Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (32) Citing Articles via Google Scholar Google Scholar Articles by Xia, L.-Q. Articles by Wang, L.-S. Search for Related Content GeoRef GeoRef Citation

Petrogenesis of Carboniferous rift-related volcanic rocks in the Tianshan, northwestern China

Lin-Qi Xia^,1, Xue-Yi Xu^,1, Zu-Chun Xia^,1, Xiang-Min Li^,1, Zhong-Pin Ma^,1 and Li-She Wang^,1

¹ Xi'an Institute of Geology and Mineral Resources, Ministry of Land and Resources, Xi'an, Shaanxi 710054, China

The Tianshan Carboniferous rift-related volcanic rocks make up a large igneous province in northwestern China. On the basis of petrogeochemical data, the rift- related basic lavas can be classified into two major magma types. These are (1) a low-Ti/Y type situated in central and eastern Tianshan that exhibits low Ti/Y (<500), Ce/Y (<3), and SiO₂ (43–55 wt%) and relatively high Fe₂O₃^T (Fe₂O₃ as total Fe; 6.4–11.5 wt%); and (2) a high-Ti/Y type situated in western Tianshan that has high Ti/Y (>500), Ce/Y (>3), and SiO₂ (49–55 wt%) and relatively low Fe₂O₃^T (5.8–7.8 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 Tianshan Carboniferous basic lavas most likely originated from an asthenospheric oceanic-island-basalt–like mantle source (⁸⁷Sr/⁸⁶Sr_(t) 0.703–0.705, _Nd(t) +4 to +7). Crustal contamination and continental lithospheric mantle have also contributed significantly to the formation of the basic lavas of the Tianshan Carboniferous rift. Our data show that spatial petrogeochemical variations exist in the volcanic rocks of the Tianshan large igneous province. The location of the thickest volcanic succession, which has dominantly tholeiitic lavas, in the eastern Tianshan may have been centered over the melting anomaly in the mantle. The eastern Tianshan 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 Tianshan. The lower degree of partial melting in the garnet stability field of the mantle, as is characteristic of the western Tianshan basic lavas, may be the result of a relatively thicker lithosphere and lower geotherm.

Key Words: Tianshan Carboniferous rift- related volcanic rocks • geochemistry • petrogenesis • asthenosphere • lithosphere • northwest China

This article has been cited by other articles:

				Q. LI, S. LIU, Z. WANG, B. HAN, G. SHU, and T. WANG Electron microprobe monazite geochronological constraints on the Late Palaeozoic tectonothermal evolution in the Chinese Tianshan Journal of the Geological Society, March 1, 2008; 165(2): 511 - 522. [Abstract] [Full Text] [PDF]

				W.-J. Xiao, L.-C. Zhang, K.-Z. Qin, S. Sun, and J.-L. Li Paleozoic accretionary and collisional tectonics of the eastern Tianshan (China): Implications for the continental growth of central Asia Am J Sci, April 1, 2004; 304(4): 370 - 395. [Abstract] [Full Text] [PDF]