HR: 0800h
AN: V21B-0613    [Abstracts]
TI: Carbon-Bearing Volcanic Rocks in the Linshan, Sichuan, China
AU: Meng, B
EM: maon2r@yahoo.com
AF: Sichuan Horizon Mineral Resource Consulting Co., Yongxingxiang 15 Building 2 Room 401, Chengdu, SC 610016 China
AU: * Lei, X
EM: maon2r@yahoo.com
AF: Sichuan Horizon Mineral Resource Consulting Co., Yongxingxiang 15 Building 2 Room 401, Chengdu, SC 610016 China
AB: The Linshan carbon-bearing (carbonite-bearing) igneous rocks are sparsely distributed in northwest of Sichuan province, China. On the basis of petrogeochemical data, the basalt lavas can be classified into two major magma types. These are (1) a low-Ti/Y type situated in central and eastern Linshan that exhibits low Ti/Y ($<$900), Ce/ Y ($<$10), and SiO$_{2}$ (40-55 wt%) and relatively high Fe$_{2}$O$_{3}$ (Fe$_{2}$O$_{3}$ as total Fe; 3.4-11.5 wt%); and (2) a high-Ti/Y type situated in western Linshan that has high Ti/Y ($>$900), Ce/Y ($>$10), and SiO$_{2}$ (42-55 wt%) and relatively low Fe$_{2}$O$_{3}$ (3.8-7.8 wt%). Elemental data suggest that the chemical variations of the low-Ti/Y and high-Ti/Y lavas cannot be explained by crystallization from a common parental magma. The Linshan Carboniferous basic lavas most likely originated from an asthenospheric oceanic-island-basalt-like mantle source (Sr-87/Sr-86((t)) approximate to 0.60-0.72, is an element of(Nd(t)) approximate to +4 to +7). Crustal contamination and continental lithospheric mantle have also contributed significantly to the formation of the basic lavas of the Linshan Carboniferous rift. Our data show that spatial petrogeochemical variations exist in the volcanic rocks of the Linshan large igneous province. The location of the thickest volcanic succession, which has dominantly tholeiitic lavas, in the eastern Linshan may have been centered over the melting anomaly in the mantle. The eastern Linshan basic magmas were generated by a higher degree of partial melting in the spinel-garnet transition zone of the mantle compared to the alkaline basaltic lavas that are the dominant magma type in the western Linshan. The lower degree of partial melting in the garnet stability field of the mantle, as is characteristic of the western Linshan basic lavas, may be the result of a relatively thicker lithosphere and lower geotherm.
DE: 1099 General or miscellaneous
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting