岩石矿物学杂志2012，Vol.31Issue(3)：323-334,12.
内蒙古东乌旗狠麦温都尔花岗岩SHRIMP锆石U-Pb年龄及其地质意义
SHRIMP zircon U-Pb dating of granites in Mahonondor area, East Ujimqin Banner, Inner Mongolia
摘要
Abstract
The Mahonondor granites, located in East Ujimqin Banner of Inner Mongolia, are predominated by monzogranite and syenogranite. SHRIMP zircon U-Pb dating shows that the crystallization age of the monzo-granite is 307.0 ± 1.9 Ma and that of the syenogranite is 299.7 ± 5.3 Ma. The ages which are between the late Carboniferous and early Permian are consistent with the late Paleozoic magmatic activity age. Geochemical researches indicate that the granite from Mahonondor area in the East Ujimqin Banner of Inner Mongolia is rich in silica (SiQ2 = 65.65%～71.86%), alkali (K2O +Na2O = 9.59%～9.90%) and K (K2O/Na2O= 1.00% ～ 1.73 %), suggesting a typical high-K calc-alkaline to shoshonitic series with the metalummous feature (A/CNK = 0.96～1.04). The rocks are poor in rare earth elements (SREE = 82.60 × 10-6～ 157.70 × 10-6), enriched in LREE [(La/Yb)N = 4.13～15.37] and LILEs (Rb, Th, K), and depleted in HFSE, especially Nb, Ta, Sr, P and Ti. Similar REE distribution patterns indicate that the Mahonondor granites have the same magma source. The SEu values vary from 0.44 to 0.87, with most rocks having moderate negative Eu anomalies. In addition, massive structure and miarolitic structure point to post-collisional granites. In a word, these characteristics suggest that these high-K calc-alkaline granites in the Mahonondor area were emplaced during post-collisional conversion from compression to extension, and were derived from fractional crystallization of medium-K calc-alkaline diorite-porphyrite, causing collision between the Sino-Korean and Siberian plates during late Devonian to early Carboniferous period. It is shown that the conversion time of the late Paleozoic orogenic process in East Ujimqin area was from 320.1 ± 7.2 Ma to 307 ± 1.9 Ma, the period 286～276 Ma was the developmental stage of post-collisional alkali granites, and Hegenshan oceanic basin had disappeared before 320.1 ±7.2 Ma. The above results provide new constraints on Mongolia Orogenic Belt tectonic-magmatic evolution in Late Paleozoic and closure of the Paleo-Asian Ocean.关键词
东乌旗/高钾钙碱性花岗岩/后碰撞/SHRIMP锆石U-Pb年龄Key words
East Ujimqin Banner/ high-K calc-alkaline granites/ post collision/ SHRIMP U-Pb dating分类
天文与地球科学引用本文复制引用
程银行,滕学建,辛后田,杨俊泉,冀世平,张永,李艳锋..内蒙古东乌旗狠麦温都尔花岗岩SHRIMP锆石U-Pb年龄及其地质意义[J].岩石矿物学杂志,2012,31(3):323-334,12.基金项目
国家地质大调查项目(矿调[2005]11-5,1212011121079) （矿调[2005]11-5,1212011121079）
