摘要
大石桥组是辽河群中一个重要的含矿层位,其岩性主要由白云石大理岩、方解石大理岩、云母片岩组成.在本次研究中,在辽阳南部八会镇辽河群大石桥组地层大理岩中首次发现有一层酸性火山岩夹层,岩性为流纹质角砾凝灰岩.根据野外产状判断,酸性火山岩与大理岩为同时沉积.清晰的振荡环带及比较高的Th/U比值,显示流纹质角砾凝灰岩的锆石为岩浆锆石,对其进行LA-ICP-MS U-Pb测年,结果显示其成岩年龄为2171±11 Ma,首次精确地厘定了大石桥组的形成时代.此年龄也进限定了置于大石桥组之下的浪子山组、里尔峪组、高家峪组等3个地层的沉积时限为2171 Ma之前.
Dashiqiao Formation, the important ore-bearing horizon in Liaohe Group, is lithologically composed of dolomite marble, calcite marble and mica schist. In this study, a layer of acidic volcanic interbed, rhyolitic breccia tuff, is founded in the marble of Dashiqiao Formation for the first time in Bahui Town, southern Liaoyang City. Based on the field occurrence, the acidic volcanic rock and the marble were deposited simultaneously. The clear oscillatory zoning and high Th/U ratio show that the zircons from the rhyolitic breccia tuff are magmatic origin. The LA-ICP-MS zircon U-Pb dating yields the age of 2171±11 Ma, which is the first accurate age for the Dashiqiao Formation. This age also constrains the sedimentary time of Langzishan Formation, Lieryu Formation and Gaojiayu Formation, which underlie the Dashiqiao Formation, to before 2171 Ma.
出处
《地质与资源》
CAS
2017年第2期105-110,共6页
Geology and Resources
基金
中国地质调查局地质大调查项目(12120113053400、121201007000150008-05、12120114055501)
中国地质调查局综合研究项目(12120113058400)
关键词
酸性火山岩
锆石U-PB
大石桥组
辽河群
辽阳地区
acidic volcanic rock
zircon U-Pb
Dashiqiao Formation
Liaohe Group
Liaoyang area
