首页|Munabulake ophiolitic mélange:Implication for the evolution history of the north branch of the Proto-Tethys ocean
Munabulake ophiolitic mélange:Implication for the evolution history of the north branch of the Proto-Tethys ocean
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One of the ophiolites that record the Proto-Tethys Ocean's episodic closure is the Munabulake ophiolitic mélange,which is situated in the middle of the Kunlun-Qaidam and Altun-Qilian blocks.Detailed field mapping revealed that the Munabulake ophiolitic mélange comprises local(ultramafic rocks,basalts,andesites,gabbros,diorites,and plagiogranites)and exotic(marble,gneiss,schist,and amphibolite)blocks,many of which are in the schist matrix(Qimantage Group).Based on geochronological,geochem-ical,and petrological observations,the mafic rocks in the Munabulake ophiolitic mélange can be catego-rized into three categories:498-Ma OIB-like gabbros,468-Ma Hawaiian alkaline basalt-like dolerite and pillow basaltic slices,and 428 Ma massive SSZ-like ultramafic rocks.The 501-452 Ma I-type granites exhibit arc affinities due to the oceanic crust subduction.These findings,along with spatial relationships,suggest that the Early Paleozoic ophiolite complex,island arc rocks,and accretionary complex generated as an intra-oceanic arc system as a result of obduction of the south Altun Ocean's onto the Central Altun block within a north-directed subduction event.A dextral strike-slip was evident throughout the Early Paleozoic oceanic crust subduction based on the whole set of planar and linear structural data,and the subduction polarity was likely to the north.According to the ophiolitic mélange's youngest rocks and the existence of 413 Ma granite dykes that are widely exposed in the Munabulake ophiolitic mélange,the Munabulake ophiolitic mélange was most likely emplaced during the Middle Silurian.This Munabulake ophiolitic mélange is similar in age and petrochemical characteristics to the other ophiolites in the South Altun subduction-collision belt,indicating that the Manabulak ophiolite mélange is a west-ward extension of the Apa-Mangya subduction-collision belt,which formed during the northward sub-duction of the South Altun Ocean slab during the Early Paleozoic.Thus,the final closing time of the South Altun Ocean is between 413 and 428 Ma.
China University of Geosciences(Beijing),Beijing 100083,China
Experimental School of Beijing Ritan High School,Beijing 100123,China
The Key Laboratory of Orogenic Belts and Crustal Evolution,Ministry of Education,School of Earth and Space Sciences,Peking University,Beijing 100871,China
国家自然科学基金China Geological SurveyInstitute of Geological Survey,China University of Geosciences(Beijing)
NETL
NSTL
万方数据
维普
