Late Carboniferous Magmatic Activities in the Quanshenglinchang Area, the Great Hinggan Range: Constrains on the Timing of Amalgamation between Xing’an and Songnen Massifs
详细信息
- 责任者：Cui Fanghua (College of Earth Science ; Jilin University ; Changchun 130061 ; China) ; Zheng Changqing
- 刊名：Acta Geologica Sinica
- 出版年：2013
- 卷期：87(9)
- 关键词：花岗岩 ; granite ; 大兴安岭 ; Greater Hinggan Mountains
- 页码：p.1247-1263
- 图表：11 illus., 3 tables, 78 refs.
- 分类号：0801
- issnNo：ISSN0001-5717
- isbnNo：CN11-1951/P
摘要
Late Paleozoic granitoids without undergoing metamorphism in Quanshenglinchang area,Great Xing’ an Range mainly consist of medium biotite adamellite and medium-coarse biotite syenogranite.The study area lies in Xing’an Massif which is an eastern part of the Xing’an-Mongolian orogenic belt.Geochemical data suggest that these rocks are rich in SiO2（SiO2 =75.72%76.28%）,alkalis（Na2O+K2O=7.78% 8.89%）and are charactered by slightly peraluminous（Al2O3 =12.42%13.01%）and the low content of TiO2,Fe2O3,FeO,MnO,MgO,CaO,P2O5.They have high contents of normative quartz,albite,orthoclase and little corundum,zircon,apatite,magnetite,ilmenite,but do not contain alkaline melaminerals.These granitic rocks are slightly high in total REE and LREE contents,and show obvious fractionation of LREE from HREE with significant negative Eu anomalies.They are also characterized by enrichment in Rb,K,Pb,depletion in Ba,Sr,Eu,severe depletion in Nb,Ta,Ti（HFSE）and P.The features of A/CNK <1.1,normative corundum contents<1%,A/NK>1.0,negative correlation between P2O5 and SiO2,higher differentiation index（DI=92.4997.26）,lower saturation temperatures of zircon（730834℃）manifest that these granites belong to highly fractionated I-type.Zircons from these rocks exhibit hypautomorphic-automorphic crystal,clear oscillatory zoning,higher Th/U ratios（most in 0.361.35）,these characters indicate that they are magmatic in origin.The weighted average ages of zircon U-Pb isotope of these four samples are（322.2±1.2）Ma,（305.9±2.4）Ma,（301.3±2.6）Ma and（294.8±1.6）Ma,indicating that they formed during Late Carboniferous to early Permian.So,adamellite and syenogranite in the study area are considered as products of magmatic emplacement.The petrography,petrogeochemistry,chronology study and regional tectonic evolution reveal that these late Carboniferous intrusions in Quanshenglinchang area,Great Xing’an Range formed under a tectonic setting from lateorogenic to post-orogenic extension during the collision between Xing’an and Songnen Massifs,and the two massif had jointed at no later than the end of Early Carboniferous.
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