气候变化领域集成服务门户(CCPortal): Origins of Major Element, Trace Element, and Isotope Garnet Signatures in Mid-Ocean Ridge Basalts

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DOI	10.1029/2020JB019612
	Origins of Major Element, Trace Element, and Isotope Garnet Signatures in Mid-Ocean Ridge Basalts
	Krein S.B.; Behn M.D.; Grove T.L.
发表日期	2020
ISSN	21699313
卷号	125 期号:12
英文摘要	To investigate whether the source of the globally occurring garnet signature in mid-ocean ridge basalt (MORB) is “true” (imparted by melting a garnet-bearing source) or “apparent” (produced without the involvement of garnet), we present the basalt petrogenesis model Petrogen. Petrogen is built on Kinzler and Grove (1992a, https://doi.org/10.1029/91JB02841) and Behn and Grove (2015, https://doi.org/10.1002/2015JB011885) and calculates the major element, trace element, and isotopic compositions of primary lherzolite-saturated mantle melts and their subsequent evolution to eruption. This model is experimentally calibrated for melting in the plagioclase, spinel, and garnet fields with and without small amounts of water. Petrogen predicts that garnet-lherzolite melting requires small mantle porosity (ϕ = ∼0.1%) and enriched (NaK# > 0.1), hot (>1400–1450°C), and damp mantle (>350–700 ppm water) sources. When garnet-lherzolite melting does occur, the fraction of melting that takes place in the garnet field is not sufficient to impart a recognizable true garnet signature in the major and trace element composition of pooled melts except at ultraslow-spreading rates (half rate ≤ 0.5 cm/yr). Therefore, for ambiguous garnet trace element signatures in MORB to be “true” would require that they are near-fractional garnet-lherzolite melts or garnet-pyroxenite melts diluted by mixing in random proportions. While we do not test the process of random mixing, we find that near-fractional and pooled melts of variable major and trace element mantle peridotite compositions at different mantle potential temperatures can explain the range of garnet signatures in MORB. For spinel-peridotite melting to support garnet signatures requires mantle porosities ϕ = ∼0.1%; however, plagioclase-peridotite melting, under specific circumstances, can explain MORB garnet signatures with ϕ = ∼1%. ©2020. American Geophysical Union. All Rights Reserved.
英文关键词	garnet melting; garnet signatures; major and trace elements; mantle melting; MORB; U-series
语种	英语
来源期刊	Journal of Geophysical Research: Solid Earth
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/187458
作者单位	Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, United States; Department of Earth and Environmental Sciences, Boston College, Chestnut Hill, MA, United States
推荐引用方式 GB/T 7714	Krein S.B.,Behn M.D.,Grove T.L.. Origins of Major Element, Trace Element, and Isotope Garnet Signatures in Mid-Ocean Ridge Basalts[J],2020,125(12).
APA	Krein S.B.,Behn M.D.,&Grove T.L..(2020).Origins of Major Element, Trace Element, and Isotope Garnet Signatures in Mid-Ocean Ridge Basalts.Journal of Geophysical Research: Solid Earth,125(12).
MLA	Krein S.B.,et al."Origins of Major Element, Trace Element, and Isotope Garnet Signatures in Mid-Ocean Ridge Basalts".Journal of Geophysical Research: Solid Earth 125.12(2020).