山东莱芜盆地火山碎屑岩锆石U-Pb年代学研究  

ZIRCON U-PB GEOCHRONOLOGY AND TRACE ELEMENT GEOCHEMISTY OF VOLCANIC CLASTIC TUFF IN THE LAIWU BASIN,SHANDONG PROVINCE

作　　者：宁振国[1,2] 孟凡巍[3,4] 刘吉强[1,5] 李聪颖[4] 杨恩秀[2] 胡永斌[1,6] 

机构地区：[1]中国科学院广州地球化学研究所矿物学与成矿学重点实验室,广东广州510640 [2]山东省地质调查院,山东济南250013 [3]现代古生物学与地层学国家重点实验室,中国科学院南京地质古生物研究所,江苏南京210008 [4]同位素地球化学国家重点实验室,中国科学院广州地球化学研究所,广东广州510640 [5]国家海洋局海底科学重点实验室,国家海洋局第二海洋研究所,浙江杭州310012 [6]中国科学院大学,北京100049

出　　处：《地层学杂志》2015年第1期108-115,共8页Journal of Stratigraphy

基　　金：973项目(No.2011CB403007);国家自然科学基金(No.41103012;No.41173051);中国博士后科学基金(No.2012M511842)联合资助

摘　　要：山东山旺盆地的山旺组硅藻土沉积，素以保存化石精美而被称为地质历史的“万卷书”，最近在莱芜盆地也发现了相似的硅藻土沉积和化石保存。山旺盆地的山旺组上下都为玄武岩，最新的^40Ar/^39Ar定年结果山旺组下部玄武岩为21.0 Ma,而上部玄武岩为17.3 Ma左右；夹在山旺组中的玄武岩在17～18 Ma左右，因此判断山旺组的年龄大致为17-21 Ma。为了判断莱芜盆地的硅藻土沉积是否与山旺盆地的山旺组沉积于同一时代，对山东莱芜盆地中玄武质火山凝灰岩中的锆石进行了U-Pb定年和微量元素测定，Th/U比值为0.68～1.37，表明为岩浆成因锆石。定年结果表明莱芜盆地中玄武质火山岩的最后一次喷发时间在14.5±0.3 Ma，与山旺盆地山旺组相比更加年轻。在山东新近纪的断裂盆地中，硅藻土沉积保存的化石在相似的构造背景下，可以在不同时代的盆地中产生，而莱芜盆地记录了更为年轻的硅藻土保存的化石。The kieselguhr sediments from the Shanwang Formation in the Shanwang basin, western Shandong, are known as a geological book because of their preservation of beautiful fossils. Similar ieselguhr sediments with well-preserved fossils have been recently discovered from the Laiwu basin. In order to determine whether the kieselguhr sediments from Laiwu and Shanwang basins can be correlated, we carried out U-Pb dating and trace element analysis of zircons isolated from basaltic volcanic turfs. The zircons from the Laiwu Basin have a Th/U ratio of 0.68-1.37, suggesting a magmatic origin, and they constrain the most recent basaltic magmatic event to be 14.54-0.3 Ma. In contrast, basalts below and above the Shanwang Formation give^40 Ar/^39 Ar ages of 21.0 Ma and 17. 3 Ma, respectively. Additionally, basahs within the Shanwang Formation were emplaced at ca. 17Ma, indicating that Shanwang Formation was deposited ca. 17 Ma. It can be inferred that fossiliferous kieselguhr sediments can be preserved in basins of diverse ages under similar tectonic settings. Kieselguhr sediments in the Laiwu Basin are younger than those in the Shanwang Basin.

关 键 词：化学地层 微量元素 锆石 U—Pb定年 山旺组 莱芜盆地 山东 

分 类 号：P534.62[天文地球—古生物学与地层学]