Long-term storage of subduction-related volatiles in Northern Victoria Land lithospheric mantle: Insight from olivine-hosted melt inclusions from McMurdo basic lavas (Antarctica)
Long-term storage of subduction-related volatiles in Northern Victoria Land lithospheric mantle: Insight from olivine-hosted melt inclusions from McMurdo basic lavas (Antarctica)
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维多利亚州北部岩石圈地幔中与俯冲相关的挥发物的长期储存：来自麦克默多基性熔岩（南极洲）的橄榄石熔体包裹体的见解
DOI：
10.1016/j.lithos.2020.105826
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发表时间：
2020
期刊：
影响因子：
3.5
通讯作者：
Coltorti, M.
中科院分区：
文献类型：
--
作者：
Giacomoni, P.P.;Bonadiman, C.;Casetta, F.;Faccini, B.;Ferlito, C.;Ottolini, L.;Zanetti, A.;Coltorti, M.
采用二次离子质谱法（西姆斯）测定了北方维多利亚地新生代碱性火山岩中橄榄石熔融包裹体（MI）中H2O、CO2、F、Cl和S的含量。最不脱气的H2O和CO2值变化从1.14至2.64重量% H2O和2320至3900 ppm CO2最少分化碱性玄武岩和玄武岩，分别。同一种MI的F和Cl含量分别为471 ~ 888和474 ~ 1135，而有些MI的F含量可达1377，Cl含量可达1336。A H2O/（H2O + CO2）的摩尔比从0.88到0.92进行了测定，并考虑到MI与最高的水含量，在熔体中的CO2含量高达4400和8800 ppm的玄武岩和玄武质组合物进行推断。假设这些岩浆是由约3%至7%的部分熔融产生的，地幔源中的挥发分含量进行了估算，并与大量夹带在麦克默多基性熔岩中的含角闪石地幔捕虏体的估算值进行了比较。这两种方法在获得以下值时趋于一致：H2O = 1160 ± 436 ppm; CO2= 304 ± 64 ppm。由于角闪石中F和Cl含量及其模式含量的不确定性，F和Cl的计算值与DMM的计算值有较大差异，CO2/Nb和CO2/Ba比值低于DMM的计算值，H2O/Ce比值高于DMM的计算值。表明NVL新生代碱性岩浆活动可能起源于一个由60 - 70%的富集地幔（EM）和40 - 30%的富集地幔组成的富集地幔源区。通过对Li、K、Cl、Ba、Nb、Dy和Yb等与流体有关的高不相容和不动/低不相容元素的全球对比，提出在新生代大陆裂谷作用开始之前，罗斯俯冲事件（~500 ~ 100 Ma）对岩石圈地幔的挥发分收支起了重要作用。
H2O, CO2, F, Cl and S concentrations in olivine-hosted melt inclusions (MI) from Cenozoic alkaline volcanics of Northern Victoria Land (NVL, Antarctica) were determined by Secondary Ion Mass Spectrometry (SIMS). The most undegassed H2O and CO2values varies from 1.14 to 2.64 wt% H2O and from 2320 to 3900 ppm CO2for the least differentiated alkaline basalts and basanites, respectively. The same MI have F and Cl contents varying from 471 to 888 and from 474 to 1135 respectively, although some other MI can get up to 1377 of F and 1336 of Cl. A H2O/(H2O + CO2) molar ratios from 0.88 to 0.92 were determined, and taking into account the MI with the highest water content, a CO2content in the melts up to 4400 and 8800 ppm for basaltic and basanitic compositions were inferred. Assuming that these magmas were produced by about 3 to 7% of partial melting, the volatile content in the mantle sources were estimated and compared with the estimates obtained from amphibole-bearing mantle xenoliths abundantly entrained in the McMurdo basic lavas. The two approaches converge in obtaining the following values: H2O = 1160 ± 436 ppm; CO2= 304 ± 64 ppm. Some discrepancies are observed for F and Cl, mainly due to the uncertainties in the F and Cl contents of amphibole and its modal content, both parameters spanning a rather large range.The resulting CO2/Nb and CO2/Ba ratios are lower and H2O/Ce higher than those estimated for Depleted MORB Mantle (DMM), suggesting that the NVL Cenozoic alkaline magmatism could be originated by an enriched mantle source composed by 60 to 70% Enriched Mantle (EM) and from 40 to 30% DMM.A global comparison of fluid-related, highly incompatible and immobile/low incompatible elements such as Li, K, Cl, Ba, Nb, Dy and Yb allow to put forward that the prolonged (~500 to 100 Ma) Ross subduction event played a fundamental role in providing the volatile budget to the lithospheric mantle before the onset of the Cenozoic continental rifting.
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发表时间：
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期刊：
影响因子：
--
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通讯作者：
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影响因子：
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作者：
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