Iranian Neo-Tethyan magmas as a significant CO2 source during the Middle Eocene Climatic Optimum

IF 2.5 2区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS
Lea Ostorero , Rosario Esposito , Pierre Bouilhol , Paolo Ballato , Veleda Astarte Müller , Maria Luce Frezzotti , Pietro Sternai
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Abstract

CO2 emissions from magmatic arcs can affect the atmosphere composition, thereby driving long-term global climate changes. Early Cenozoic climate trends are generally associated with changes in global silicate weathering related to Neo-Tethyan geodynamics, but the likely climatic effects of changes in degassing from Neo-Tethyan magmatic arcs have been poorly quantified. Here, we characterize the petrography and provide the first measures of the volatile content (CO2, H2O, F, Cl, and S) of pre-eruptive melts based on glassy, bubble-bearing and reheated melt inclusions within plagioclase and clinopyroxene crystals in Early Cenozoic trachyandesites from the Alborz and Tabriz regions (Iran). CO2 concentrations in these melt inclusions reach up to 6733 ppm, thus providing a minimum estimate of the total amount of CO2 degassed from Iranian magmas during the middle-late Eocene of 1.01 × 1019 (± 4.04 × 1017) g CO2, with a total C flux released of 0.306 (± 0.012) Mt. C/yr, which is within the carbon imbalance predictions estimated based on other proxies. Our measures validate earlier hypotheses that magmatic CO2 degassing from the targeted igneous provinces contributed to the Middle Eocene Climatic Optimum. Further measurements of the volatiles content of Neo-Tethyan magmas are thus critical to assess the drivers of Early Cenozoic climate trends and understand the global volatile cycling over geological timescales.
伊朗新特提斯岩浆在中始新世气候最适期是一个重要的CO2源
岩浆弧排放的二氧化碳会影响大气成分,从而推动长期的全球气候变化。早新生代气候趋势通常与新特提斯地球动力学相关的全球硅酸盐风化变化有关,但新特提斯岩浆弧脱气变化可能对气候的影响却很少量化。在这里,我们描述了岩石学特征,并提供了喷发前熔体挥发性含量(CO2, H2O, F, Cl和S)的第一个测量方法,这些挥发性含量是基于来自伊朗Alborz和Tabriz地区早新生代粗质山岩中斜长石和斜辉石晶体中的玻璃状,含气泡和再加热的熔体包裹体。这些熔体包裹体中的CO2浓度高达6733 ppm,从而提供了始新世中晚期伊朗岩浆脱气总量1.01 × 1019(±4.04 × 1017) g CO2的最小估计,总碳通量为0.306(±0.012)Mt. C/yr,这在基于其他代用物估计的碳不平衡预测范围内。我们的研究结果验证了先前的假设,即来自目标火成岩省的岩浆CO2脱气有助于中始新世气候最佳。因此,对新特提斯岩浆挥发物含量的进一步测量对于评估早期新生代气候趋势的驱动因素和了解地质时间尺度上的全球挥发物循环至关重要。
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来源期刊
Lithos
Lithos 地学-地球化学与地球物理
CiteScore
6.80
自引率
11.40%
发文量
286
审稿时长
3.5 months
期刊介绍: Lithos publishes original research papers on the petrology, geochemistry and petrogenesis of igneous and metamorphic rocks. Papers on mineralogy/mineral physics related to petrology and petrogenetic problems are also welcomed.
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