Age and tectonic setting of the first orogenic gold deposit discovered in the Yanbian Region,NE China

The Yangjingou gold deposit in Jilin Province lies 11 km south of the large-scale Xiaoxinancha gold–copper deposit. Yangjingou orebodies are structurally controlled fault- or fracture-related auriferous quartz veins. This type of mineralization is significantly different from that of the Xiaoxinancha porphyry gold–copper deposit, and has mineral assemblages and fluid inclusion compositions typical of orogenic gold deposits. We suggest that the Yangjingou deposit is the first orogenic gold deposit discovered in the Yanbian area, even in all of NE China. Here, we present new isotopic dating and trace element analysis of the ore-hosting monzogranite and auriferous quartz veins within the deposit, in order to determine the age and tectonic setting of metallogenesis, and the geological conditions controlling gold mineralization. LA-ICP-MS U–Pb dating of zircons separated from the monzogranite yielded an age of 262.3 ± 1.3 Ma, indicating intrusion during the late Permian. Hydrothermal muscovite from auriferous quartz veins yielded a ⁴⁰Ar/³⁹Ar plateau age of 241.57 ± 1.2 Ma, indicating that gold mineralization occurred at 241 Ma. Trace element and REE compositions of the monzogranite and auriferous quartz veins are both indicative of the formation from a region of the upper mantle that previously underwent crustal contamination. Geochronological analysis indicates that the diagenesis and mineralization resulting in the Yangjingou gold deposit occurred during the late Permian–Early Triassic. The tectonic evolution of the region and comparison of this deposit with other mineralizing events indicate that the orebody formed during orogenesis associated with collision between the North China and Siberian cratons.     

The Zaderzhninskoe gold deposit: Mineral composition,fluid inclusions,and age (South Verkhoyansk region)

Based on results of study of the regional position, chemical composition of ores, fluid inclusions, and age relationships between mineralization and igneous rocks, we propose a geological and genetic model for the formation of gold mineralization of the Zaderzhninskoe deposit. Mineralization is located in the tectonic node of the intersection of two regional structures in the supraintrusive zone of a latent granitoid pluton among the terrigenous rocks of the Verkhoyansk complex, which are regionally metamorphosed to the greenschist facies. The sequential deposition of three types of mineralization—Au-quartz (including early low-gold Au-As and late productive Au-Pb-Zn mineralization), Au-rare-metal, and Au-silver—has been established. The Au-Bi (Te) assemblage contains native bismuth, bismuthinite, hedleyite, Bi sulfotellurides, gustavite group minerals, and secondary minerals—Bi oxides and Bi tellurites with low-grade gold. Hg-containing electrum and kustelite, Ag-Sb and Ag-Pb-Sb sulfosalts, stutzite, Te-Pb-containing canfieldite, freibergite, and Au and Ag sulfides are indicator minerals of the Au-Ag (Sb) assemblage. Ore formation occurred at temperatures from 90 to 340 °C, with the participation of lowly and moderately concentrated solutions with CO₂ ± CH₄ ± N₂ gas phase. A decrease in temperature from Au-quartz mineralization (200-220 °C) to the late epithermal one (160 °C) and a slight increase in the concentration of solutions (up to 10 wt.% NaCl equiv.) have been established. The deposit resulted from the intricate multistage geodynamic evolution of the South Verkhoyansk region. Ore-forming processes are associated with the evolution of magmatic objects. Dating of igneous rocks yields the following ages: diorites—130-137 Ma (Rb-Sr), spessartites—126 ± 3 Ma (Rb-Sr), and kersantites—115 ± 1.7 Ma (Ar/Ar). Early concordant Au-quartz (Au-As) mineralization of the deposit is comparable with metamorphic-related Au-quartz veins of the Yur-Bular type, and its age is taken as > 137 Ma. The time of formation of Au-quartz (Au-Pb-Zn) mineralization is estimated at 123.5 ± 1.6 Ma (Ar/Ar) and is coeval with the time of intrusion of the Early Cretaceous granitoids of the South Verkhoyansk region. The imposed low-temperature mineralization undoubtedly has a younger age. Its formation was followed by the successive deposition of Au-rare-metal mineralization at the final stage of formation of granitoid plutons (~ 120 Ma) and Au-Ag mineralization in the period 100 ± 5 Ma, i.e., the time of formation of late-stage granodiorite-granite intrusions.     

Timing and Processes of Ore Formation in the Qingchengzi Polymetallic Orefield, Northeast China: Evidence from 40Ar/39Ar Geochronology

The Qingchengzi orefield is a large polymetallic ore concentration area in the Liaodong peninsula,northeastern China,that includes twelve Pb-Zn deposits and five Au-Ag deposits along its periphery.The ore-forming age remains much disputed,which prevents the identification of the relationship between the mineralization and the associated magmatism.In this paper,we quantitatively present the feasibility of making ore mineral ~(40)Ar/~(39)Ar dating and report reliable ~(40)Ar/~(39)Ar ages of lamprophyre groundmass,K-feldspar and sphalerite from the Zhenzigou deposit.Direct and indirect methods are applied to constrain the timing of mineralization,which plays a vital role in discussing the contribution of multistage magmatism to ore formation.The low-potassium sphalerite yielded an inverse isochron age of 232.8±41.5 Ma,which features a relatively large uncertainty.Two lamprophyre groundmasses got reliable inverse isochron ages of 193.2±1.3 Ma and 152.3±1.5 Ma,respectively.K-feldspar yielded a precise inverse isochron age of 134.9±0.9 Ma.These four ages indicate that the mineralization is closely associated with Mesozoic magmatism.Consequently,regarding the cooling age of the earliest Mesozoic Shuangdinggou intrusion(224.2±1.2 Ma)as the initial time of mineralization,we can further constrain the age of the sphalerite to 224–191 Ma.These new and existing geochronological data,combined with the interaction cutting or symbiotic relationship between the lamprophyre veins and ore veins,suggest that the Pb-Zn-Au-Ag mineralization in the Qingchengzi orefield mainly occurred during three periods:the late Triassic(ca.224–193 Ma),the late Jurassic(ca.167–152 Ma)and the early Cretaceous(ca.138–134 Ma).This polymetallic deposits are shown to have been formed during multiple events coinciding with periods of the Mesozoic magmatic activity.In contrast,the Proterozoic magmatism and submarine exhalative and hydrothermal sedimentation in the Liaolaomo paleorift served mainly to transport and concentrate the ore-forming substances at the Liaohe Group with no associated Pb-Zn-Au-Ag mineralization.     

Dating Magmatic Hornblende and Biotite and Hydrothermal Sericite by Laser Probe Technique：Constraints on Genesis of Wangershan Gold Deposit, Eastern Shandong Province, China

INTRODUCTIONEasternShandongProvincerepresentsthelargestgoldconcentrationregioninChina ,withannualproduc tion >5 5 - 6 0tgoldandpresentreserveofmorethan90 0tgold ,accountingforaquarterofthetotalgoldproductioninthecountry .Amajorityofthegoldde positsishostedintheJurassic Cretaceousgranitoidin trusions .TimingofgoldmineralizationineasternShan donghasbeenamajorfocusofmanypreviousstudies .K Ar,Rb SrandconventionalU Pbisotopicdatinginthelasttwodecadeshaveyieldedawiderangeofminer alizationag…     

Rb–Sr Dating of Gold‐bearing Pyrites from Wulaga Gold Deposit and its Geological Significance

Wulaga epithermal gold deposit is located in northeast China. Gold mineralization mainly occurs within the crypto‐explosive breccia belt of subvolcanic intrusion. Constraints on the precise timing of mineralization are of fundamental importance for understanding the ore genesis of the Wulaga gold deposit and its mineralization potential. Three hydrothermal stages have been identified: the early veiny quartz–euhedral pyrite stage; the fine pyrite–marcasite–gray or black chalcedony stage; and the late carbonate–pyrite stage. The Rb–Sr dating of gold‐bearing pyrites from the fine pyrite–marcasite–gray or black chalcedony stage is 113.8 ± 4.4 Ma with an initial ⁸⁷Sr/⁸⁶Sr ratio of 0.706346 ± 0.000019. The age of the gold deposit is consistent with the age of ore‐bearing volcanic (109–113 Ma) and subvolcanic intrusion (103–112 Ma) within the error limits, and the pyrite initial ratio has an identical value of ⁸⁷Sr/⁸⁶Sr to subvolcanic intrusion (0.705547 ± 0.000012). These indicate that crystallization of the wall rock and epithermal gold mineralization was coeval and likely cogenetic. Moreover, a lot of epithermal gold deposits that formed in Early Cretaceous volcanic and subvolcanic intrusions have been discovered in recent years in Heilongjiang province. Combined with the studies of tectonic and magmatic activities, we propose that the formation of the Wulaga gold deposit might be caused by the heated circum‐flow water related to the volcanic–subvolcanic intrusive hydrothermal event triggered by the ancient subduction of the Izanagi plate in the Early Cretaceous.     

~(40)Ar-~(39)Ar Age of K-feldspar from K-feldspar Granite in the Qiaohuote Copper Deposit, Bayanbulak, Xinjiang, and Its Geological Significance

By using the 40Ar-39Ar chronological method to date K-feldspar from K-feldspar granite in the Qiaohuote copper district, the authors obtained a plateau age of 274.78±0.44 Ma and an isochron age of 272.7±3.0 Ma. Because there is no tectonic deformation overprinted or hydrothermal alteration in the K-feldspar granite intrusion after its emplacement, the 40Ar-39Ar age represents the crystallization age of K-feldspar in K-feldspar granite, i.e. the late crystallization age of the K-feldspar granite intrusion, which indicates that the K-feldspar granite formed in the intraplate extensional stage during the Early Permian. Moreover, based on the spatial relationship between the K-feldspar granite intrusion and copper orebodies, variations of copper ore grade, REE characteristics of K-feldspar granite and copper ores, and H and O isotopic compositions of fluid inclusions in copper ores, the metallogenesis of the Qiaohuote copper deposit is directly related to intrusive activities of the K-feldspar granite, and     

个旧卡房层状铜矿床金云母和云英岩化白云母40Ar-39Ar同位素年龄及意义

在个旧锡铜多金属矿集区发育有矽卡岩型和热液脉型等锡铜矿化体,其形成时代是晚白垩世,属与花岗岩有关的岩浆热液成因矿床。赋存于三叠纪蚀变玄武岩层中,呈(似)层状的铜矿体的精确年龄尚未有报道,成因仍备受争议。文章选择赋存于卡房矿田蚀变玄武岩层中,呈(似)层状分布的铜矿体中的金云母,及新山岩体接触带云英岩中的白云母为研究对象,利用⁴⁰Ar-³⁹Ar阶段加热同位素定年方法对它们进行了年代学研究,获得了金云母和白云母的⁴⁰Ar-³⁹Ar同位素坪年龄分别为(79.55±0.47) Ma和(79.53±0.57) Ma,对应等时线年龄分别为(79.8±1.3) Ma和(79.7±1.0) Ma,反等时线年龄分别为(79.7±2.0) Ma和(79.61±0.75) Ma,两者年龄基本一致。结合矿物共生组合特征和流体包裹体测温资料,认为金云母的坪年龄(79.55±0.47) Ma,可以代表卡房蚀变玄武岩中(似)层状铜矿的形成时代,而白云母的坪年龄(79.53±0.57) Ma,则代表新山岩体形成后期岩浆热液活动的年龄。这2个年龄与个旧锡铜多金属矿床的成矿时代基本一致,应是同一构造-岩浆-流体活动形成的成矿系列产物。     

40Ar/39Ar age of adularia from veins of the Tokur gold deposit, the Mongolian-Okhotsk Orogenic Belt, Russia

The ⁴⁰Ar/³⁹Ar age of the productive stage of the ore-forming hydrothermal process at the large Tokur gold deposit is 122.4 ± 2.0 Ma. This estimate suggests a paragenetic relationship of this deposit with the nearly exposed Karaurak subvolcanic trachyrhyodacite intrusion, the U—Pb zircon age of which was previously estimated at 120 ± 5 Ma. The age of mineralization at the Tokur deposit is close to the time of formation of some other deposits in the Russian Far East localized in various structural units.     

Metallogenic Epoch of Nonferrous Metallic and Silver Deposits in the Jiaodong Peninsula, China and its Geological Significance

As China's most important gold-producing district,the Jiaodong Peninsula also contains copper,lead-zinc,molybdenum(tungsten),and other nonferrous metal ore deposits,but the space-time and genetic relationships with gold deposits remain uncertain.To investigate the temporal relationship between these nonferrous metal and gold ore deposits,We collected the samples from a number of nonferrous metallic and silver deposits and metallogenetic rock bodies in the eastern Jiaodong Peninsula for isotopic dating.The results show that the Re-Os isotopic model ages of the Lengjia molybdenum deposit in Rongcheng range from 114.5± 1.8 Ma to 112.6± 1.5 Ma,with an average age of 113.6± 1.6Ma;the LA-ICP-MS ~(206)Pb/~(238)U ages of 33 zircons in the sericitization porphyritic monzogranite that hosts the Tongjiazhuang silver deposit in Rongcheng range between 122 Ma and 109 Ma,with a weighted mean age of 116.04± 0.95 Ma;the LA-ICP-MS ~(206)Pb/~(238)U ages of 31 zircons in the copper metallogenic pyroxene monzodiorite that hosts the Kuangbei copper deposit in Rongcheng range from126 Ma to 106 Ma,with a weighted mean age of 116.6± 1.7 Ma;and the LA-ICP-MS ~(206)Pb/~(238)U ages of19 zircons in the pyroxene monzodiorite surrounding the Dadengge gold and multimetal deposit in Weihai range from 113 Ma to 110 Ma,with a weighted mean age of 111.7± 0.6 Ma.All these results indicate that the metallogenic ages of the silver and nonferrous metallic deposits in the Jiaodong Peninsula are in a limited range from 118 Ma to 111 Ma.Previous studies have demonstrated that the isotopic ages of gold deposits in the Jiaodong Peninsula range from 123 Ma to 110 Ma,while Weideshanian magmatism occurred between 126 Ma to 108 Ma.Both these ranges are grossly consistent with the metallogenic ages of silver and nonferrous metallic deposits in this study,suggesting that the large-scale mineralization occurred in the Early Cretaceous when magmatic activities were strong.This epoch may be linked to the lithosphere thinning and the thermo-upwelling extension in eastern China at that time.In addition,field investigation also shows that gold and nonferrous metallic deposits are distributed nearby the Weideshanian granite,with the nonferrous metallic deposits lying within or surrounding the granite pluton and the gold deposits outside the granite pluton.We propose the following mineralization scenario:In the Early Cretaceous,an intensive lithospheric extension induced partial melting and degassing of the metasomatized lithospheric mantle,which resulted in the formation of mantle-derived fluids enriched in metal elements.During the rapid process of magma ascent and intrusion,crust-derived fluids were activated by the magmatic thermal dome and served to further extract ore-forming materials from the crust.These fluids may have mixed with the mantle-derived fluid to form a crust-mantle mixing-type ore-forming fluid.The high-temperature conditions in the center or in contact with the granitic magmatic thermal dome would have been favorable for the formation of porphyry-type,skarn-type,and hydrothermal-vein-type ores,thus forming a series of Mo(W),Cu,and Pb-Zn deposits in the mid-eastern Jiaodong Peninsula.In contrast,the medium-to low-temperature conditions in the periphery of the magmatic thermal dome would have favored the deposition of gold(silver) ores under the appropriate physiochemical and structural conditions.The metallogenic epoch of the molybdenum,copper,and silver deposits,and their spatio-temporal and genetic relations to the gold deposits,as demonstrated in this study,not only provide important insights to the study of regional metallogeny,our understanding of the metallogenesis of the Jiaodong type gold deposit,and the geodynamic background of the large-scale mineralization in the Jiaodong Peninsula,but also have practical value in guiding the mineral exploration.     

冀东峪耳崖金矿床蚀变绢云母40Ar-39Ar年龄 及其地质意义

峪耳崖大型金矿床位于华北克拉通北缘燕山造山带东段,其主成矿阶段的时间尚待准确约束。本次工作开展了主成矿阶段矿石中蚀变绢云母40Ar-39Ar同位素定年研究,获得的坪年龄((169.4±1.1)Ma(MSWD=0.22)),与反等时线年龄((168.4±1.8)Ma(MSWD=5.5))一致,小于赋矿花岗岩的年龄(174～175 Ma)和辉钼矿的ReOs等时线年龄(172 Ma),限定了峪耳崖金矿主成矿过程自172 Ma持续至169 Ma。峪耳崖金矿与冀东地区其他金矿床显示相似的成岩成矿特征,均在中侏罗世蒙古-鄂霍次克洋闭合、两侧板块碰撞造山的远程影响下,冀东地区下地壳基底物质部分熔融形成的花岗质岩浆(可能伴有少量幔源物质混入)及其分异出的岩浆热液萃取基底成矿物质后,成矿流体在NE向构造有利空间发生沉淀富集,形成岩浆期后热液型金矿床。     

福建省泰宁县何宝山金矿床长兴岩体锆石LA-ICP-MS U-Pb年龄及其地质意义

长兴钾长混合花岗岩体与何宝山金矿床的成矿作用关系密切。何宝山金矿床的成矿作用表现出多期次、多阶段的特点,加里东晚期长兴岩体的侵入活动促进了金矿床成矿物质早期的迁移和富集,印支晚期—燕山早期的构造-岩浆活动叠加成矿。文中对区内加里东期主要侵入岩体进行了锆石LA-ICP-MS U-Pb同位素定年研究,得出长兴岩体的成岩年龄为(437.1±1.3)Ma,黑云母石英闪长岩成岩年龄为(436.6±1.1)Ma,黑云母花岗闪长岩脉成岩年龄为(427.1±1.4)Ma,从而确定金矿床成矿期上限,为进一步成矿作用研究提供科学依据。     

黑龙江嘉荫连珠山金矿床成岩成矿年代学及其地质意义

连珠山矿床位于小兴安岭北麓,是一个产于花岗岩内部断裂体系的蚀变岩型金矿床。为了限定其成矿时代与成矿地质背景,本文对其赋矿围岩黑云母二长花岗岩和石英闪长岩进行了岩石地球化学、锆石U-Pb和绢云母40Ar/39Ar年代学的系统研究。定年结果表明黑云母二长花岗岩形成时代为中三叠世(243.7±1.3Ma,MSWD=0.77,n=12),岩浆上侵过程中受到早古生代(474~438Ma)和中二叠世(267~261Ma)的岩浆混染,而石英闪长岩形成于晚三叠世(215.3±1.3Ma,MSWD=0.35,n=17);黄铁绢英岩化矿石中的绢云母40Ar/39Ar坪年龄为194.2±2.0Ma,指示为早侏罗世成矿;元素地球化学特征显示连珠山侵入岩为准铝质-弱过铝质、高钾钙碱性岩石系列,具有I型花岗岩的地球化学属性;轻稀土元素富集,相对亏损重稀土元素,且具有弱的负Eu异常;富集大离子亲石元素(LILE),亏损高场强元素(HFSE)。结合小兴安岭-张广才岭地区已有年代学资料和区域构造演化特征,认为其成矿地质背景为兴蒙造山晚期与古太平洋板块俯冲转换期,或成矿发生在兴蒙造山期后的伸展阶段。     

Geochemistry,zircon U–Pb analysis,and fluid inclusion 40Ar/39Ar geochronology of the Yingchengzi gold deposit,southern Heilongjiang Province,NE China

The Yingchengzi gold deposit, located 10 km west of Shalan at the eastern margin of the Zhangguangcai Range, is the only high commercially valuable gold deposit in southern Heilongjiang Province, NE China. This study investigates the chronology and geodynamic mechanisms of igneous activity and metallogenesis within the Yingchengzi gold deposit. New zircon U–Pb data, fluid inclusion ⁴⁰Ar/³⁹Ar dating, whole‐rock geochemistry and Sr–Nd isotopic analysis is presented for the Yingchengzi deposit to constrain its petrogenesis and mineralization. Zircon U–Pb dating of the granite and diabase–porphyrite rocks of the igneous complex yields mean ages of 471.7 ± 5.5 and 434 ± 15 Ma respectively. All samples are high‐K calc‐alkaline or shoshonite rocks, are enriched in light rare earth elements and large ion lithophile elements, and are depleted in high field strength elements, consistent with the geochemical characteristics of arc‐type magmas. The Sr–Nd isotope characteristics indicate that the granite formed by partial melting of the lower crust, including interaction with slab‐derived fluids from an underplated basaltic magma. The primary magma of the diabase–porphyrite was likely derived from the metasomatized mantle wedge by subducted slab‐derived fluids. Both types of intrusive rocks were closely related to subduction of the ocean plate located between the Songnen–Zhangguangcai Range and Jiamusi massifs. However, fluid inclusion ⁴⁰Ar/³⁹Ar dating indicates that the Yingchengzi gold deposit formed at ~249 Ma, implying that the mineralization is unrelated to both the granite (~472 Ma) and diabase–porphyrite (~434 Ma) intrusions. Considering the tectonic evolution of the study area and adjacent regions, we propose that the Yingchengzi gold deposit was formed in a late Palaeozoic–Early Triassic continental collision regime following the closure of the Paleo‐Asian Ocean. In addition, the Yingchengzi deposit could be classified as a typical orogenic‐type gold deposit occuring in convergent plate margins in collisional orogens, and unlikely an intrusion‐related gold deposit as reported by previous studies. Copyright © 2015 John Wiley & Sons, Ltd.     

Geochronological Constraints Using 40Ar/39Ar Dating on the Mineralization of the Hishikari Epithermal Gold Deposit, Japan

Abstract. Ages for thirty adularia samples collected from various veins were in the Hishikari gold deposit determined by ⁴⁰Ar/³⁹Ar dating to constrain the timing of adularia‐quartz vein formation and to determine the temporal change in temperature of hydrothermal fluid. Plateau ages were obtained from all adularia samples, and significant excess ⁴⁰Ar is not recognized from inverse isochrones. The duration of mineralization within individual veins was determined by adularia ages from the early and late stages of mineralization within the same vein. The durations of mineralization in the Daisen‐1, Daisen‐3, Hosen‐2 and Keisen‐3 veins in the Honko‐Sanjin zone were 7,000, 140,000, 160,000 and 170,000 years, respectively. The durations of mineralization in the Seisen‐2 and Yusen‐1–2 veins in the Yamada zones were 360,000 and 320,000 years, respectively. Mineralization lasted for a relatively longer period in individual veins at the Yamada zone. Mineralization ages from the Honko‐Sanjin zone range from 1.04 to 0.75 Ma, and most mineralization ages are concentrated in a short period from 1.01 to 0.88 Ma. In contrast, mineralization ages for the Yamada zone range from 1.21 to 0.64 Ma. These results indicate that fracturing and subsequent vein formation lasted for a longer period in the Yamada zone (about 570,000 years) compared with those events in the Honko‐Sanjin zone (about 290,000 years). The homogenization temperatures of liquid‐rich fluid inclusions in columnar adularia used for age determination were determined to be 223°C on average, and most of these temperatures range from 180 to 258d?C. No significant temporal change in homogenization temperature is recognized in this study. However, adularia in the Keisen veins indicated higher homogenization temperatures compared with elsewhere in the deposit, suggesting that the principal ascent of mineralizing hydrothermal fluid was via the Keisen veins.     

江南过渡带东至查册桥金矿床~(40)Ar-~(39)Ar年代学及成矿条件研究

查册桥金矿是近年来在江南过渡带发现的一个金多金属矿床,本文对该矿床与矿化有关的蚀变花岗闪长斑岩中绢云母进行了~(40)Ar-~(39)Ar年龄测试,获得蚀变岩金矿石绢云母坪年龄156.9±1.6 Ma,等时线年龄152±28 Ma和矿化强蚀变花岗闪长斑岩绢云母坪年龄142.1±1.3 Ma,等时线年龄137±13 Ma。程檀矿段与牛头高家矿段流体包裹体均一温度为160℃左右,氢氧同位素特征显示成矿热液以岩浆热液为主。结合本区及邻近矿区相关研究成果,本区金矿主要为浅成、低温型,成矿物质和热液具有多来源特征,原生金矿以微细粒浸染型为主,具类卡林型金矿矿化特征,其年龄值分别对应于燕山期不同阶段构造活动和成岩成矿作用时代,其成矿过程经历了中侏罗世韧-脆性挤压构造变形和蚀变、矿化,晚侏罗世-早白垩世早期与岩体侵入相关的金多金属矿化,以及早白垩世中、晚期浅成低温热液成矿作用。     

The Thermal History of the Huangmeijian Granite Intrusion in Anhiii and Its Relation to Mineralization: Isotopic Evidence

Abstract Whole—rock Rb—Sr, zircon U—Pb and hornblende, biotite and K—feldspar K—Ar ages are used to reconstruct the cooling history of the Huangmeijian intrusion in the Anqing—Lujiang quartz—syenite belt in Anhui. Oxygen isotope geothermometry of mineral pairs demonstrates that diffusion is a dominant factor controlling the closure of isotopic systems. Assuming the cooling of the intrusion is synchronous with a dicrease in local geothermal gradients, an emplacement depth of about 8 km and the magma crystallization temperature of 800 ± 50°C are estimated. The Huangmeijian intrusion experienced a rapid cooling process and uplifted after its emplacement and crystallization at 133 Ma B.P. with a cooling rate of 34.5°C / Ma and an uplifting rate of 0.35 mm/ a. The intrusion was rising until it rested at a depth of 3 km at a temperature of 300 ± 50°C about 14 Ma later. Then the intrusion was in slow cooling and uplifting with a cooling rate of 4.4°C / Ma and an uplifting rate of 0.04 mm/ a. U—Pb dating of pitchblende is done for the hydrothermal uranium deposit formed in the contact zone of the Huangmeijian intrusion. The result shows that the mineralization age is close to the closing time of the K—Ar system in biotite. The fluid inclusion thermometry indicates that the mineralization temperature is in agreement with the closure temperature of the biotite K—Ar system. This suggests a close relationship between the slow cooling of the intrusion and the hydrothermal uranium mineralization process.     

吉林小西南岔金-铜矿床成矿流体地球化学特征及矿床成因研究

小西南岔金-铜矿床产于海西期花岗闪长岩-石英闪长岩体之中,其矿化类型以石英大脉及石英细脉带型金-铜矿化为主,局部地段叠加发育有石英脉型辉钼矿化。流体包裹体研究结果表明,矿区金-铜矿脉及辉钼矿脉石英中均主要发育含NaCl子矿物三相、气相-富气相及气液两相三种类型的原生流体包裹体,同类包裹体均一温度、盐度等参数相近,显示两类矿化成矿流体具有相似的地球化学性质,氢-氧同位素研究结果反映它们均主要来源于岩浆热液。辉钼矿Re-Os同位素定年研究表明区内辉钼矿化主要发生于109Ma±,而金-铜矿脉石英的40Ar-39Ar同位素定年结果表明金-铜矿化则主要发生于123.35±0.8Ma。结合矿区已有的岩浆岩年代学研究成果,提出小西南岔矿区金-铜矿化主要与燕山晚期细粒(花岗)闪长岩活动有关,而辉钼矿化则与其后侵位的隐伏花岗斑岩活动有关的认识。     

赣南银坑矿田高山角花岗闪长岩SHRIMP U-Pb定年及其与成矿的关系

高山角花岗闪长岩体位于南岭成矿带东段之北部,南岭东西向构造与滨太平洋北北东向构造带的交汇复合部位。岩体产出于银坑贵多金属矿田内部,与区内金银铅锌铜的成矿作用密切相关。在矿田地质和岩体地质工作基础上,采用SHRIMP锆石U-Pb法对高山角花岗闪长岩进行了精确定年,获得岩体锆石年龄为(160±1)Ma,并存在(422±4)Ma的捕获岩浆锆石年龄,指示岩体形成于燕山早期,而并不是以往认为的早白垩纪。结合矿床地质资料,判断矿田内的贵多金属成矿作用与高山角岩浆活动同期,与赣南地区中生代(165～150 Ma)大规模钨锡成矿作用产于同一时期、同一构造背景,同属一个成矿系列。     

The Pogromnoe deposit as an unconventional commercial type of gold mineralization in Transbaikalia

We studied the mineralogic and geochemical features of metasomatic rocks and ores from the Pogromnoe gold deposit, which is unconventional for Transbaikalia. The deposit, which formed in the Early Cretaceous, at the rifting stage of the regional evolution, is localized in the dynamoclastic strata of the Mongol-Okhotsk suture, along which the Siberian continent joined the Mongolia-China continent in the Early-Middle Jurassic. Gold mineralization occurs as two morphologic types of ores: stockwork quartz-carbonate-arsenopyrite-pyrite ores in altered volcanics (orebody no. 1) and veinlet-vein quartz ones (with disseminated sulfides) in altered carbonaceous shales (orebody no. 10). The host rocks of the deposit are the highly altered volcanosedimentary rocks of the Butorovskii Formation (Shadoron Group, J_2–3), which transformed into metasomatic (by composition) and dynamoclastic (by texture and structure) rocks. It has been found that the formation of the metasomatic rocks and mineralization proceeded in several stages. Propylites formed at the preore stage (J₃); tectonic schists and albitophyres, at the late preore stage; and sericitolites and albite-carbonate-sericite-quartz metasomatic rocks (quartzites), at the synore stage. The ⁴⁰Ar/³⁹Ar age of the stockwork system of ore-bearing fractures and metasomatic rocks which formed at the late preore stage is estimated as 139.5 ± 1.8 Ma. The gold-bearing rocks at the deposit are the late preore and synore metasomatic rocks formed after volcanics with sulfide mineralization (gold concentrators are pyrite II and III and arsenopyrite I and II) and after altered carbonaceous shales (gold concentrators are vein quartz and arsenopyrite II). Gold grade is completely consistent with silicification, saturation with quartz-sulfide and sulfide microveinlets, and fine sulfide dissemination. By genesis, the Pogromnoe deposit belongs to objects which formed in shear zones with the contribution of gold-bearing mantle fluids. The authors presume that the sources of mineralization are the ore-producing granitoids of the Amudzhikan-Sretensk intrusive assemblage within the Aprelkovo ore-magmatic system (OMS) (Os’kina and Urguchan plutons). This is confirmed by Pb isotope compositions (²⁰⁷Pb/²⁰⁴Pb and ²⁰⁶Pb/²⁰⁴Pb) for the pyrite and arsenopyrite of the Pogromnoe gold-bearing ores, which testify to the widespread occurrence of “mantle” Pb isotope signatures. The ⁴⁰Ar/³⁹Ar age of the ore-producing granitoids of the Aprelkovo OMS is 131.0 ± 1.2 Ma. Gold in the orebodies occurs in native form and is fine and very fine. By gold grade, the Pogromnoe deposit deserves very close attention as a new commercial type of gold mineralization in Transbaikalia.     

陕西凤太矿集区柴蚂金矿床成矿时代的40Ar/39Ar年龄证据

柴蚂金矿床位于陕西凤太矿集区的西北部,矿体产于长沟-八卦庙向斜和长沟-打柴沟背斜核部和两翼的NWW向脆韧性剪切构造带中,赋矿地层为上泥盆统星红铺组的斑点状铁白云质粉砂质千枚岩。金矿化类型包括石英脉型和蚀变岩型2种。成矿过程划分为早期石英-碳酸盐阶段、主成矿期石英-碳酸盐-硫化物阶段和晚期石英脉阶段。对主成矿阶段热液蚀变形成的绢云母开展40Ar/39Ar测年研究,获得坪年龄为(219.0±2.0)Ma,指示其成矿作用始于219 Ma左右,即晚三叠世。前期工作获得该阶段碳酸盐矿物的Sm-Nd同位素年龄为(203.0±1.6)Ma,2个年龄值可能限定了成矿作用的上限与下限。结合前人有关区域地质与成矿作用的研究成果分析认为,柴蚂金矿床属于造山型金矿床,其成矿作用的多阶段性与剪切带长期演化过程中的构造递进变形密不可分。