Zinc, copper, and strontium isotopic variability in the Baiyangping Cu–Pb–Zn–Ag polymetallic ore field, Lanping Basin, Southwest China

The Baiyangping Cu-Ag polymetallic ore district is located in the northern part of the Lanping-Simao foreland fold belt,between the Jinshajiang-Ailaoshan and Lancangjiang faults,and the deposit can be divided into eastern and western ore zones.Based upon microscope observation of ore minerals and analysis of zinc,copper,and strontium isotope composition,we conclude that:(1)the zinc isotopic compositions of sphalerite from the eastern and western ore belt of the Baiyangping polymetallic ore deposits are enriched in both the heavy(-0.09‰ to+0.15‰) and light(-0.19‰ to-0.01‰)zinc isotopes.Rayleigh fractionation is likely the additional factor controlling the observed temporal and spatial variations in zinc isotopes in the two studied ore zones.The zinc isotopic composition in the Baiyangping polymetallic Pb-Zn deposits may have the same fractionation as that of magmatic-hydrothermal,VHMS,SEDEX,and MVT deposits,as demonstrated by geological and other geochemical evidence;(2) the range of δ^(65)Cu in massive tetrahedrite is from-0.06‰ to+0.12 ‰ that relates to the early stages of ore-formation,which are higher than that of venial chalcopyrite(from-0.72‰ to-0.07‰)formed at a late ore-forming stage in the western ore belt.Different ore-forming stages and alteration or leaching processes are likely the main factors controlling the observed variations in copper isotopes in the western ore zone;(3) the ^(87)Sr/^(86)Sr value of hydrothermal calcite in eastern(0.7080-0.7093) and western(0.7085-0.7113) ore belt suggested that mineralization of early calcite,with^(87)Sr/^(86)Sr values much higher than in ancient Late Triassic seawater,may be related to recrystallization from a radiogenic Sr-rich or silicifying fluid,either from the strata that the ore-forming fluid flows through or from other fluids.

U-Pb Zircon Age, Geochemical and Sr-Nd Isotopic Constraints on the Age and Origin of the Granodiorites in Guilong, Southeastern Yunnan Province, Southern China

Post-collision felsic rocks in Southeastern Yunnan province contain granodiorites. U-Pb zircon ages, geochemical data and Sr-Nd isotopic data for these rocks are reported in the present paper. Laser ablation inductively coupled plasma mass spectrometry U-Pb zircon analyses yielded consistent age 252.5 ± 1.0 Ma for one sample of the felsic rocks. The granodiorites were characterized by variational and high (87Sr/86Sr)i, ranging from 0.7223 to 0.7236 and very low εNd (t) values from –29.1 to –30.4. In addition, these rocks are characterized by slight Eu negative anomalies, Nb, Ta, Ti and Sr negative anomalies on primitive mantle normalization spider. Geochemical and isotopic characteristics suggest that these rocks were derived from an enriched crust source. The granodiorites resulted from the fractionation of potassium feldspar, plagioclase and ilmenite or rutile. However, the granodiorites were unaffected by visible crustal contamination during ascent. As a result, the granodiorites may have been formed due to partial melting of crust-derived sedimentary rocks beneath southeastern Yunnan province, southern China.

Mineral Resource Science in China:Review and perspective

Mineral resources are essential to prosperity and security of modern societies.How mineral resources can guar-antee sustainable development of economy in countries,especially those developing countries,has long been a focus of attention of international communities.This paper provides a comprehensive summary for major ad-vance of the research on mineral resources in past decades,and proposes some key issues regarding ore-forming mechanism,exploration and utilization of major and critical mineral resources.On the basis of these aspects,we also identify four priority science issues to be addressed in the future,including(1)mechanism of both metal circulation and extremely high concentration,(2)theories and technologies of prospecting deep-earth resources,(3)investigation of mineral resources in seafloor and polar regions,and(4)efficient,clean and recycling utiliza-tion of mineral resources.It can be expected that new advances in these four issues would tremendously promote the innovation of mineral resource science,and provide scientific and technologic support to meet the demand of mineral resources for human activities and the harmonious development of both mineral-resource exploration and ecological restoration.

Zircon U-Pb Ages and Sr-Nd-Hf Isotopic Characteristics of the Huichizi Granitic Complex in the North Qinling Orogenic Belt and Their Geological Significance

The Huichizi granite complex is the largest Paleozoic 1-type intrusion located in the North Qinling orogenic belt （NQB）. In this study, we present systematic geochemical element data, zircon U-Pb ages, Ln-Hf isotopic data, and Sr-Nd isotopic data for the Huichizi granites. In terms of mineral and chemical compositions, these granites are biotite monzonitic and alkali-feldspar granites, both of which are characterized by high SiO2 and total alkali contents and low MgO, TiO2, and TFeO contents. These granites are weakly peraluminous （A/CNK values are 1-1.06 for biotite mon- zonitic granites and 1.04-1.09 for alkali-feldspar granites） and possess the geochemical characteristics of adakitic rocks, e.g., high Sr contents （319 ppm-633 ppm）, Sr/Y ratios （18.5-174）, and （La/Yb）N ratios （17.6-57） and low MgO （0.04 wt.%-0.83 wt.%）, Y （3.0 ppm-17.2 ppm）, and heavy rare-earth element （HREE） contents. This indicates that these rocks were most likely derived from the partial melting of a thickened lower crust. In situ zircon U-Pb dating of these granites yields Early Caledonian ages （437 Ma for biotite monzonitic granites and 424 Ma for alkali-feldspar granites）, indicating that the Huichizi granitic complex is the product of multi-periodic magmatism. The positive but varying zircon tHe（t） values （＋0.6 to ＋8.5） suggest that this thickened lower crust was mainly juvenile, i.e., accreted from depleted mantle during the Neo-Mesoproterozoic Period, but involved the ancient recycled crust. Biotite monzonitic granites formed during crust thickening at the extrusion stage, whereas the alkali granites formed during crust thickening at the extension stage （post extrusion）. The Huichizi granite complex witnessed the process of extrusion to extension because of the collision between the NCB and the Qinling microcontinent in the Caledonian.

扬子地块西南部关键金属元素成矿作用

在自元古代以来的长期地质演化过程中,扬子地块西南部形成了多样化的富含In、Ge、Ga、Cd、Re、Sn、Li、Nb、REE(rare earth element)和PGE(platinum group elements)等不同种类关键金属元素的矿床类型.通过总结以往的研究,本文认为该区除晚二叠世与峨眉山地幔柱活动有关的Cu-Ni-PGE岩浆硫化物矿床和新生代与印-亚大陆后碰撞造山作用有关的碳酸岩型REE矿床外,富含关键金属元素矿床的成矿作用主要显示四大特点:(1)古-中元古代发育我国首个被确认的富稀土IOCG成矿省;(2)燕山晚期与花岗岩有关的富In锡石硫化物矿床在面积很小的区域大爆发成矿;(3)印支期和燕山早期花岗岩浆活动微弱,富Ge低温Pb-Zn矿床和低温Au-As-Sb-Hg-Tl矿床广泛发育;(4)埃迪卡拉纪以来的海相沉积岩尤其是黑色页岩和碳酸盐岩广布,多时代富Li、Nb、Zr、Ga、Re、REE、PGE等的沉积和/或风化-沉积矿床大面积分布.在此基础上,进一步总结了区域地质事件与成矿事件的相互关系,提出了一些重要成矿系统值得进一步探索的领域.

Timing of Uranium Mineralization and Geological Implications of Shazijiang Granite-Hosted Uranium Deposit in Guangxi, South China: New Constraint from Chemical U-Pb Age

Miaoershan（MES） uranium ore field is one of the most important uranium sources in China, hosts the largest Chanziping carbonaceous-siliceous-pelitic rock type uranium deposit in South China together with many other granite-hosted uranium deposits. The Shazijiang（SZJ） uranium deposit is one of the representative granite-hosted uranium deposits in the MES uranium ore field, situated in the Ziyuan, Guangxi Province, South China. Uranium mineralization in the SZJ deposit mainly occurs as uraninite with quartz and calcite veins that is spatially associated with mafic dykes in the region. The hydrothermal alteration includes silicification, carbonation and hematitization. New uraninite chemical U-Pb geochronology and petrographic evidences provide the timing constraints and new insights into the formation of the SZJ uranium deposit. The results show that the first stage of uranium mineralization formed at 97.5±4.0 Ma, whereas another stage of uranium mineralization occurred at 70.2±1.6 Ma. Two stages of uranium mineralization are fairly consistent with two episodic crustal extensions that occurred at -100 and -70 Ma throughout South China. This study indicates that there are two uranium mineralization events in SZJ uranium ore field controlled by mafic dyke, supporting that mafic dykes play an important topochemical role in uranium concentration and/or mobilization. Therefore, geochemical U-Pb age firstly reinforces that ore-forming age of the SZJ uranium deposit mainly yields at 97.5±4.0 and 70.2±1.6 Ma. Additionally, geochemical age method is particularly useful for interest samples which record information on multi-stage uranium mineralizations in South China.

On emplacement ages of lam-proites in Zhenyuan County,Guizhou Province,China

Emplacement ages of lamproites that comprise lamproite and olivine lamproite in Zhenyuan County, Guizhou Province, China, have been constrained by the whole-rock Sm-Nd and Rb-Sr isochron methods and the whole rock K-Ar method. Intrusive activities of lamproites in the Sinantang area of Zhenyuan County, Guizhou Province, took place during the Late Cambrian, as indicated by the Sm-Nd isochron ages (t) = (503±17) (2σ) Ma and by the Rb-Sr isochron ages (t) = (501.2±4.6) (2σ) Ma. Intrusive activities of olivine lamproites at the Maping with Ⅱ -type diamond and Xitou in Zhenyuan County, Guizhou Province, took place from the Late Cambrian to the Early Ordovician, as evidenced by the Sm-Nd isochron ages (t) = (502±27) (2σ) Ma and by the Rb-Sr isochron age (t) = (502± 27) (2σ) Ma. This suggests that the upwelling hot materials derived from the deep mantle were emplaced from the Late Cambrian to the Early Ordovician (503-497 Ma), while the time terminal of cooling of the geothermal event of

Mercury isotope constraints on the genesis of late Mesozoic Sb deposits in South China

The late Mesozoic antimony(Sb)mineralization belt in South China hosts a large portion of the world’s Sb reserves.However,the source and mineralization processes of these Sb deposits remain controversial.Here,we measured mercury(Hg)concentrations and isotopic compositions of stibnite in the Banpo Sb-only and Woxi Sbpolymetallic ore deposits,as well as associated rocks in the Yangtze Block in order to constrain the metal sources and ore formation processes in the South China Sb mineralization belt.Stibnite samples from both deposits exhibit significant enrichment in Hg(4.23–50.6 ppm)and have higher δ^(202)Hg values(−0.47‰to 2.03‰)than the studied Precambrian basement rocks(−1.42‰to 0.59‰),Paleozoic sedimentary rocks(−2.40‰to−0.32‰),and other natural Hg reserves(e.g.,marine and continental systems).This indicates that significant mass-dependent fractionation of Hg isotopes occurred during hydrothermal processes.Negative to slightly positive Δ^(199)Hg values of−0.17‰to 0.02‰were obtained for stibnite from the studied deposits,similar to values for the Precambrian basement rocks,but different from those of the Paleozoic sedimentary rocks and data previously reported for mantle materials.This suggests that Precambrian basement rocks were the source of Hg and associated metals.Our data and the tectonic evolution of South China indicate that late Mesozoic asthenospheric upwelling,in response to the Paleo-Pacific oceanic slab foundering,generated heat that drove the circulation of fluids in the basement and crustal basinal rocks.These fluids leached Sb,Hg,and other metals from the Precambrian basement rocks and formed the world-class Sb mineralization belt in South China.

Analysis of rare-earth elements in fluid inclusions by inductively coupled plasma-mass spectrometry (ICP-MS)

Inductively coupled plasma_mass spectrometry (ICP_MS) is used to determine rare_earth elements abundances in fluid inclusions. Quartz separates from the Lannigou and Yata Carlin_type gold deposits, southwestern China, were prepared by the decrepitation_leach method. Leachates were analyzed by ICP_MS, using conventional sample introduction. The results demonstrate that the decrepitation_leach method, in combination with ICP_MS analysis of leachates, is effective for REE determination. The chondrite_normalized REE patterns of inclusion fluids for the Lannigou and Yata samples associated with gold mineralization are characterized by light rare_earth elements (LREE) enrichment, with a weak negative Ce anomaly and a positive or negative Eu anomaly, whereas the pattern for the Lannigou sample associated with late gold mineralization (quartz_calcite stage) is characterized by LREE enrichment relative to HREE, with negative Ce and Eu anomalies.

Helium isotope compositions of Machangqing copper deposit in western Yunnan, China

Helium isotopic composition of inclusion fluid in pyrites from Machangqing copper deposit, China, has been measured. The measurements, with 3He/ 4He ratios ranging from 0 46-2 08 Ra, indicate that the helium in ore_forming fluid is a mixture of crust and mantle, and are consistent with the fact that the parental magma responsible for the formation of ore_forming fluid of the deposit is of crust_mantle provenance.