鄂北大洪山地区～817Ma洋岛玄武岩的发现及意义
发布时间：2019-01-08 13:47
【摘要】：最新地质调查发现鄂北大洪山地区存在晋宁期的俯冲增生杂岩,其主体以一套弧前碎屑岩(复理石)为基质,夹大量白云岩、砾岩、硅泥质岩、辉长岩、辉绿岩、玄武岩等岩块,岩块与基质、岩块与岩块之间以断层接触。杂岩中大量的镁铁质岩岩块可能形成于洋中脊、洋内弧、洋岛等不同类型与洋盆演化相关的构造环境,首次报道绿林地区杂岩中一套呈岩块产出的洋岛碱性玄武岩。地球化学方面,绿林地区玄武岩具低K_2O、高TiO_2、Nb/Y=0.88~1.06、轻稀土元素强烈富集、重稀土元素明显亏损等特点,整体与夏威夷洋岛碱性玄武岩的地球化学特征基本一致。绿林玄武岩LA-ICP-MS锆石U-Pb测年结果显示,17个测点加权平均年龄为(817.1±7.2)Ma(MSWD=3.3),代表绿林玄武岩的形成年龄。因此绿林玄武岩可能代表晋宁期的洋岛碱性玄武岩残块,成岩岩浆来源于富集地幔。绿林洋岛碱性玄武岩与大洪山地区其他洋岛玄武岩类岩石组合可能同是洋盆消减过程中的洋壳物质残余,不同类型洋岛玄武岩的出现是洋盆演化阶段性、复杂性的体现,这些岩石建造的厘定为大洪山存在晋宁期缝合带的观点提供了强有力的证据。
[Abstract]:The latest geological investigation found that there were subducted accretive complex rocks of Jinning period in the Dahongshan area of northern Hubei Province, the main body of which was a set of pre-arc clastic rocks (clastic rocks), with a large amount of dolomite, conglomerate, sillimanite, gabbro, diabase, etc. Basalt and other rock blocks, rock and matrix, rock block to rock block contact with fault. A large number of mafic rock blocks in the complex may form different types of tectonic environments related to the evolution of oceanic basins, such as Yu Yang middle ridge, intraoceanic arc and oceanic island. It is the first time to report a set of oceanic island alkaline basalts in the complex rocks in the greenlin area. Geochemically, basalts in the Greenlin area are characterized by low K _ 2O, strong enrichment of high TiO_2,Nb/Y=0.88~1.06, light rare earth elements, and obvious depletion of heavy rare earth elements. The geochemical characteristics of alkaline basalts in the whole ocean island of Hawaii are basically consistent. The LA-ICP-MS zircon U-Pb dating results of the greenlin basalt show that the weighted mean age of 17 sites is (817.1 卤7.2) Ma (MSWD=3.3), which represents the age of formation of the greenlin basalt. Therefore the greenlin basalt may represent the oceanic island alkaline basalt remnant in Jinning period and the diagenetic magma originated from the enriched mantle. The basalt assemblages of Lulingyang Island and other oceanic island basalts in Dahongshan area may be the remnants of oceanic crust material in the process of oceanic basin subduction, and the appearance of different types of oceanic island basalts is the embodiment of stage and complexity of oceanic basin evolution. The determination of these rock formations provides strong evidence for the existence of the Jinning suture zone in Dahongshan.
【作者单位】： 湖北省地质调查院;
【基金】：湖北省地质局科技项目(KJ2015-1) 中国地质调查局项目(12120113012800;DD20160030-06)
【分类号】：P588.145
本文编号：2404683
[Abstract]:The latest geological investigation found that there were subducted accretive complex rocks of Jinning period in the Dahongshan area of northern Hubei Province, the main body of which was a set of pre-arc clastic rocks (clastic rocks), with a large amount of dolomite, conglomerate, sillimanite, gabbro, diabase, etc. Basalt and other rock blocks, rock and matrix, rock block to rock block contact with fault. A large number of mafic rock blocks in the complex may form different types of tectonic environments related to the evolution of oceanic basins, such as Yu Yang middle ridge, intraoceanic arc and oceanic island. It is the first time to report a set of oceanic island alkaline basalts in the complex rocks in the greenlin area. Geochemically, basalts in the Greenlin area are characterized by low K _ 2O, strong enrichment of high TiO_2,Nb/Y=0.88~1.06, light rare earth elements, and obvious depletion of heavy rare earth elements. The geochemical characteristics of alkaline basalts in the whole ocean island of Hawaii are basically consistent. The LA-ICP-MS zircon U-Pb dating results of the greenlin basalt show that the weighted mean age of 17 sites is (817.1 卤7.2) Ma (MSWD=3.3), which represents the age of formation of the greenlin basalt. Therefore the greenlin basalt may represent the oceanic island alkaline basalt remnant in Jinning period and the diagenetic magma originated from the enriched mantle. The basalt assemblages of Lulingyang Island and other oceanic island basalts in Dahongshan area may be the remnants of oceanic crust material in the process of oceanic basin subduction, and the appearance of different types of oceanic island basalts is the embodiment of stage and complexity of oceanic basin evolution. The determination of these rock formations provides strong evidence for the existence of the Jinning suture zone in Dahongshan.
【作者单位】： 湖北省地质调查院;
【基金】：湖北省地质局科技项目(KJ2015-1) 中国地质调查局项目(12120113012800;DD20160030-06)
【分类号】：P588.145
【相似文献】
相关期刊论文 前2条
1 杨鸿达;湖北大洪山区域地质问题[J];南京大学学报(自然科学版);1956年05期
2 董云鹏,张国伟,柳小明,赖绍聪;鄂北大洪山地区“花山群”的解体[J];中国区域地质;1998年04期
，本文编号：2404683
本文链接：https://www.wllwen.com/kejilunwen/diqiudizhi/2404683.html
