Geochemical implication of Eu isotopic ratio in anorthosite: new evidence of Eu isotope fractionation during feldspar crystallization.

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Bibliographic Details
Title:	Geochemical implication of Eu isotopic ratio in anorthosite: new evidence of Eu isotope fractionation during feldspar crystallization.
Authors:	Lee, Seung-Gu¹ (AUTHOR) sgl@kigam.re.kr, Tanaka, Tsuyoshi² (AUTHOR), Lee, Mi Jung³ (AUTHOR)
Source:	Geosciences Journal. Jun2023, Vol. 27 Issue 3, p271-284. 14p.
Subject Terms:	Isotopic fractionation, Anorthosite, Rare earth metals, Feldspar, Igneous rocks, Geochemistry
Abstract:	Rare earth element geochemistry (REE) can provide critical information on the evolution of the crust-mantle system. Europium (Eu) exists in divalent and trivalent states, and Eu2+ can substitute for Ca2+ during plagioclase feldspar crystallization in reducing magmas. This leads to positive Eu anomaly in Ca-plagioclase-rich anorthosite derived from the mantle and negative Eu anomalies in fractionated silica-rich crustal rocks. While many studies have addressed Eu anomalies in REE data, especially in igneous rocks, almost none have evaluated ratios of Eu's two stable isotopes (151Eu and 153Eu) alongside Eu anomalies. Here we report systematic variation of the Eu isotopic ratio (δ153Eu) from igneous rocks including anorthosite. This study detected a correlation between Eu anomalies and Eu isotopic ratios. Rhyolites and highly fractionated granites exhibited large negative Eu anomalies and negative δ153Eu values while anorthosites exhibited large positive Eu anomalies and positive δ153Eu values. In the case of the highly fractionated igneous rocks with negative Eu anomaly, the Eu isotope fractionation slope varied according to the degree of magmatic differentiation for both volcanic (extrusive) and plutonic (intrusive) rocks. Our finding reveals that Eu isotope fractionation in igneous rocks can provide new information related to magmatic differentiation and plagioclase feldspar crystallization including anorthosite formation. [ABSTRACT FROM AUTHOR]
Database:	Energy & Power Source

Description
Abstract:	Rare earth element geochemistry (REE) can provide critical information on the evolution of the crust-mantle system. Europium (Eu) exists in divalent and trivalent states, and Eu2+ can substitute for Ca2+ during plagioclase feldspar crystallization in reducing magmas. This leads to positive Eu anomaly in Ca-plagioclase-rich anorthosite derived from the mantle and negative Eu anomalies in fractionated silica-rich crustal rocks. While many studies have addressed Eu anomalies in REE data, especially in igneous rocks, almost none have evaluated ratios of Eu's two stable isotopes (151Eu and 153Eu) alongside Eu anomalies. Here we report systematic variation of the Eu isotopic ratio (δ153Eu) from igneous rocks including anorthosite. This study detected a correlation between Eu anomalies and Eu isotopic ratios. Rhyolites and highly fractionated granites exhibited large negative Eu anomalies and negative δ153Eu values while anorthosites exhibited large positive Eu anomalies and positive δ153Eu values. In the case of the highly fractionated igneous rocks with negative Eu anomaly, the Eu isotope fractionation slope varied according to the degree of magmatic differentiation for both volcanic (extrusive) and plutonic (intrusive) rocks. Our finding reveals that Eu isotope fractionation in igneous rocks can provide new information related to magmatic differentiation and plagioclase feldspar crystallization including anorthosite formation. [ABSTRACT FROM AUTHOR]
ISSN:	12264806
DOI:	10.1007/s12303-023-0009-6