The Fate of Subducted Carbon Dioxide During Metamorphism, Syros and Tinos Islands, Greece

地球的俯冲带以深海海沟为标志，在那里一个构造板块下沉（俯冲）到另一个板块之下，进入地幔，通常以每年几英寸的速度下沉。俯冲带具有重要的社会意义，因为它们是世界上最大的地震（包括产生致命海啸的地震）和最具破坏性的火山的所在地。此外，俯冲是地质碳循环的驱动因素，而地质碳循环是地球温带气候和生命的先决条件。全球每年大约有一亿吨储存在岩石中的碳被俯冲。然而，主要的分歧在于，这些碳（主要以二氧化碳的形式）究竟有多少从俯冲带释放出来，并回到地表。这些二氧化碳是大部分被带到地幔深处，还是大部分上升并最终与大气和水圈相互作用？提议的工作将通过确定希腊Syros和Tinos岛引人注目的化石俯冲复合体所记录的碳运输的性质、过程和数量来阐明这些问题。这是量化自然和人为（人类）对气候和气候变化长期演变的贡献的必要步骤。提出的工作是一项基于野外的变质脱碳过程的岩石学研究，涉及蛇纹岩-绿泥石（Syros, Tinos）和变质沉积（Tinos）与变质火山岩、变质碎屑岩和变质碳酸盐岩穿插或构造并置。含碳酸盐岩性的封闭和开放系统行为将被量化，以确定外部流体的渗透程度，并绘制流体组成和时间积分的脱挥发通量图。这是以前在俯冲复合体的区域尺度上没有做过的。该提议的目标将通过基于测量岩石和矿物成分的流体化学热力学建模来实现；流体包裹体的拉曼光谱，以识别简单的（例如水-二氧化碳）或更复杂的含有溶解溶质的流体；氧和碳稳定同位素工作评估流体来源和流动途径；矿物和大块岩石的化学分析，以确定交代反应。二氧化碳运输的定量估计将为地质碳循环模型提供重要的新输入。这项工作将支持一名来自一个代表性不足的科学群体的博士生和几名本科生，并为耶鲁皮博迪自然历史博物馆和希腊克里特岛自然历史博物馆制作有关碳循环的教育模块。

Earth's subduction zones are marked by the deep ocean trenches where one tectonic plate sinks (subducts) beneath another into Earth's mantle, commonly at speeds of inches per year. Subduction zones are of critical societal importance because they host the world's largest earthquakes - including those that produce deadly tsunamis - and the most destructive volcanoes. Moreover, subduction is a driver of the geological carbon cycle, a prerequisite for Earth's temperate climate and life. Roughly a hundred million tons of carbon stored in rocks are subducted each year across the globe. Yet major disagreements surround how much of this carbon, mostly in the form of carbon dioxide, is actually released from subduction zones to make the journey back to the surface. Is this carbon dioxide largely taken deep into Earth's mantle, or does the bulk of it ascend to ultimately interact with the atmosphere and hydrosphere? The proposed work will shed light on these questions by determining the nature, processes, and amounts of carbon transport recorded by the spectacularly-exposed fossil subduction complexes of Syros and Tinos islands, Greece. This is a necessary step for quantifying natural and anthropogenic (human) contributions to the long-term evolution of climate and climate change. The proposed work is a field-based petrological study of metamorphic decarbonation processes involving serpentinite-chlorite mélange (Syros, Tinos) and metasedimentary mélange (Tinos) intercalated or tectonically juxtaposed with metavolcanic, metaclastic, and metacarbonate rocks. The closed- and open-system behavior of carbonate-bearing lithologies will be quantified to determine the degree of external fluid infiltration and make maps of fluid composition and time-integrated devolatilization fluxes. This has not been done before at a regional scale in subduction complexes. The proposal goals will be achieved via thermodynamic modeling of fluid chemistry based on measured rock and mineral compositions; Raman spectroscopy of fluid inclusions to identify simple (e.g. water-carbon dioxide) or more complex fluids containing dissolved solutes; oxygen and carbon stable isotope work to assess fluid sources and flow pathways; and mineral and bulk-rock chemical analyses to determine metasomatic reactions. Quantitative estimates of carbon dioxide transport will provide important new inputs to models of the geologic carbon cycle. The work will support a Ph.D. student from an under-represented group in science as well as several undergraduates, and produce educational modules about the carbon cycle for both the Yale Peabody Museum of Natural History and the Natural History Museum of Crete, Greece.