摘要
在前人研究的基础上,对本巴图组的野外地质特征、岩石类型、岩石组合、锆石年代学等进行了研究。镜下特征显示本巴图组砂岩主体为岩屑晶屑含砾砂岩;碎屑锆石阴极发光图像显示,它们多具有震荡生长环带或条痕状吸收.Th/U比值为0.06~1.03(平均0.55),具有岩浆锆石的典型特点。应用LA—ICP—MS测年技术对本巴图组进行了碎屑锆石分析.其^206Pb/^238U年龄可以分为5组:①319~451Ma,峰期年龄为363Ma;②457~543Ma,峰期年龄为513Ma;③724-996Ma,峰期年龄为945Ma:④1031~1836Ma,峰期年龄为1572Ma;⑤2469-2505Ma,峰期年龄为2487Ma。年龄分布的意义:研究区本巴图组沉积的时间下限应为319Ma之后;457-543Ma发生泛非期构造热事件,沉积物源主要来源于佳~蒙地块;另外几组峰值年龄945Ma、1572Ma和2487Ma主要反映了佳-蒙地块基底的年龄信息。
Based on the previous research, the authors investigated the field geological characteristics, lithologies, rock assemblages and zircon LA-LCP-MS U-Pb data from the Benbatu Formation. The sandstone in this formation are chiefly of lithic-crystal pebbled sandstone. The zircons fi:om sandstone show oscillatory growth zoning or striped absorption in cathodoluminescence images, together with their high Th/U ratios (0.06-1.03). These features indicated a magmatic origin. The zircon U-Pb dating results show that 39 analyzed spots can be divided into five groups, i.e., 319-451 Ma (peak at 363 Ma), 457-543 Ma (peak at 513 Ma), 724-996 Ma (peak at 945 Ma), 1031-1836Ma (peak at 1572 Ma) and 2469-2505Ma (peak at 2487 Ma). These ages indicate that: (1) Benbatu Formation was deposited after 319 Ma; (2) the presence of the detrital zircons with the ages of 457-543 Ma, indicating the Pan-African tectonic events, suggested that these rocks were sourced from the Jiamusi-Mongolia massif; (3) the others age population, such as 945 Ma, 1572 Ma and 2487 Ma, should display the age information of the basement of the Jiamusi-Mongolia massif.
出处
《地质通报》
CAS
CSCD
北大核心
2011年第2期278-290,共13页
Geological Bulletin of China
基金
国土资源部油气专项(编号:2009GYXQ12-01)
国家自然科学基金项目<"兴蒙海槽"晚古生代构造演化>(批准号:40739905)
<苏鲁地区新元古界的碎屑锆石年代学研究及其大地构造意义>(批准号:40872121)
关键词
本巴图组
碎屑锆石
年代学
构造背景
松辽盆地西部
Benbatu Formation
detrital zircon
chronology
tectonic setting
western Songliao Basin, NE China