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Compositions of Upper Mantle Fluids Beneath Eastern China: Implications for Mantle Evolution
Author(s) -
Mingjie ZHANG,
Xianbin WANG,
Gang LIU,
Tongwei ZHANG,
Wenrui BO
Publication year - 2004
Publication title -
acta geologica sinica ‐ english edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.444
H-Index - 61
eISSN - 1755-6724
pISSN - 1000-9515
DOI - 10.1111/j.1755-6724.2004.tb00683.x
Subject(s) - mantle (geology) , metasomatism , geology , craton , xenolith , geochemistry , partial melting , transition zone , basalt , olivine , petrology , tectonics , paleontology
The composition of gases trapped in olivine, orthopyroxene and clinopyroxene in lherzolite xenoliths collected from different locations in eastern China has been measured by the vacuum stepped‐heating mass spectrometry. These xenoliths are hosted in alkali basalts and considered as residues of partial melting of the upper mantle, and may contain evidence of mantle evolution. The results show that various kinds of fluid inclusions in lherzolite xenoliths have been released at distinct times, which could be related to different stages of mantle evolution. In general, primitive fluids of the upper mantle (PFUM) beneath eastern China are dominated by H 2 , CO 2 and CO, and are characterized by high contents of H 2 and reduced gases. The compositions of PFUM are highly variable and related to tectonic settings. CO, CO 2 and H 2 are the main components of the PFUM beneath cratons; the PFUM in the mantle enriched in potassic metasomatism in the northern part of northeastern China has a high content of H 2 , while CO 2 and SO 2 are the dominant components of the PFUM in the Su‐Lu‐Wan (Jiangsu‐Shandong‐Anhui) region, where recycled crustal fluids were mixed with deeper mantle components. There are several fluids with distinct compositions beneath eastern China, such as primitive fluids of upper mantle (CO, CO 2 and H 2 ), partial melting fluids (CO 2 and CO) and metasomatic fluids mixed with recycled crustal fluids (CO 2 , N 2 , SO 2 and CH 4 ) etc. Fluids of the upper mantle beneath the North China craton are different from that of the South China craton in total gases and chemical compositions: the contents of the reduced gases of the PFUM in the NCC are higher than those in the SCC.