Wenyu Copper(Silver)Deposit Ore-Forming Geological Background,Jingdong County, Yunnan:Geochronology and Geochemistry Evidences from Ore-Bearing Volcanic Rocks
Song Junlong
Ding Jun
Wang Baodi
Liu Yansong
Zhao Rongchun
Shu Yuehong
Abstract：Wenyu copper(silver)ore,located in Yun county-Jinghong volcanic arc,is important deposit related to volcanism.It is important to understand its geological background since it is basic for discussing mineralization of Wenyu ore area.This paper reports petrology,geochemistry and zircon LA-ICP-MS chronology of volcanic rocks from Xiaodingxi Formation in the mining area.Results show that they are composed of basaltic rocks and a small amount of acidic rocks,with SiO2ranging from 47.94%―54.02% and 76.92%―84.16%,respectively,exhibiting the features of bimodal volcanic rocks.Zircon U-Pb age of rhyolite is 238.4±2.4 Ma(MSWD=1.4),showing that volcanic rocks in Xiaodingxi Formation formed at Middle Triassic, rather than Late Triassic.The basaltic volcanic rocks are characterized by low Mg and high Al,belonging to shoshonite-high K calc-alkaline-calc-alkaline series,with strong negative Sr,Ti,Nb and Ta anomalies,weak negative Eu anomalies,and lower (La/Yb)Nratio and Mg#,Cr and Ni contents.Acidic volcanic rocks belong to peraluminous high K calc-alkaline series,with strong negative Sr,Ti,P,Nb,Ta,Ba and Eu anomalies.Nb/Ta and Th/Ce ratios are relatively consistent with those of conti-nental crust,displaying characteristics of high Th and low Mg#,which suggests that it formed in an extension setting during a margin of arc(continent)-continent collision in the early Middle Triassic,which is a result of oceanic crust subduction slab break-off.In combination with regional volcanism and metallogenesis research data,it is concluded that multi-stage volcanism in the collision extension environment occurred many times during the Middle Triassic,indicating a good prospect of volcanism mineralization.
Keywords：zircon U-Pb geochronologyvolcanic rockgeochemistryWenyu copper(silver)oreYunnan
Publication Date：2018-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：20( 696-715 )