TY - JOUR

T1 - Water content and deformation of the lower crust beneath the siberian craton: Evidence from granulite xenoliths

AU - Jin, Tianlong

AU - Wang, Qin

AU - Shatsky, Vladislav

AU - Liao, Yue

N1 - Funding Information: A free program, PTQuick, for major-element ther-mobarometers developed by Sergey K. Simakov and Dmitry V. Dolivo-Dobrovolsky was used for P-T estimation of granulite xenoliths. We are grateful to Y. Dilek for his invitation and encouragement to write the manuscript, to P. Kempton and two anonymous reviewers for their constructive comments, and to editor D. Rowley for his careful and thoughtful review. We thank M. Wu for her help in thin-section observations and temperature calculations and C. Wei for help in pseudosection calculations. This research was supported by the National Natural Science Foundation of China (NSFC) projects (41825006 and 41590623) and the NSFC-Russian Foundation for Basic Research Cooperative Project (no. 4141101061). Publisher Copyright: © 2021, University of Chicago Press. All rights reserved.

PY - 2021/9

Y1 - 2021/9

N2 - Water in the lower crust plays a critical role in rheological layering of the continental lithosphere. Sixteen granulite xenoliths were collected from the Late Devonian Udachnaya and Komsomolskaya kimberlites in the Siberian Craton. Mafic granulite samples experienced pressures of 0.6–1.0 GPa and temperatures of 5497–8007C using the Grt-Cpx (garnet-clinopyroxene) Fe-Mg thermometer, which are consistently lower than equilibrium temperatures of 7377– 8997C from the REE-in-Grt-Cpx thermobarometer. Compared with pseudosection calculations, our samples experienced continuous cooling since the last granulite facies metamorphism. Moderate to high water content was measured in clinopyroxene (334–977 ppm H2 O), garnet (23–149 ppm H2O), and plagioclase (157–779 ppm H2 O), resulting in the bulk water content of 267–707 ppm H2 O in granulite samples. Given the very limited later metasomatism and hydrogen loss, water content in granulite xenoliths probably represents in situ water-rich lower crust of the Siberian Craton from 1.8 Ga to the Late Devonian. Clinopyroxene and plagioclase show weak crystallographic preferred orientations, whereas garnet has random orientation. Compared with previous studies, the Precambrian lower crust in stable cratons contains comparable or less water than Phanerozoic lower crust in orogenic belts. Magma underplating in cratons can trigger partial melting of ancient water-rich granulites and produce heterogeneous water distribution in the lower crust.

AB - Water in the lower crust plays a critical role in rheological layering of the continental lithosphere. Sixteen granulite xenoliths were collected from the Late Devonian Udachnaya and Komsomolskaya kimberlites in the Siberian Craton. Mafic granulite samples experienced pressures of 0.6–1.0 GPa and temperatures of 5497–8007C using the Grt-Cpx (garnet-clinopyroxene) Fe-Mg thermometer, which are consistently lower than equilibrium temperatures of 7377– 8997C from the REE-in-Grt-Cpx thermobarometer. Compared with pseudosection calculations, our samples experienced continuous cooling since the last granulite facies metamorphism. Moderate to high water content was measured in clinopyroxene (334–977 ppm H2 O), garnet (23–149 ppm H2O), and plagioclase (157–779 ppm H2 O), resulting in the bulk water content of 267–707 ppm H2 O in granulite samples. Given the very limited later metasomatism and hydrogen loss, water content in granulite xenoliths probably represents in situ water-rich lower crust of the Siberian Craton from 1.8 Ga to the Late Devonian. Clinopyroxene and plagioclase show weak crystallographic preferred orientations, whereas garnet has random orientation. Compared with previous studies, the Precambrian lower crust in stable cratons contains comparable or less water than Phanerozoic lower crust in orogenic belts. Magma underplating in cratons can trigger partial melting of ancient water-rich granulites and produce heterogeneous water distribution in the lower crust.

UR - http://www.scopus.com/inward/record.url?scp=85117831418&partnerID=8YFLogxK

U2 - 10.1086/716514

DO - 10.1086/716514

M3 - Article

AN - SCOPUS:85117831418

VL - 129

SP - 475

EP - 498

JO - Journal of Geology

JF - Journal of Geology

SN - 0022-1376

IS - 5

ER -