气候变化领域集成服务门户(CCPortal): Melt addition to mid-ocean ridge peridotites increases spinel Cr# with no significant effect on recorded oxygen fugacity

CCPortal

DOI	10.1016/j.epsl.2021.116951
	Melt addition to mid-ocean ridge peridotites increases spinel Cr# with no significant effect on recorded oxygen fugacity
	Birner S.K.; Cottrell E.; Warren J.M.; Kelley K.A.; Davis F.A.
发表日期	2021
ISSN	0012821X
卷号	566
英文摘要	Mid-ocean ridge peridotites record significantly greater variability in major and trace elements, isotopic compositions, and thermodynamic properties such as oxygen fugacity (fO2) than do their basaltic counterparts. This variability may derive from modern ridge processes related to melting and melt-rock interaction or from long-lived source heterogeneity related to recycled material or ancient melting events. In this study, we investigate variations in spinel geochemistry as well as silicate major and trace element chemistry and oxygen fugacity of a suite of peridotites from a single segment of the Southwest Indian Ridge (SWIR). We present new petrographic analysis and trace element data for samples with previously-published fO2 results and combine this with new data for a suite of SWIR gabbro-veined peridotites. We find that SWIR residual lherzolites record low spinel Cr# (Cr# = 100*Cr/(Cr+Al) < 30) and represent low to moderate degrees of melting (∼5-8%) beneath the ridge axis, with no change in oxygen fugacity during melting. In contrast, a subset of SWIR peridotites with high spinel Cr# (Cr#>30) record both melt extraction as well as melt-rock interaction. In these samples, spinel Cr# has been substantially elevated by reaction of spinel to form plagioclase during melt addition, complicating the use of spinel Cr# in mid-ocean ridge peridotites as a proxy for degree of melt extraction alone. While spinel Cr# remains a robust proxy for melt extraction within residual, non-melt-influenced samples, mid-ocean ridge peridotites must first be evaluated to ensure that modification by melt-rock reaction has not occurred. Although addition of MORB melt to a peridotite residue modifies spinel Cr#, this melt addition does not result in significant changes to the fO2 recorded by the peridotite. Residual SWIR lherzolites record fO2 of 0.66±0.39 relative to the quartz-fayalite-magnetite buffer (QFM), statistically indistinguishable from melt-influenced and veined SWIR samples (QFM+1.13±0.61). In contrast to other tectonic settings, such as subduction zones, ocean islands, and continental cratons—locations where peridotite is oxidized by petrogenetically unrelated, presumably high-fO2 melts/fluids—ridge peridotites interact with MORB, which has little to no oxidizing power over its own mantle residues. Thus, modern processes beneath the ridge modify peridotite major and trace elements, but do not generate variability in oxygen fugacity. © 2021 The Authors
关键词	mantle mid-ocean ridges MORB oxygen fugacity peridotite spinel
英文关键词	Extraction; Feldspar; Magnetite; Melting; Oceanography; Structural geology; Submarine geology; Trace elements; Major and trace elements; Mantle; Melt extraction; Melt/rock interaction; Mid-ocean-ridge; MORB; Oxygen fugacity; Peridotite; Southwest Indian Ridge; Spinel; Oxygen; chromium; fugacity; heterogeneity; igneous geochemistry; isotopic composition; mantle structure; mid-ocean ridge; mid-ocean ridge basalt; peridotite; petrography; spinel; thermodynamics; trace element; Indian Ocean; Southwest Indian Ridge
语种	英语
来源期刊	Earth and Planetary Science Letters
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/203035
作者单位	Division of Natural Sciences, Nursing, and Mathematics, Berea College, CPO 2191, Berea, KY 40404, United States; National Museum of Natural History, Smithsonian Institution, Washington, DC, 20560, United States; Department of Earth Sciences, University of Delaware, Penny Hall, Newark, DE 19716, United States; Graduate School of Oceanography, University of Rhode Island, Narragansett, RI 02882, United States; Department of Earth and Environmental Sciences, University of Minnesota Duluth, 229 Heller Hall, 1114 Kirby Drive, Duluth, MN 55812, United States
推荐引用方式 GB/T 7714	Birner S.K.,Cottrell E.,Warren J.M.,et al. Melt addition to mid-ocean ridge peridotites increases spinel Cr# with no significant effect on recorded oxygen fugacity[J],2021,566.
APA	Birner S.K.,Cottrell E.,Warren J.M.,Kelley K.A.,&Davis F.A..(2021).Melt addition to mid-ocean ridge peridotites increases spinel Cr# with no significant effect on recorded oxygen fugacity.Earth and Planetary Science Letters,566.
MLA	Birner S.K.,et al."Melt addition to mid-ocean ridge peridotites increases spinel Cr# with no significant effect on recorded oxygen fugacity".Earth and Planetary Science Letters 566(2021).