域地质调查"(编号:T15-1-LQ01)的成果 （编号:T15-1-LQ01）
