TY - JOUR

T1 - CaAl2Si2O8 polymorphs

T2 - Sensitive geothermometers and geospeedometers

AU - Gorelova, Liudmila A.

AU - Vereshchagin, Oleg S.

AU - Bocharov, Vladimir N.

AU - Krivovichev, Sergey V.

AU - Zolotarev, Andrey A.

AU - Rassomakhin, Mikhail A.

N1 - Publisher Copyright: © 2022 China University of Geosciences (Beijing) and Peking University

PY - 2023/1

Y1 - 2023/1

N2 - Plagioclase is the major rock-forming mineral constituting the Earth's crust, whereas anorthite (CaAl2Si2O8) is a common minerals in lunar highlands crust, meteorites, possibly in some comets and on Mercury. Besides anorthite, two high-temperature polymorphs of CaAl2Si2O8 are known: dmisteinbergite and svyatoslavite, which are found in burnt coal dumps, meteorites and pseudotachylytes. Here we present the results of detailed studies (quenching experiments, elemental analysis, Raman spectroscopy and in situ high temperature single crystal X-ray diffraction (up to 1000 °C)) on naturally co-occurring CaAl2Si2O8 polymorphs (anorthite, dmisteinbergite and svyatoslavite) from a burnt coal dump in Kopeisk, Russia. New polymorphs were found in all natural samples and obtained upon heating of dmisteinbergite (unquenchable β-dmisteinbergite and quenchable γ-dmisteinbergite). It was shown that Ca coordination differs significantly in CaAl2Si2O8 polymorphs, resulting in a different capacity to host Ba and possibly other large ion lithophile elements. Combining our data on natural samples with the previously published data on natural and synthetic compounds, we propose a new scheme of CaAl2Si2O8 polymorphs stability. Our results indicate that CaAl2Si2O8 polymorphs could be used for temperature estimations for both Earth and planetary sciences.

AB - Plagioclase is the major rock-forming mineral constituting the Earth's crust, whereas anorthite (CaAl2Si2O8) is a common minerals in lunar highlands crust, meteorites, possibly in some comets and on Mercury. Besides anorthite, two high-temperature polymorphs of CaAl2Si2O8 are known: dmisteinbergite and svyatoslavite, which are found in burnt coal dumps, meteorites and pseudotachylytes. Here we present the results of detailed studies (quenching experiments, elemental analysis, Raman spectroscopy and in situ high temperature single crystal X-ray diffraction (up to 1000 °C)) on naturally co-occurring CaAl2Si2O8 polymorphs (anorthite, dmisteinbergite and svyatoslavite) from a burnt coal dump in Kopeisk, Russia. New polymorphs were found in all natural samples and obtained upon heating of dmisteinbergite (unquenchable β-dmisteinbergite and quenchable γ-dmisteinbergite). It was shown that Ca coordination differs significantly in CaAl2Si2O8 polymorphs, resulting in a different capacity to host Ba and possibly other large ion lithophile elements. Combining our data on natural samples with the previously published data on natural and synthetic compounds, we propose a new scheme of CaAl2Si2O8 polymorphs stability. Our results indicate that CaAl2Si2O8 polymorphs could be used for temperature estimations for both Earth and planetary sciences.

KW - Feldspar

KW - Polymorphism

KW - Anorthite

KW - Dmisteinbergite

KW - Svyatoslavite

KW - CaAl2Si2O8

KW - Anorthite

KW - CaAl Si O

KW - Dmisteinbergite

KW - Feldspar

KW - Polymorphism

KW - Svyatoslavite

UR - http://www.scopus.com/inward/record.url?scp=85137300718&partnerID=8YFLogxK

UR - https://www.mendeley.com/catalogue/7bb3345e-ff56-3b1f-82fa-88b5c1d9b927/

U2 - 10.1016/j.gsf.2022.101458

DO - 10.1016/j.gsf.2022.101458

M3 - Article

AN - SCOPUS:85137300718

VL - 14

JO - Geoscience Frontiers

JF - Geoscience Frontiers

SN - 1674-9871

IS - 1

M1 - 101458

ER -