Determination of high resolution thermal and tectonic history of Archean terranes: Development of a tool through a case study from the Western Dharwar Craton and the Coorg block in S. India

确定太古代地体的高分辨率热和构造历史：通过西达瓦尔克拉通和印度南部库格地块的案例研究开发工具

• 批准号: 276958716
• 负责人: Professor Dr. Sumit Chakraborty, Ph.D.
• 金额: --
• 依托单位: Institut für Geologie, Mineralogie und Geophysik
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/276958716?language=en
• 关键词: Determination; resolution; thermal; tectonic; history

The time period around 3.0 Ga is a critical period in the history of the Earth because in many models it is thought to be the period when a transition occurred to present day plate tectonic styles. This is considered to be the result of a shift in the balance between heat generation and heat loss; heat generation was thought to have dominated over heat loss before 3.0 Ga. However, the transition itself is thought to have been rapid (within < 0.5 Ga), and it is not clear if it was global and synchronous. The resolution of isotopic clocks do not always suffice to resolve the various closely spaced (in time) events in these ancient rocks. Therefore, it is necessary to develop new tools to quantify and understand such thermal processes better. We have developed the approach of sequential kinetic modelling (modelling the diffusive modification of compositional zoning in minerals in stages) and applied it successfully to present day volcanic systems as well as in ultrahigh temperature metamorphic systems. In this project we wish to use this tool to study the thermal evolution (heating/cooling and burial/exhumation histories) of a set of rocks from the Western Dharwar Craton and the Coorg Block in South India to characterize their tectonic style. These rocks experienced several episodes of thermal metamorphism in the critical period between 3.3. and 2.5 Ga, and contain mineral assemblages in which sequential kinetic modelling can be applied. Our objective in this project is to (a) obtain high resolution thermal histories of two adjacent blocks with contrasting signatures from the same time period, and (b) use these examples to develop the tool for general use in Archean rocks, so that it may be used in other Archean terranes as well in later projects to quantify the global thermal evolution during this critical period of the history of the Earth.

3.0 GA左右的时间段是地球历史上的关键时期，因为在许多模型中，人们认为这是当前日板构造样式的过渡时期。这被认为是热量产生和热量损失之间平衡的结果。人们认为热产生在3.0 ga之前占主导地位。但是，过渡本身被认为是迅速的（<0.5 ga之内），尚不清楚它是否是全球性和同步性的。同位素钟的分辨率并不总是足以解决这些古老岩石中的各种紧密间隔（随时间）。因此，有必要开发新工具来更好地量化和理解此类热过程。我们已经开发了顺序动力学建模的方法（在阶段对矿物质中的组成分区进行扩散修饰），并成功地应用于当今的火山系统以及超高温度变态系统。在这个项目中，我们希望使用此工具来研究来自西部Dharwar Craton和印度南部的Coorg Block的一组岩石的热演化（加热/冷却和埋葬/挖掘历史），以表征其构造风格。这些岩石在3.3之间的关键时期经历了几种热变质事件。和2.5 ga，并包含矿物组合，可以在其中应用顺序的动力学建模。我们在该项目中的目标是（a）获得两个相邻块的高分辨率热历史，并从同一时期进行对比签名，并且（b）使用这些示例来开发该工具，以便在Archean Rocks中进行一般用途，以便它可以在以后的项目中，也可以在其他大帝地层中使用，以量化地球历史的这个关键时期。