Global Climatic Consequence of CO2 Released During Eocene Regional Metamorphism

[304939] Kerrick碰撞造山作用可能提供了一个气候上重要的CO2来源，因此需要重新研究造山和造山变质作用在长期全球变化中的作用。始新世古大气CO2水平的升高可能是始新世区域变质作用释放的CO2影响了特提斯和环太平洋造山带的广泛部分。根据地质记录，仅特提斯喜马拉雅造山带的区域变质作用就可能提供了足够的二氧化碳，产生重大的始新世气候影响。在递进的区域变质作用期间，碳酸盐和碳质岩性（如硅质白云岩、泥灰岩、黑色页岩）中脱碳反应释放到大气中的二氧化碳的数量和通量是一个被忽视的问题。根据喜马拉雅造山带受始新世变质作用影响的规模、参与变质作用的偏碳酸盐和石墨岩的比例以及对进变质作用持续时间的地质年代学分析，始新世大气可能接收了大量变质CO2 （1019 mol /Ma）。地质年代学分析显示，特提斯造山带和环太平洋造山带内的许多地区在变质高峰时代（即40-50 Ma）上具有显著的相似性，从而支持始新世主要区域变质作用的概念。我们提出的跨学科研究主要有两个重点：(1)分析地质记录以量化始新世变质二氧化碳的产量和速率；(2)模拟变质二氧化碳通量对始新世大气的影响。＊＊＊

9304939 Kerrick Collisional orogenesis may provide a climatically important source of CO2, thus requiring a re-examination of the role of mountain building and orogenic metamorphism in long-term global change. The elevated paleoatmospheric CO2 levels proposed for the Eocene may have resulted from CO2 released during Eocene regional metamorphism that affected extensive segments of the Tethys and Circum-Pacific orogenic belts. Based on the geologic record, the regional metamorphism in the Tethyan Himalayan orogen alone may have provided enough CO2 to produce a significant Eocene climatic impact. The quantities and fluxes of CO2 released to the atmosphere by decarbonation reactions in carbonate and carbonaceous lithologies (e.g., siliceous dolomites, marls, black shales) during prograde regional metamorphism represents a much neglected problem. From estimates of the size of the Himalayan orogen affected by Eocene metamorphism, the proportion of metacarbonate and graphitic rocks involved in this metamorphism, and geochronologic analysis of the duration of prograde metamorphism, and Eocene atmosphere could have received a large flux of metamorphic CO2 ( 1019 moles/Ma). Geochronologic analyses reveal a remarkable similarity in peak metamorphic ages (i.e., 40-50 Ma) for many areas within the Tethys and Circum-Pacific orogens, thus supporting the concept of a major, world-wide Eocene regional metamorphism. There are two primary thrusts of our proposed interdisciplinary research: (1) analysis of the geologic record to quantify the amount and rate of metamorphic CO2 production during the Eocene, and (2) modeling the impact of metamorphic CO2 fluxes on the Eocene atmosphere. ***