Petrological Characteristics,U-Pb Age and Tectonic Environment Characteristics of the Early Paleozoic Volcanic Rocks in the Kaladawan Area of the Altun Mountains
A set of marine volcanic rocks are exposed in the Kaladawan area of Altun Mountain.Based on the volcanic rocks'structural characteristics and lithological associations,they are divided into six eruption rhythms,three eruption sub-cycles,and one volcanic eruption cycle.By conducting zircon U-Pb dating on the crystal tuff at the top and bottom of the Pb-Zn Ore bearing stratum,an age of 487.9-489.8 Ma formed during the Late Cambrian-Early Ordovician(∈3-O1)was obtained.The volcanic rocks related to the Pb-Zn deposit are mainly the high potassium calc alkali dacite,rhyolite,etc.It has apparent relative depletion of Nb,Ta,Sr,Hf,Y,and relative enrichment of Ba,Th,Zr,and U,and has trace ele-ment geochemical characteristics of calc-alkaline volcanic rocks formed in subduction zone environments characterized by light rare earth enrichment and extreme Eu depletion.Combined with previous research results,we speculate that the tectonic environment belongs to the spreading back-arc basin.
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