NDLI: The Dongcaohe ophiolite from the North Qilian Mountains: A fossil oceanic crust of the Paleo-Qilian ocean

Content Provider	Springer Nature Link
Author	Tseng, Chien Yuan Yang, Huai Jen Yang, Houng Yi Liu, DunYi Tsai, Ching Lang Wu, HanQuan Zuo, GuoChao
Copyright Year	2007
Abstract	The Dongcaohe ophiolite, located at the south of the North Qilian subduction complexes, is a tectonic block with an exposed area of about 3 km×6 km. It consists of an intrusive section overlain by an extrusive section. The lower part of the intrusive section consists of cyclic layers of cumulate dunites, troctolites, anorthosites, anorthositic gabbros, and gabbros with small discordant dunite and troctolite bodies. This layered sequence grades upward to isotropic gabbros and gabbronorites, which are overlain by the extrusive sequence of diabasic sheeted dikes and basaltic lavas. The overall mineral crystallization sequence was olivine±Cr-spinel, plagioclase, clinopyroxene, orthopyroxene, and Fe-Ti oxides. The Cr-spinel (Mg#: 42–66, Cr#: 41–57) in these layered cumulates and present-day abyssal peridotites have similar compositions. Also, the compositional variations of the plagioclase and clinopyroxene in the intrusive section reflect crystallization from melts compositionally similar to the present-day ocean basalts. Moreover, the rare earth element (REE) and multi-element distribution patterns of the intrusive and extrusive lithologies in the Dongcaohe ophiolite are consistent with crystallization of mid-ocean ridge basalts. The zircon grains separated from the gabbronorite have an SHRIMP average $^{206}$Pb/$^{238}$U weighted age of 497 ± 7 Ma, which is considered as the tectonic emplacement age of the Dongcaohe ophiolite. The field occurrence, mineral and whole-rock compositions indicate that the Dongcaohe ophiolite represents a well-persevered oceanic crustal fragment composed of a complete oceanic crustal section of layered cumulates at bottom upgrading through isotropic cumulates to sheeted dikes and lava flows.
Starting Page	2390
Ending Page	2401
Page Count	12
File Format	PDF
ISSN	10016538
Journal	Chinese Science Bulletin
Volume Number	52
Issue Number	17
e-ISSN	18619541
Language	English
Publisher	Science in China Press
Publisher Date	2007-01-01
Publisher Place	Beijing
Access Restriction	Subscribed
Subject Keyword	ophiolite North Qilian oceanic crust Dongcaohe Science Physics Chemistry/Food Science Life Sciences Geosciences Engineering
Content Type	Text
Resource Type	Article
Subject	Multidisciplinary

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