辽东宽甸地区硼酸盐矿床成矿时代的限定：来自SHRIMP锆石U-Pb年代学和硼同位素地球化学的制约  

The Forming Age of the Borate Deposits in Kuandian Area,Eastern Liaoning Province:Constrains from the SHRIMP U-Pb Data and Boron Isotopic Composition

作　　者：胡古月[1] 李延河[1] 范润龙 王天慧[3] 范昌福[1] 王彦斌[2] 

机构地区：[1]中国地质科学院矿产资源研究所、国土资源部成矿作用与资源评价重点实验室,北京100037 [2]中国地质科学院地质研究所、北京离子探针中心,北京102206 [3]北京科技大学、土木与环境工程学院,北京100083

出　　处：《地质学报》2014年第10期1932-1943,共12页Acta Geologica Sinica

基　　金：国土资源部公益性行业科研专项经费项目(项目号:201211074-2)资助

摘　　要：辽宁宽甸地区砖庙硼矿区的硼矿体呈层状或透镜状赋存于古元古代辽河群里尔峪组火山—沉积建造下部的蛇纹石化大理岩之中。本研究对矿区内外的伟晶岩和变粒岩中的电气石进行了LA-MC-ICP-MS硼同位素微区原位测试,分析了矿床成因;同时对栾家沟矿段矿体上盘含电气石变粒岩和斜长角闪岩进行了SHRIMP锆石U-Pb定年,探讨了成矿时代。得到以下数据和认识:1矿区伟晶岩中电气石的δ11 B为10.9‰~12.7‰,变粒岩中电气石的δ11B为5.7‰~7.6‰,矿区外伟晶岩中电气石的δ11B为-9.9‰^-9.2‰,变粒岩中电气石的δ11 B为-8.3‰^-5.9‰。硼同位素组成往外降低的现象说明,围岩及侵位其中的伟晶岩的B同位素组成均受硼矿床影响,硼矿可能是海相蒸发沉积成因;2含电气石变粒岩核部岩浆锆石的207 Pb/206 Pb加权平均年龄为2174±10Ma,代表了辽吉裂谷早期的火山喷发时代,亦大致代表了初始的含硼蒸发岩的沉积时代上限,根据硼同位素研究结果,可将宽甸地区硼矿的初始沉积成矿时代限定在2.17Ga;3斜长角闪岩重结晶锆石207 Pb/206 Pb加权平均年龄为1869±28Ma,代表了吕梁运动所引起的区域构造热事件和混合岩化作用的时间。The borate ore bodies in Zhuanmiao boron district are locate at the lower stratums of volcanicsedimentary Lieryu Formation of Kuandian country of eastern Liaoning Province,and exhibit layered or lentoid structures in the wall rocks of serpentinized marbles.In order to get the original ore-forming environment,applied LA-MC-ICP-MS in-situ technology to analyze the boron isotopic composition of tourmalines that locate inside or outside the Zhuanmiao boron district,while in order to get the original ore-forming time,applied SHRIMP zircon U-Pb dating technology to analyze the leptynite（13LJG-1）and amphibolite（13LJG-13）that located at the hanging wall of the borate ore bodies.we get the following data and understanding：①theδ11B values of tourmalines which inside the borate ores are range from 10.9to 12.7‰,inside the wall rocks are range from 5.7‰ to 7.6‰,while outside the boron district,the tourmalines in pegmatites are range from-9.9‰to-9.2‰ and in leptynites are range from-8.3‰to-5.9‰.The declining trend of boron isotopic compositions for tourmalines in Zhuanmiao boron district indicates that the boron isotopic composition of wall rocks and the pegmatites therein are affected by the ore bodies and the borate deposit may original come from marine evaporites.② eight analysis on cores of oscillatory zoned zircon grains of leptynite（13LJG-1）yielded a weighted 207Pb/206 Pb mean age of 2174±10Ma,represents the early volcanic epoch of Liaoji rift and the upper limit of the ore forming age of the evaporative borate deposits;③ eleven analysis on recrystallized zircon grains of amphibolite（13LJG-19）yielded a weighted 207Pb/206 Pb mean age of 1869±28Ma,represents a major late paleoproterozoic migmatization of Lvliang movement in Kuandian area.

关 键 词：辽吉裂谷 辽河群 硼酸盐矿床 SHRIMP锆石U-PB定年 硼同位素 

分 类 号：P619.21[天文地球—矿床学] P597[天文地球—地质学]