摘要
对满都拉地区蛇绿混杂岩的基质碎屑岩进行了锆石U-Pb年龄及Lu-Hf同位素研究。岩屑杂砂岩(D18003RZ1)锆石多具岩浆成因特征,U-Pb年龄分布于272~2302 Ma之间,有282 Ma和442.8 Ma两个峰值年龄;431~456 Ma锆石的^(176)Hf/^(177)Hf值为0.282661~0.282797,ε_(Hf)(t)值为6.4~10.7,T_(DM2)介于801~1155 Ma之间;272~286 Ma锆石的^(176)Hf/^(177)Hf值为0.282554~0.282768,ε_(Hf)(t)值介于-1.5~5.9之间,T_(DM2)介于1069~1575 Ma之间。含粉砂绢云母硅质板岩(DC01TW1)锆石年龄分布在260~2185 Ma之间,其锆石有岩浆成因,也有变质成因,主要峰值年龄为270 Ma,次为1600 Ma和1850 Ma;263~293 Ma锆石的^(176)Hf/^(177)Hf值为0.282434~0.282805,ε_(Hf)(t)值为-6.0~7.1,T_(DM2)介于930~1894 Ma之间。杂砂岩以古生代碎屑锆石为主,少量古中元古代锆石,反映其物源以兴蒙造山带为主,而绢云母硅质板岩以晚古生代和古中元古代为主,反映其物源可能以兴蒙造山带和华北陆块并重。结合2种岩性的岩石组成、锆石年龄分布及物源分析,杂砂岩可能形成时代略早,且靠近岛弧,而绢云母硅质板岩形成时代稍晚,其环境更靠近陆块。满都拉地区这套碎屑岩的形成时代可能为晚二叠世,且可能不晚于256 Ma,形成于俯冲向碰撞转变的构造背景,进一步限定内蒙古中部的古亚洲洋在晚二叠世依然存在,其演化可能一直延续到晚二叠世末。
Zircon U-Pb geochronology and Lu-Hf isotope of matrix clastic rocks in the Mandula ophiolitic mélange were studied in this paper.Most of the detrital zircons in greywacks(D18003RZ1)are magmatic crystallization origin.The zircon U-Pb ages range from 272 Ma to 2302 Ma with two peak ages of 282 Ma and 442.8 Ma.The^(176)Hf/^(177)Hf ratios of zircons from 431 Ma to 456 Ma range from 0.282661 to 0.282797.The values ofε_(Hf)(t)range from 6.4 to 10.7,and T_(DM2)range from 801 Ma to 1155 Ma.The zircon^(176)Hf/^(177)Hf ratios of 272~286 Ma range from 0.282554 to 0.282768.The values ofε_(Hf)(t)is between-1.5 and 5.9,and T_(DM2)is between 1069 Ma and 1575 Ma.The zircon ages of the silty sericite bearing siliceous slate(DC01TW1)range from 260 Ma to 2185 Ma.The zircons are magmatic origin and metamorphic origin.The main peak age is 270 Ma,and the secondary peaks are 1600 Ma and 1850 Ma.The zircon^(176)Hf/^(177)Hf ratios of 263~293 Ma range from 0.282434 to 0.282805.The values ofε_(Hf)(t)range from-6.0 to 7.1,and T_(DM2)range from 930 Ma to 1894 Ma.The detrital zircons in greywack reflect that the provenance is mainly Xingmeng orogenic belt.Siliceous slate are mainly Late Paleozoic detrital zircons and Paleo-Meso Proterozoic detrital zircons,that show the provenance area might be the Xingmeng orogenic belt and the North China block.Combined with the rock composition,zircon age distribution and provenance analysis of the two lithology,the greywacks may have formed a little earlier and close to the island arc,while the sericite siliceous slate formed a little later and its environment is closer to the continental block.The clastic rocks in Mandula area might have formed in the Late Permian and not be later than 256 Ma.They might have formed in the transformation background from subduction to collision,which further limited that the Paleo Asian Ocean in central Inner Mongolia still existed in the Late Permian,and its evolution might have continued to the end of the Late Permian.
作者
许立权
肖剑伟
张玉清
呼日乐
张婷婷
马嘉骏
XU Liquan;XIAO Jianwei;ZHANG Yuqin;HU Rile;ZHANG Tingting;MA Jiajun(Inner Mongolia Key Laboratory of Magmatic Mineralization and Ore-Prospecting/Geological Survey Institute of Inner Mongolia,Hohhot 010020,Inner Mongolia,China)
出处
《地质通报》
CAS
CSCD
北大核心
2023年第2期223-238,共16页
Geological Bulletin of China
基金
内蒙古自治区自然科学基金项目《内蒙古索伦山蛇绿混杂岩带物质组成与构造背景研究》(编号:2017MS0412)
中国地质调查局项目《中国区域地质志·内蒙古志》(编号:121201130132001)
内蒙古党委组织部项目《内蒙古重要成矿带成矿规律及找矿预测研究》创新人才团队(2015)。