河南鲁山太华变质杂岩前寒武纪变质作用  

Metamorphic evolution of the Lushan terrane in the Precambrian Taihua complex,Henan Province

作　　者：卢俊生[1] 王国栋[1] 王浩[1] 陈泓旭[1] 吴春明[1] 

机构地区：[1]中国科学院大学地球科学学院,北京100049

出　　处：《岩石学报》2014年第10期3062-3074,共13页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41225007)资助

摘　　要：太华变质杂岩（＂太华群＂）出露于华北克拉通中部造山带南缘,包括自西北向东南依次出露的华山、洛宁、鲁山、舞钢等四个出露区。鲁山地区太华变质杂岩中的斜长角闪岩类,变质演化历史记录得相对最为全面,其中普遍保留了三个阶段的变质矿物组合。第一阶段变质矿物组合（M1）为进变质组合,以石榴子石变斑晶中的包裹体矿物组合（石英＋斜长石＋角闪石±单斜辉石±钛铁矿）为代表,形成于约710℃/7.8kbar的条件下。第二阶段变质矿物组合（M2）为变质高峰期组合,以石榴子石变斑晶和基质矿物组合（角闪石＋斜长石＋石英±单斜辉石±钛铁矿）为代表,形成于约730～810℃/8.1～11.7kbar的条件下。第三阶段的矿物组合为退变质组合,以环绕石榴子石变斑晶发育的后成合晶矿物组合（石英＋斜长石＋角闪石±单斜辉石±钛铁矿）为代表,形成的温度与压力条件约为730～740℃/3.5～5.7kbar。这些斜长角闪岩类记录了顺时针变质作用P-T轨迹,其中包含近等温降压的退变质过程,其中变质峰期变质条件达高角闪岩相到麻粒岩相过渡区。二次离子质谱（SIMS）探针锆石U-Pb定年表明,变质锆石年龄介于1.93～1.87Ga之间。结合其他学者发表的资料,推测华北中部造山带的中段和南段似乎在～1.95Ga即已开始了俯冲-碰撞的造山过程,而且该造山过程几乎延续了150Myr之久。Formerly term as the Taihua Group,the Taihua metamorphic complex locates at the southern terminal of the Trans-North China Orogen and consists of the Mts Huashan,Luoning,Lushan and Wugang terranes from the northwest to the southeast. The garnetbearing amphibolites from the Lushan terrane preserve three generations of metamorphic mineral assemblages,i. e.,the prograde,peak and retrograde metamorphic assemblages. The prograde metamorphic assemblages（ M1） are preserved as mineral inclusions in garnet porphyroblasts and are mainly composed of plagioclase,hornblende,quartz,with minor clinopyroxene,and were formed under metamorphic P-T conditions of 710℃ /7. 8kbar. The peak metamorphic assemblages（ M2） are represented by the relatively coarsegrained garnet porphyroblasts and hornblende,plagioclase,quartz or clinopyroxene in the matrix,and were formed under metamorphic P-T conditions of 730 ～ 810℃ /8. 1 ～ 11. 7kbar. The retrograde assemblages（ M3） occur as symplectitic minerals surrounding the garnet porphyroblasts,which were formed under P-T conditions of 730 ～ 740℃ /3. 5 ～ 5. 7kbar. Therefore,these amphibolites record clockwise P-T paths including isothermal decompression（ ITD） process. In-situ high resolution SIMS U-Pb dating of metamorphic zircons and metamorphic rims of zircons suggest that the metamorphism took place during 1. 93 ～ 1. 87 Ga. Combing previous dating retrieved from the middle to southern sections of the Trans-North China Orogen（ TNCO）,it is deciphered that the middle and southern sections of the TNCO was involved in a long-lived continental-continental collision,a period from ca. 1. 95 Ga to ca. ～ 1. 80 Ga ago.

关 键 词：华北克拉通中部造山带 鲁山 太华变质杂岩 斜长角闪岩 P-T-T轨迹 

分 类 号：P588.346[天文地球—岩石学] P597.3[天文地球—地质学]