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Geochemistry of Two Types of Basalts in the Emeishan Basaltic Province: Evidence for Mantle Plume‐Lithosphere Interaction
Author(s) -
Zhaochong ZHANG,
Fusheng WANG
Publication year - 2002
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.1755-6724.2002.tb00088.x
Subject(s) - basalt , geology , geochemistry , mantle plume , mantle (geology) , lithosphere , igneous rock , crust , incompatible element , partial melting , plume , trachyte , large igneous province , continental crust , petrology , volcanic rock , volcano , tectonics , magmatism , paleontology , physics , thermodynamics
Abstract Based on the temporal‐spatial distribution and geochemical characteristics, the Emeishan basalts can be divided into two types: high‐P 2 O‐TiO 2 basalt (HPT) and low‐P 2 O 5 ‐TiO 2 basalt (LPT), which differ distinctly in geochemistry: the LPTs are characterized by relatively high abundances of MgO, total FeO and P 2 O 5 and compatible elements (Cr, Ni, Sc), and relatively low contents of moderately compatible elements (V, Y, Yb, Co), LREE and other incompatible elements compared with the HPT. On the diagrams of trace element ratios, they are plotted on an approximately linear mixing line between depleted and enriched mantle sources, suggesting that these two types of basalts resulted from interactions of varying degrees between mantle plume and lithospheric mantle containing such volatile‐rich minerals as amphibole and apatite. The source region of the LPT involves a smaller proportion of lithospheric components, while that of the HTP has a larger proportion of lithospheric components. Trachyte is generated by partial melting of the basic igneous rocks at the base of the lower continental crust. Both the two types of magmas underwent certain crystal fractionation and contamination of the lower crust at high‐level magma chambers and en route to the surface.