Tectonic origin of supra-subduction zone ophiolites from the three-dimensional geochemical structure of the lava pile

从熔岩堆三维地球化学结构看超俯冲带蛇绿岩的构造成因

基本信息

批准号：
290488493
负责人：
Privatdozent Dr. Marcel Regelous
金额：
--
依托单位：
Geotieteiden ja maantieteen osasto
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2015
资助国家：
德国
起止时间：
2014-12-31 至 2019-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/290488493?language=en
关键词：
Tectonic origin supra subduction zone

项目摘要

Ophiolites are fragments of oceanic crust preserved on land, and are often used to infer the internal structure of the oceanic crust and the processes by which it is formed. However, most ophiolites were not formed in typical mid-ocean ridge settings, and instead appear to have formed close to former subduction zones. The exact tectonic setting in which they were formed has been debated for over 40 years. If ophiolites represent fore-arc crust formed during subduction initiation events, then they provide insights into the initiation of subduction zones, an outstanding unresolved question in plate tectonics. If ophiolites were formed in back-arc or plate edge settings they may represent useful analogues for the internal structure of oceanic crust. If they were formed at a ridge-trench-trench or ridge-trench-transform triple junction then they could be used to investigate mantle wedge structure and processes. Different tectonic models predict different geochemical variations in ophiolite lavas with space and time. We will map out the 3D gechemical structure of the Troodos Ophiolite of Cyprus, one of the best preserved and exposed ophiolites. We will use major and trace element microanaysis of fresh volcanic glass in order to avoid the effects of alteration. Detailed high resolution sampling of sections through the Troodos volcanic section on both the northern and southern margins of the ophiolite will be used to determine the chemical evolution of magmatism. New 39Ar-40Ar ages for lavas from different stratigraphic levels in the Troodos lava sequence will be used to determine the age and duration of the volcanism, and rates of chemical evolution of magmatism with time. Our new geochemical and geochronological data will be used to test hypotheses for the tectonic origin of the Troodos ophiolite.

蛇晶是保存在陆地上的海洋壳的碎片，通常用于推断海洋壳的内部结构及其形成的过程。但是，大多数蛇绿岩不是在典型的中山脊环境中形成的，而是似乎已经形成了以前的俯冲带。他们成立的确切构造环境已有40多年的辩论。如果蛇晶代表在俯冲起始事件中形成的前弧形外壳，则它们为俯冲带的启动提供了见解，这是板块构造中的一个未解决的未解决的问题。如果在后弧或板边缘设置中形成蛇纤维，则可能代表海洋外壳内部结构的有用类似物。如果它们是在山脊 - 沟槽或脊 - 沟通式转移三连接处形成的，则可以用于研究地幔楔形结构和过程。不同的构造模型可以预测具有空间和时间的蛇绿岩熔岩中不同的地球化学变化。我们将绘制塞浦路斯的Troodos Ophiolite的3D Gechemical结构，这是保存最佳和暴露的蛇绿岩之一。我们将使用新鲜火山玻璃的主要和痕量元素微动物，以避免改变的影响。详细的高分辨率采样通过troodos火山截面上的山葡萄晶和南部边缘的troodos火山截面将用于确定岩浆的化学演化。新的39AR-40AR年龄用于troodos熔岩序列中不同地层水平的熔岩年龄，以确定火山症的年龄和持续时间，以及随着时间的推移的岩浆化学演化速度。我们的新的地球化学和地质学数据将用于检验troodos ophiolite的构造起源的假设。