扬子北缘晚古元古代A型花岗质岩: Columbia超大陆裂解的证据  

Late Paleoproterozoic A-type granitic rocks in the northern Yangtze block:evidence for breakup of the Columbia supercontinent

作　　者：黄明达 崔晓庄[2,3] 程爱国 任光明[2] 何虎庄 陈风霖 张恒利 张建强 任飞[2] HUANG Mingda;CUI Xiaozhuang;CHENG Aiguo;REN Guangming;HE Huzhuang;CHEN Fenglin;ZHANG Hengli;ZHANG Jianqiang;REN Fei(General Prospecting Institute , China National Administration o f Coal Geology , Beijing, 100039;Chengdu Center of China Geological Survey ,Chengdu 610081;Chengdu University of Technology ,Chengdu,610059;Tarim Oilfield Company of PetroChina , Korla, Xinjiang, 841000)

机构地区：[1]中国煤炭地质总局勘查研究总院,北京100039 [2]中国地质调查局成都地质调查中心,成都610081 [3]成都理工大学沉积地质研究院,成都610059 [4]中国石油塔里木油田分公司,新疆库尔勒841000

出　　处：《地质学报》2019年第3期565-584,共20页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号41872120;41502114);中国地质调查局项目(编号DD20160017;DD20160187;DD20179386)联合资助的成果

摘　　要：为约束扬子陆块晚古元古代构造演化历史,以华山观岩体的钾长花岗岩和二长花岗岩为研究对象,开展地球化学、年代学、全岩Nd同位素及锆石Hf同位素分析。锆石U-Pb定年结果显示钾长花岗岩和二长花岗岩的结晶年龄分别为1860±12 Ma(MSWD=0.69)和1832±14 Ma(MSWD=0.48)。两类岩石都显示铝质A型花岗岩的地球化学特征,一致的ε_(Hf)(t)值(-10.9～-13.8)及其二阶段模式年龄(2962～3183 Ma),揭示其由同一套太古宙的地壳部分熔融形成。综合已有ε_(Hf)(t)值资料,表明扬子陆块广泛存在两套太古宙长英质地壳(3.0～3.5 Ga; 3.5～3.9 Ga),为华山观两类花岗岩的岩浆形成提供了物源。华山观岩体两类花岗岩的锆石饱和温度揭示源岩位于较深的地壳,且二长花岗岩的形成有更多热源的参与。结合扬子陆块同期(～1.85Ga)A型花岗岩的地球化学数据,认为华山观钾长花岗岩具有后碰撞A_2型花岗岩的特征,形成于后碰撞伸展环境,而华山观二长花岗岩具有A_1型花岗岩的地球化学特征,暗示造山后伸展到陆内裂谷过渡的构造背景,可能与Columbia超大陆裂解有关。In order to constrain the Late Paleoproterozoic tectonic evolution of the Yangtze Block, this paper reported the geochemical, geochronological, whole-rock Nd isotopes and zircon Hf isotope analyses of the K-feldspar granites and monzogranites from the Huashanguan complex. U-Pb dating of magmatic zircons from K-feldspar granites and monzogranites yielded ages of 1860±12 Ma and 1832±14 Ma respectively, representing the age of their formation. The two types of granitoid are geochemically characterized by aluminous A-type granite. The consistent εHf(t) values(-10.9^-13.8) and TDM2(2962~3183 Ma) indicate that the K-feldspar granites and monzogranites in the Huashanguan complex were formed by partly melting of the single Archean crust. The previous εHf(t) results also indicate that there two widely-distributed Archean felsic crusts(3.0~3.5 Ga;3.5~3.9 Ga) in the Yangze Block provided material source for the magmatic evolution of the two types of granitoid. Zircons saturation temperatures of two types of the granite in Huashanguan reveal that the samples should source from much deep crust and monzogranites formed with more heat sources involved. Combined geochemical evidence of coeval A-type granite in the Yangtze block(~1.85 Ga), it can be concluded that the K-feldspar granites in Hushanguan complex and coeval A-type granite have features of post-collisional granite(A2-type and formed in a post-collisional setting. The monzogranites show the geochamical characteristic of A1 type granite, indicating a tectonic environment from post-collision to intraplate rift. The two magmatic events may be related to the breakup of Columbia supercontinent.

关 键 词：扬子陆块 铝质A型花岗岩 造山后伸展 陆内裂谷:Columbia超大陆 

分 类 号：P588.121[天文地球—岩石学]