Origin and evolution of ore-forming fluid for the Gaosongshan gold deposit, Lesser Xing’an Range:Evidence from fluid inclusions,H-O-S-Pb isotopes

Epithermal gold deposits are typical precious metal deposits related to volcanic and subvolcanic magmatism.Due to the lack of direct geological and petrographic evidences,the origin of the ore-forming fluid is deduced from the spatial diagenesis-mineralization relationship,chronological data,physicochemical characteristics of mineral fluid inclusions,mineral or rock elements and isotopic geochemical characteristics.By objectively examining this scientific problem via a geological field survey and petrographic analysis of the Gaosongshan epithermal gold deposit,we recently discovered and verified the following points:(1) Pyrite-bearing spherical quartz aggregates (PSQA) occur in the rhyolitic porphyry;(2) the mineralization is structurally dominated by WNW- and ENE-trending systems and occurs mostly in hydrothermal breccias and pyrite-quartz veins,and the ore types are mainly hematite-crusted quartz,hydrothermal breccia,massive pyrite-quartz,etc.;(3) the alteration types consist of prevalent silicification,sericitization,propylitization and carbonation,with local adularization and illitization.The ore minerals are mainly pyrite,primary hematite,native gold,and electrum,with lesser amounts of chalcopyrite,magnetite,sphalerite,and galena,indicating a characteristic epithermal low-sulfidation deposit.The ore-forming fluid may have been primarily derived from magmatic fluid exsolved from a crystallizing rhyolitic porphyry magma.Further zircon U-Pb geochronology,fluid inclusion,physicochemical and isotopic geochemical analyses revealed that (1) rhyolitic porphyry magmatism occurred at 104.6 ± 1.0 Ma,whereas the crystallization of the PSQA occurred at 100.8 ± 2.1 Ma;(2) the hydrothermal fluid of the pre-ore stage was an exsolved CO2-bearing H2O-NaCl magmatic fluid that produced inclusions mainly composed of pure vapor (PV),vapor-rich (WV) and liquid-rich (WL) inclusions with a small number of melt-(M) and solid-bearing (S) inclusions;mineralization-stage quartz contains WL and rare PV,WV and pure liquid (PL) inclusions characterized by the H2O-NaCl system with low formation temperatures and low salinities;(3) the characteristics of hydrogen,oxygen,sulfur,and lead isotopes and those of rare earth elements (REEs) provide insight into the affinity between PSQA and orebodies resulting from juvenile crust or enriched mantle.Combined with previous research on the mineralogenetic epoch (99.32 ± 0.01 Ma),we further confirm that the mineralization of the deposit occurred in the late Early Cretaceous,which coincides with the extension of the continental margin induced by subduction of the Pacific Plate beneath the Eurasian Plate.The formation of the ore deposit was proceeded by a series of magmatic and hydrothermal events,including melting of enriched juvenile crust,upwelling,the eruption and emplacement of the rhyolitic magma,the exsolution and accumulation of magmatic hydrothermal fluid,decompression,the cooling and immiscibility/boiling of the fluid,and mixing of the magmatic fluid with meteoric water,in association with water-rock interaction.

催化臭氧氧化降解水中有机污染物的研究进展

水污染是当前工业发展中亟待解决的问题之一,催化臭氧氧化降解有机污染物工艺具有绿色、高效和工艺简单的优点而被广泛应用,而其中的关键在于催化剂的选用。本研究对均相催化臭氧氧化和非均相催化臭氧氧化过程的机理进行了分析和总结,着重讨论了非均相催化臭氧氧化过程常采用的贵金属催化剂、过渡金属催化剂、碱土金属催化剂和非金属催化剂对臭氧氧化降解有机污染物的促进作用,对提高这些催化剂催化活性的方法进行了综述,总结了pH值、臭氧浓度、催化剂剂量和有机污染物浓度对催化臭氧氧化降解有机物过程的影响。指出目前催化臭氧氧化降解有机污染物过程面临的主要问题是活性组分的流失导致催化剂催化活性下降。在今后的研究中,开发和制备新型、高效、绿色、稳定的催化剂以及探究最佳工艺条件仍是研究的重点。可以通过提高催化剂的吸附能力以改善臭氧在水溶液中的传质,促进臭氧分子的分解,还可以通过不同活性组分的协同偶联有效抑制活性组分的流失,提高催化剂催化活性的同时提高催化剂的稳定性,以达到高效降解有机化合物的目的。要点:(1)分析并总结了均相/非均相催化臭氧氧化的机理。(2)总结了贵金属催化剂、过渡金属催化剂、碱土金属催化剂及非金属催化剂在催化臭氧氧化降解有机污染物方面的应用。(3)分析并总结了pH值、臭氧浓度、催化剂剂量和反应底物浓度对催化臭氧氧化过程的影响。(4)指出了未来新型催化剂的潜在的研究方向。

Geological,Fluid Inclusion,H-O-S-Pb Isotope Constraints on the Genesis of the Erdaogou Gold Deposit,Liaoning Province

The Erdaogou gold deposit is located in the conjuncture of North China Carton and Xingmeng orogenic belt.The ore-forming process of Erdaogou gold deposit is divided into three stages(ⅠtoⅢ),which are quartz-pyrite stage(stage I),quartz-polymetallic sulfide stage(stage II)and quartz-calcite stage(stage III).Two types of fluid inclusions is distinguished in the ore-forming stage,i.e.,aqueous type(W-type)and aqueous-carbonic type(C-type)inclusions.From the stageⅠtoⅢ,the homogenization temperature of fluid inclusions are respectively 334-395,214-364 and 172-272℃,with salinities of 7.72 wt.%-11.23 wt.%NaCl equiv.,0.20 wt.%-23.18 wt.%NaCl equiv.,and 0.35 wt.%to 5.25 wt.%NaCl equiv.The ore-forming fluids of the Erdaogou deposit have the characteristics of medium-low temperatures,moderate salinities and low densities.And the fluids belong to the CO,-H2O-NaCl system.The values ofδ34SV-CDT in sulphide samples at different stages(stages I to III)are between-2.2‰ to 2.3‰,indicating sulfur source from magma volatiles or subvolcanic rock leaching.The lead isotopes suggest that ore-forming metals may be derived from a mixture of lower crust and mantle materials.Oxygen and hydrogen isotope data at Erdaogou indicate that magmatic fluid and meteoric water may both be involved in the hydrothermal system.Based on the geological characteris-tics,fluid inclusion results,stable and radiogenic isotope results of Erdaogou gold deposit,we believe that the temperature decrease,fluid boiling are the key factors leading to the ore precipitation and the genetic type of Erdaogou gold deposit is low-sulfidation epithermal deposit.