GEOCHEMICAL CHARACTERISTICS AND GEOLOGICAL IMPLICATION OF MAFIC DIKES FROM THE WALEGA MINING AREA IN THE EASTERN SEG-MENT OF THE EAST KUNLUN OROGENIC BELT
The East Kunlun orogenic belt,located on the northeastern margin of the Tibetan Plateau,is a significant tectonic magmatic belt.However,Cenozoic magmatic activity is rare in this region.This paper examines the lithography,petrogeochemistry,and chronology of the basic dikes in the Valega mining are-a,situated in the eastern part of East Kunlun.The basic dikes in the study area are predominantly orien-ted in an east-west direction,aligning with the regional fault trends.The main rock types identified in these dikes are gabbro and diabase.Geochemical analysis of the rocks reveals characteristics of low to me-dium potassium-calc alkaline quasi-aluminum composition,with A/CNK values ranging from 0.70 to 0.79,AR values from 1.26 to 1.35,and σ values also from 1.26 to 1.35.The rocks are enriched in large ion lithophile elements(Ba,K,Rb)and relatively depleted in high field strength elements(Nb,Ta).The fractionation between light and heavy rare earth elements(REE)is minimal,with average LREE/HREE ratios of 2.92 and 2.26.The 8Eu values show no significant anomalies(ranging from 0.97 to 1.05),while 8Ce values indicate a slight positive anomaly(ranging from 1.03 to 1.07).The rare earth element compo-sition of zircons from the mafic dikes exhibits typical magmatic zircon characteristics,including a positive Ce anomaly,a negative Eu anomaly,a deficit in light REE,and enrichment in heavy REE.LA-MC-ICPMS zircon U-Pb dating results indicate that the Valga basic dikes formed in the early Miocene,with a-ges constrained to 17.31±0.26 Ma and 16.93±0.33 Ma.The geochemical characteristics suggest that the basic dikes are related to intraplate basalt formed in a tensile environment,similar to the tectonic back-ground of Cenozoic volcanic rocks in northern Tibet.From a regional tectonic perspective,it is proposed that activities along the East Kunlun strike-slip fault induced thinning and melting of the lower lithospheric enriched mantle,leading to the upwelling of this enriched mantle.The ascending melt magma migrated a-long deep faults in the East Kunlun area,mixed with lower crustal material,and eventually crystallized in the Valega area.The study of these basic dikes fills a gap in the understanding of Cenozoic magmatic activ-ity in the East Kunlun orogenic belt,providing new insights into the region's tectonic and magmatic evolu-tion.
万方数据
维普
