滇西北中甸地区红山—红牛铜钼矿复合成矿作用及成矿模式OA

Composite mineralization represents a significant metallogenic style in the Sanjiang tectonic domain.The Géza area in northwestern Yunnan has experienced multistage tectonic evolution,including Late Triassic oceanic crust subduction,Jurassic-Cretaceous collisional orogeny,and Paleogene tectonic reworking,and is characterized by prolonged and episodic tectono-magmatic activity.The Hongshan-Hongniu porphyry-skarn Cu-Mo deposit exemplifies one of the typical composite mineralization systems in this region.Whole-rock geochemical data indicate that the Indosinian intrusions are characterized by quasi-aluminous to peraluminous(A/CNK=0.30～1.18)high-K calc-alkaline granites.In contrast,the Yanshanian intrusions are enriched in silicon(SiO2=59.19%～72.20%)and alkalis(K2O+Na2O=6.65%～12.33%),with higher light to heavy rare earth element fractionation(LREEs/HREEs=18.28～24.66)compared to the Indosinian suite.These rocks are enriched in large-ion lithophile elements,exhibit negative Ba anomalies,and are relatively depleted in high-field-strength elements,collectively indicating a continental crustal origin for the Yanshanian magmatism.The Hongshan-Hongniu Cu-Mo deposit records multiple distinct episodes of magmatic intrusion:(1)emplacement of crust-mantle hybrid magmas in a subduction setting during the Indosinian(247.4 Ma±1.9 Ma～199.0 Ma±0.6 Ma),associated with the westward subduction of the Garzê-Litang oceanic crust;(2)deep crustal melting in a post-collisional extensional setting during the Late Yanshanian(84.2 Ma±3.0 Ma～72.5 Ma±6.7 Ma);and(3)activity of enriched mantle-derived magmas in an intracontinental strike-slip setting during the Himalayan(42.99 Ma±0.35 Ma～40.67 Ma±0.40 Ma).Sulfur isotope compositions of metal sulfides yield δ34S values ranging from-1.03‰ to 6.5‰,with a mean of 4.07‰,suggesting a sulfur source primarily of magmatic origin.Lead isotope ratios are characterized by 206Pb/204Pb=18.47～18.81(mean 18.67),207Pb/204Pb=15.61～15.78(mean 15.68),and 208Pb/204Pb=38.62～39.54(mean 39.12).These isotopic features indicate that the ore-forming materials were mainly derived from the emplacement of Late Yanshanian granitic magmas,likely generated primarily by partial melting of crustal sources.Zircon Hf isotopic compositions of the intrusive rocks reflect distinct magmatic source characteristics across different periods.The Indosinian intrusions exhibit relatively high εHf(t)values,indicating significant mantle-derived inputs.In contrast,the Yanshanian intrusions show negative εHf(t)values,consistent with remelting of Mesoproterozoic crustal materials.The Himalayan intrusions display values clustering near zero,suggesting crust-mantle hybridization.This secular variation records a dynamic evolution from subduction-related crust-mantle interaction through crustal remelting to intracontinental crust-mantle mixing.The Hongshan-Hongniu Cu-Mo deposit records multiphase tectono-magmatic evolution and associated metallogenic events.During the Late Triassic,quartz diorite porphyrite and quartz monzonite porphyry were emplaced,leading to skarn-type copper mineralization in the exocontact zone.These intrusions,together with Late Cretaceous quartz monzonite porphyry and deeper concealed granite porphyry,constitute a composite pluton formed by multiple magmatic pulses.Spatially and genetically linked to Cu-Mo-W mineralization,the deposit represents a typical composite genetic system.