吉林

发布时间：2018-02-01 23:10

本文关键词： 吉林省二叠纪古亚洲洋锆石U-Pb定年地球化学　出处：《地学前缘》2017年02期 　论文类型：期刊论文

【摘要】：对出露于吉林省"大黑山条垒带"、行政区辖属伊通县发展乡一带的"大黑山火山岩"-安山质凝灰熔岩、片理化流纹岩分别采样并挑选锆石,经LA-ICP-MS定年,查明安山质凝灰熔岩74颗锆石的~(206)Pb/~(238)U年龄介于1 873~240 Ma,其中~(206)Pb/~(238)U年龄值介于317~240 Ma的69粒锆石均显示出岩浆成因特征,表明研究区自晚石炭世晚期便存在火山事件,火山喷发活动于早、中二叠世发展至峰期,该火山岩形成于晚石炭世晚期至晚二叠世,并于早、中三叠世遭受了岩浆作用;古元古代、中元古代、中泥盆世及早石炭世锆石具碎屑锆石特征,可能为被捕获的古老锆石。片理化流纹岩38粒锆石的~(206)Pb/~(238)U年龄介于307~240 Ma,且均显示出岩浆成因特征,表明该火山岩形成于早二叠世早期至晚二叠世,并遭受了印支期岩浆作用。所研究的"大黑山火山岩",前人多认为其与同地区桃山组地层时代相当,为早志留世或中志留世,但本文所获该火山岩的年龄表明二者年龄时限完全不同,故大黑山火山岩与桃山组地层应完全要剥离开来,分属不同时代残留的构造岩片。上述火山岩富集轻稀土元素和大离子亲石元素,亏损高场强元素,表现出类似岛弧或活动大陆边缘火山岩的特征;在Th-Ta-Hf/3三角图和Nb/Th-Zr/Nb和Nb/Yb-Th/Yb构造环境判别图中投点在火山弧火山岩、活动大陆边缘附近,表明该火山岩可能与当时古亚洲洋板块向松嫩地块俯冲所形成的火山弧有关。
[Abstract]:For the "Daheishan volcanic rock"-Anshan tuffaceous lava, which is exposed to the "Dasheishan Horst Belt" in Jilin Province and belongs to the Development Township of Yitong County, zircon is sampled and selected from the sheet physicochemical rhyolite. According to the LA-ICP-MS dating, 74 zircon zircons from the Anshan tuff lava are found to have an age range of 1873 ~ 240 Ma. Among them, 69 zircon samples with a Pb / P ~ (238) U age of 317 ~ 240 Ma all show magmatic genetic characteristics, indicating that volcanic events have existed in the study area since the late late Carboniferous. The volcanic eruption occurred in the early, middle Permian to the peak period. The volcanic rock was formed from the late Carboniferous to the late Permian, and suffered from magmatism in the early and middle Triassic. Paleoproterozoic, Mesoproterozoic, Middle Devonian and early Carboniferous zircon have the characteristics of clastic zircon. Probably an ancient zircon captured. 38 zircons from the schistatic rhyolite show magmatic characteristics. The age of 38 zircons is between 307 and 240 Ma. It shows that the volcanic rock was formed from the early Permian to the late Permian and suffered from the Indosinian magmatism. For the early Silurian or the Middle Silurian, the age of the volcanic rock obtained in this paper indicates that the ages of the two volcanic rocks are completely different, so the strata of Dashan volcanic rock and Taoshan formation should be separated completely. These volcanic rocks are enriched in light rare earth elements and large ion lithophile elements, and depleted in high field strength elements, showing characteristics similar to island arc or active continental margin volcanic rocks. In the Th-Ta-Hf/3 triangle diagram and the Nb/Th-Zr/Nb and Nb/Yb-Th/Yb tectonic environment discriminant diagram, the input point is near the volcanic arc volcanic rock, active continental margin. It is suggested that the volcanic rock may be related to the volcanic arc formed by the subduction of the paleo-Asian ocean plate to the Songnen block at that time.
【作者单位】：山东科技大学山东省沉积成矿作用与沉积矿产重点实验室;国土资源部沉积盆地与油气资源重点实验室;
【基金】：国家自然科学基金项目(41372108) 高等学校博士学科点专项科研基金项目(20133718130001) 山东科技大学矿山灾害预防控制省部共建国家重点实验室培育基地项目(MDPC2013KF18);山东科技大学科研创新团队支持计划项目(2015TDJH101)
【分类号】：P534.4;P542
【正文快照】： 20世纪80年代以来,国内外越来越多的学者以“板块构造”的观点求索东北地区的大地构造属性和构造演化。Зоненшайн等[1]认为,古特提斯洋北支蛇绿岩沿塔里木盆地南缘至北山,经蒙古国南缘文在“大黑山条垒带”首次确认晚二叠世弧火山岩的存在,将为该区当时洋陆分布的格

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