Suckling Dome and the Australian–Woodlark plate boundary in eastern Papua: the geology of the Keveri and Ada'u Valleys

The Owen Stanley Fault Zone (OSFZ) is the low-angle thrust boundary between the Australian and Woodlark plates. The eastern extension of the OSFZ links with the Woodlark Basin spreading centre. Recent tectonic models of eastern Papua depict the OSFZ boundary passing through the Mt Suckling district, with the Keveri Fault a key component. Gravity data clearly show that the OSFZ and the Papuan Ultramafic Belt (PUB) pass north of Mt Suckling. Tectonised mafic and ultramafic rocks of the Mt Suckling district, previously referred to the PUB, are reassigned to the Awariobo Range Complex (new name). Extensive pillow basalts previously referred to the middle Eocene part of the Kutu Volcanics at the top of the PUB sequence are, in the map area, reassigned on lithological and biostratigraphic grounds to the late Oligocene–middle Miocene Wavera Volcanics. The detailed work reported here indicates that the Keveri Fault is unrelated to the OSFZ with no evidence for thrusting along the structure. The area's tectonic history has been dominated by large vertical displacements along the Keveri Fault. The commencement of late Miocene buoyant uplift of the Suckling Dome (new name), related to granite intrusion into thick crust of the eastern Papua region, marks the inception of the Keveri Fault and coincides with the initiation of Woodlark rifting. The fault facilitated much of the rapid vertical movement of the dome, with an estimated 8000 m of uplift (2.5 m/10³ a) since the late Miocene. Movement on the Keveri Fault is notably different from structures flanking other metamorphic core complexes in eastern Papua. There is no field evidence for the development of a low-angle, south-dipping detachment fault along the southern margin of the Suckling Dome. The Suckling Dome is the westernmost of the eastern Papua domes, localised within a broad extensional zone that continues to propagate westward along the OSFZ plate boundary.     

新西兰科罗曼德尔半岛金（铜）矿床地质特征、成因及找矿意义

新西兰科罗曼德尔半岛火山岩带是世界知名的浅成低温热液型金矿成矿省,也是新西兰最为重要的金银矿矿集区,在环太平洋成矿带内占有重要的地位。科罗曼德尔半岛浅成低温热液型金矿主要赋存于科罗曼德尔群中新世安山岩和英安岩中,矿化类型主要为石英脉型和角砾岩型2种。矿床的成矿流体特征表现出明显的大气降水特征,并显示有少量的岩浆水加入,成矿物质具岩浆来源特征,为石英±方解石±冰长石±伊利石亚型浅成低温热液型金矿。区内金矿成矿时代为16．3-2．0Ma,主要集中于7．0-6．0Ma之间,金矿的大规模形成与诺特兰德火山弧与科尔维一劳火山弧共同作用有关,区域构造背景由挤压转变为伸展环境的转折期,为金矿形成的高峰期。区内零星出露与浅成低温热液型金矿化有关的斑岩型铜矿化表明,该地区具有较好的斑岩型铜矿化潜力。     

豫西熊耳山矿集区栾灵金矿床辉钼矿Re-Os同位素年龄及其地质意义

豫西栾灵金矿床地处熊耳山金多金属矿集区南部马超营断裂带北侧,金矿体产于构造破碎带中,呈钾长石石英脉体和蚀变岩产出,为本区一种新的金矿化类型。文章为厘定栾灵金矿床的成矿时代,采用辉钼矿Re-Os同位素定年方法,测得栾灵金矿6件辉钼矿样品的Re-Os同位素模式年龄为(161±3)Ma~(164±2)Ma,加权平均年龄(163±1)Ma(MSWD=0.68),等时线年龄(163±2)Ma(MSWD=1.5),表明栾灵金矿床形成于晚侏罗世早期。与祁雨沟、前河金矿等早白垩世(125 Ma)金矿相比,栾灵金矿的成矿作用早约38 Ma。这些年龄数据表明,该矿床在区域上可能与南泥湖-三道庄、上房沟钼矿等形成于同一成矿系统,它的发现为在熊耳山地区寻找相似成矿地质条件的金、钼矿床提供了依据。     

内蒙古大青山地区金矿床类型、控矿规律及找矿方向

内蒙古呼和浩特地区主要有三种类型金矿床：构造蚀变岩型、中基性岩浆热液型和绿岩型。它们分别受控于不同地质条件：构造蚀变岩型主要受控于韧性剪切带或断裂带构造，中基性岩浆热液型主要受控于中基性幔源的埃达克岩-赞岐状岩-富Nb辉长岩，绿岩型金矿主要受二道洼群地层控制。然而，这些矿床成因复杂，往往受控于多个成矿因素，当上述两个以上成矿条件同时存在时，成矿的可能性就会增大。如绿岩型金矿主要受控于二道洼地层，但矿体主要受韧性剪切带或断裂构造的叠加部位控制。因此，在本区寻找以上三种类型的金矿床，特别注意在二道洼群地层、中基性幔源埃达克岩-赞岐状岩-富Nb辉长岩附近和韧性剪切带或断裂构造叠加部位。另外，由于与中基性岩有关的矿床还未引起足够重视，注意寻找该类型矿床就显得很有必要。     

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.     

Quantification constraints on time gap for comagmatic gold deposits： Evidence from chronological statistics

The time gap between diagenesis and mineralization （TGDM） for comagmatic gold deposits （CGD） plays an important role in confirming the genetic relationship between gold deposits and their related intrusions. With the help of preciously published isotopic ages of some typical gold deposits and their related rocks in China, the authors have discussed and quantified the distribution characteristics and scope of the TGDM. Statistical analyses and Kolmogorov tests showed that mineralizing events are either contemporaneous with or slightly postdate their cognate magma. The TGDM conforms with normal distributions at a 0.05 confidence level and clusters between 0 and 16.0 Ma with a mean of 7.0 Ma. Thus, if the TGDM of CGD is less than 16.0 Ma, it is reasonable to consider, with the aid of other evidence, the possibility of its comagmatic genetic affiliation. The authors also emphasized that to get a precise time gap it is necessary to strengthen the diagenesis-mineralization geological background of the deposits studied, and to pay attention to the study of time gap in combination with trace elements and isotope tracing.     

Petrology and Geochemistry of the Bandas del Sur Formation, Las Canadas Edifice, Tenerife (Canary Islands)

The Bandas del Sur Formation preserves a Quaternary extra-calderarecord of central phonolitic explosive volcanism of the LasCañadas volcano at Tenerife. Volcanic rocks are bimodalin composition, being predominantly phonolitic pyroclastic deposits,several eruptions of which resulted in summit caldera collapse,alkali basaltic lavas erupted from many fissures around theflanks. For the pyroclastic deposits, there is a broad rangeof pumice glass compositions from phonotephrite to phonolite.The phonolite pyroclastic deposits are also characterized bya diverse, 7–8-phase phenocryst assemblage (alkali feldspar+ biotite + sodian diopside + titanomagnetite + ilmenite + nosean–haüyne+ titanite + apatite) with alkali feldspar dominant, in contrastto interbedded phonolite lavas that typically have lower phenocrystcontents and lack hydrous phases. Petrological and geochemicaldata are consistent with fractional crystallization (involvingthe observed phenocryst assemblages) as the dominant processin the development of phonolite magmas. New stratigraphicallyconstrained data indicate that petrological and geochemicaldifferences exist between pyroclastic deposits of the last twoexplosive cycles of phonolitic volcanism. Cycle 2 (0·85–0·57Ma) pyroclastic fall deposits commonly show a cryptic compositionalzonation indicating that several eruptions tapped chemically,and probably thermally stratified magma systems. Evidence formagma mixing is most widespread in the pyroclastic depositsof Cycle 3 (0·37–0·17 Ma), which includesthe presence of reversely and normally zoned phenocrysts, quenchedmafic glass blebs in pumice, banded pumice, and bimodal to polymodalphenocryst compositional populations. Syn-eruptive mixing eventsinvolved mostly phonolite and tephriphonolite magmas, whereasa pre-eruptive mixing event involving basaltic magma is recordedin several banded pumice-bearing ignimbrites of Cycle 3. Theperiodic addition and mixing of basaltic magma ultimately mayhave triggered several eruptions. Recharge and underplatingby basaltic magma is interpreted to have elevated sulphur contents(occurring as an exsolved gas phase) in the capping phonoliticmagma reservoir. This promoted nosean–haüyne crystallizationover nepheline, elevated SO₃ contents in apatite, and possiblyresulted in large, climatologically important SO₂ emissions. KEY WORDS: Tenerife; phonolite; crystal fractionation; magma mixing; sulphur-rich explosive eruptions     

Development of a Continental Volcanic Field: Petrogenesis of Pre-caldera Intermediate and Silicic Rocks and Origin of the Bandelier Magmas, Jemez Mountains (New Mexico, USA)

The Miocene–Quaternary Jemez Mountains volcanic field(JMVF) is the site of the Valles caldera and associated BandelierTuff. Caldera formation was preceded by > 10 Myr of volcanismdominated by intermediate composition rocks (57–70% SiO₂)that contain components derived from the lithospheric mantleand Precambrian crust. Simple mixing between crust-dominatedsilicic melts and mantle-dominated mafic magmas, fractionalcrystallization, and assimilation accompanied by fractionalcrystallization are the principal mechanisms involved in theproduction of these intermediate lavas. A variety of isotopicallydistinct crustal sources were involved in magmatism between13 and 6 Ma, but only one type (or two very similar types) ofcrust between 6 and 2 Ma. This long history constitutes a recordof accommodation of mantle-derived magma in the crust by meltingof country rock. The post-2 Ma Bandelier Tuff and associatedrhyolites were, in contrast, generated by melting of hybridizedcrust in the form of buried, warm intrusive rocks associatedwith pre-6 Ma activity. Major shifts in the location, styleand geochemical character of magmatism in the JMVF occur withina few million years after volcanic maxima and may correspondto pooling of magma at a new location in the crust followingsolidification of earlier magma chambers that acted as trapsfor basaltic replenishment. KEY WORDS: crustal anatexis; fractional crystallization; Jemez Mountain Volcanic Field; Valles Caldera; radiogenic isotopes; trace elements     

胶东唐家沟金矿床独居石LA-ICP-MS U-Pb同位素年代学及其地质意义

唐家沟金矿床是胶东地区牟平-乳山金矿带内一典型石英脉型金矿床。矿体产出于昆嵛山岩体与古元古代荆山群变质岩接触带附近的昆嵛山岩体中,受唐家沟断裂及其次级北东向断裂控制。矿体呈串珠状等间距分布,沿走向分支复合、膨胀夹缩现象明显。围岩昆嵛山二长花岗岩锆石LA-ICP-MS U-Pb测年结果为157.57±0.82Ma,含金石英脉中热液独居石LA-ICP-MS U-Pb测年结果为122.1±2.8Ma,代表了金矿的成矿时代。结合近年来已有成果,认为昆嵛山岩体是陆陆挤压碰撞环境下,地壳部分熔融形成的,与金成矿无直接关系,为成矿前构造-岩浆活动的产物;早白垩世,古太平洋板块向欧亚板块俯冲,构造体制由挤压向伸展转换,形成一套壳幔混合型花岗岩,成矿作用发生于岩浆作用晚期,时代集中于117～122Ma,为牟平-乳山成矿带成矿期构造-岩浆活动的代表;110～120Ma,胶东地区岩石圈强烈减薄,在伸展的构造环境下发育的三佛山岩体,与成矿无直接关系。     

从纳哥金矿地质地球化学特征探讨黔西南卡林型金矿成因

在黔西南相同地质背景下出现的纳哥金矿特殊地质和地球化学特征:矿区出露大量的与成矿有关的巨大石英脉体,脉体中CO₂含量很高,成矿温度与区域矿床类似,H、O同位素组成在岩浆水附近,认为该矿床是深部岩浆源成因。通过区域卡林型金矿床物源、成矿作用、控矿构造等方面的总结、分析和对比讨论,认为黔西南金矿床应有统一的成因,为深部岩浆源(少量地层中物质混杂)-深大断裂导矿-表层断裂、背斜控矿-交代充填成矿的中偏低温热液矿床。     

西藏弄如日金矿床蚀变绢云母~(40)Ar-~(39)Ar年龄及其地质意义

西藏弄如日金矿是冈底斯成矿带发现的第一个浅成低温热液型金矿床。为确定金矿床的成矿时代,对该矿床与金矿化有关的蚀变花岗斑岩中绢云母进行了40Ar-39Ar年龄测试,获得绢云母的加权平均年龄和等时线年龄分别为19.87±0.96Ma和19.70±0.30Ma。结果表明,弄如日金矿床金矿化的主要成矿时代为中新世。该成果的获得对于进一步认识弄如日金矿成因机制、地球动力学背景以及区域找金突破具有重要意义。     

冀西北水泉沟杂岩体及与其有关金矿床的~(40)Ar-~(39)Ar同位素年代学研究

冀西北金矿集中区是我国华北地台北缘金矿成矿带的重要组成部分,区内金矿主要产于水泉沟碱性杂岩体及邻近的太古宙变质岩内。Ar-Ar同位素年龄测定结果显示,金矿床成矿年龄(172～188 Ma)与水泉沟碱性杂岩体的形成年龄(304～306 Ma)相差达120 Ma。综合研究推断金矿床不是碱性岩浆直接演化产物,而是在燕山期构造—岩浆活动影响下,地下循环热流体对矿源岩——碱性杂岩体淋滤、萃取,形成富含金的成矿热液,最终在有利的成矿构造部位沉淀富集的结果。因此本区的金矿床均属于与碱性杂岩体有关的改造型热液金矿。     

毛堂、蒲塘金矿稳定同位素地球化学及成因探讨

对毛堂、蒲塘金矿S、C、H、O、Si同位素地球化学特征及矿床产出地质环境研究表明,硫主要来自深部岩浆,成矿物质来自同熔岩浆,部分来自变质,基性火山岩基底,热液中水主要为大气降水.大气降水环流萃取花岗斑岩、角砾岩和围岩中的金,在斑岩顶部和隐爆角砾岩中成矿.     

美国福特-诺克斯金矿床产出环境、地质特征和形成作用

美国阿拉斯加州中东部福特—诺克斯(Fort Knox)金矿床是北极圈周缘规模最大的超大型金矿床之一。对该矿床的形成背景、矿体特征、形成模式的研究表明,该矿床主要产于前寒武纪—早古生代绿片岩与白垩纪—古近纪花岗质侵入岩接触带上,受构造-岩浆活动控制明显,地表出露面积为1100×600m2,并向深部逐渐变小。与其他与侵入岩有关的金矿床不同的是,该矿床热液蚀变作用强烈,与金矿化具密切空间分布关系的热液蚀变主要为钾长石化、钠长石化、绢云母化和青磐岩化。同位素年代学证据表明,其成矿时代为晚白垩世—古近纪(92.5±0.2Ma),是多期次岩浆作用的产物。依据同位素特征、成矿流体、围岩蚀变等特征可以判定,成矿物质主要来源于花岗质熔浆,成矿作用与氧化型中酸性侵入体侵入作用及其相关流体活动有关,属于典型的与侵入岩有关的金矿床。     

胶东和小秦岭:两类不同构造环境中的造山型金矿省

胶东和小秦岭是我国排名前两位的金矿产地,根据对这两个地区的实地野外考察、室内研究及对已有大量研究成果的总结,我们认为胶东与小秦岭地区的金矿床均可归入造山型金矿的范畴,它们分别形成于增生型造山体制和碰撞型造山体制.胶东金矿床形成于早白垩世(130～120Ma左右)与洋壳俯冲(增生)造山相关的活动大陆边缘环境,矿床主要产于中生代花岗岩岩体中,严格受断裂带(NNE向或NE向为主)控制,成矿流体具有低盐度高CO_2含量的特征,He-Ar同位素研究显示成矿过程有幔源物质的加入.综合金矿床及中生代岩浆岩(特别是与成矿近同时的早白垩世郭家岭花岗岩及基性岩脉)的地质地球化学特征与成岩成矿动力学,我们提出在俯冲的太平洋板块后退的背景下,胶东地区增厚地壳中的榴辉岩相下地壳及下伏岩石圈地幔发生两阶段拆沉,强烈的壳幔相互作用最终导致了早白垩世普遍的岩浆活动及金的爆发成矿的模式.小秦岭地区金矿床主要以大型含金石英脉的形式产出于太华群变质基底的脆性-韧性剪切带(EW向为主)中,而与区域内燕山期大型花岗岩岩基没有直接联系,矿床地质特征(如低盐度高CO_2,以变质流体为主的成矿热液)与造山型金矿吻合,He-Ar同位素特征表明金矿床形成时有幔源物质的加入.小秦岭地区脉状Au-Mo矿床印支期成矿年龄(215～256Ma,辉钼矿Re-Os)表明印支期是小秦岭地区金成矿的主要时期,小秦岭金矿属于陆陆(华北与扬子)碰撞造山过程中形成的造山型金矿.     

陕西周至马鞍桥金矿床地质特征及成因分析

阐述了马鞍桥金矿区的地层、构造、岩浆岩特征，总结了金矿床矿体、矿石及化学成分的基本特点，分析了围岩、剪切构造带、中酸性岩体与金矿化的关系，认为马鞍桥金矿的成矿物质来源于围岩泥盆系罗汉寺岩群，成矿作用严格受脆性剪切变形变质带控制，剪切同期中酸性岩浆活动为含矿热液上升迁移和富集成主矿体提供了必要的热能。含矿热液与韧性剪切变质岩之间交代作用的强度是导致金的沉淀和富集形成金矿体的关键。矿床为韧性剪切带蚀变岩型金矿。     

长白山火山活动历史、岩浆演化与喷发机制探讨

广义的长白山火山在我国境内包括著名的天池火山、望天鹅火山、图们江火山和龙岗火山,是我国最大的第四纪火山岩分布区。图们江火山和望天鹅火山活动都始于上新世,喷发活动分别介于上新世—中更新世（5.5~0.19 Ma）和上新世—早更新世（4.77 ~2.12 Ma）。天池火山和龙岗火山属于第四纪火山,喷发活动从早更新世（~2 Ma）持续到全新世。图们江火山岩为溢流式喷发的拉斑玄武岩,望天鹅火山、天池火山和龙岗火山母岩浆都是钾质粗面玄武岩,但经历了不同的演化过程。天池火山和望天鹅火山都经历了钾质粗面玄武岩造盾、粗面岩造锥和晚期碱性酸性岩浆（碱流岩和碱性流纹岩）的喷发;龙岗火山来自地幔的钾质粗面玄武岩浆则未经演化和混染直接喷出地表。图们江火山岩以溢流式喷发的拉斑玄武岩为主,少量玄武质粗安岩等。天池火山造盾之后,地壳岩浆房和地幔岩浆房具互动式喷发特点,来自地幔的钾质粗面玄武岩浆一方面在天池火山锥体内外形成诸多小火山渣锥,另一方面持续补给地壳岩浆房发生岩浆分离结晶作用和混合作用,分别导致双峰式火山岩分布特征和触发千年大喷发。火山岩微量元素和Sr-Nd-Pb同位素示踪揭示,长白山东（图们江火山、望天鹅火山和天池火山）、西（龙岗火山）两区显示地幔非均一性,东区岩浆源区具有软流圈地幔与富集岩石圈地幔混合特征,西区岩浆源区具有相对亏损的较原始地幔特征。西太平洋板块俯冲—东北亚大陆弧后引张是长白山火山活动的动力学机制。     

The Petrology of the Rotoiti Eruption Sequence, Taupo Volcanic Zone: an Example of Fractionation and Mixing in a Rhyolitic System

The Rotoiti eruption from the Taupo Volcanic Zone (TVZ) in northernNew Zealand produced voluminous pyroclastic deposits. The ferromagnesianmineral assemblage in these dominantly consists of cummingtonite+ hornblende + orthopyroxene with uniform magnesium/iron ratios;a second assemblage of biotite + hornblende + orthopyroxene,also with uniform Fe/Mg ratios, appears midway through the eruptionsequence and, thereafter, increases in abundance. These contrastingmineral assemblages, together with pumice clast and groundmassglass compositions, provide evidence for mingling of two discretemagmas. Similarities in the chemical characteristics of thetwo magmas suggest that they developed from a similar source.The eruption initially tapped relatively homogeneous magma thatwas erupted throughout most of this phase of activity. The middlestages of the eruption included some mixed magma. The finalstages of the eruption were dominated by a second magma composition,which was probably injected into the bottom of the main magmabody as the eruption proceeded. The source that fed the eruptionwas complex, and discrete magma bodies existed and evolved separatelyprior to the eruption. We conclude that eruptions in the TVZare fed from a diffuse upper-crustal zone of partially interconnected,and at times physically separate, magma bodies rather than fromcentralized and necessarily large long-lived magma chambers. KEY WORDS: Taupo Volcanic Zone; Okataina Volcanic Centre; Rotoiti eruption; rhyolite system; magma mixing     

Geology,geochronology, geochemistry and ore genesis of the Wangu gold deposit in northeastern Hunan Province,Jiangnan Orogen,South China

The Wangu gold deposit in northeastern Hunan, South China, is one of many structurally controlled gold deposits in the Jiangnan Orogen. The host rocks (slates of the Lengjiaxi Group) are of Neoproterozoic age, but the area is characterized by a number of Late Jurassic–Cretaceous granites and NE-trending faults. The timing of mineralization, tectonic setting and ore genesis of this deposit and many similar deposits in the Jiangnan Orogen are not well understood. The orebodies in the Wangu deposit include quartz veins and altered slates and breccias, and are controlled by WNW-trending faults. The principal ore minerals are arsenopyrite and pyrite, and the major gangue minerals are quartz and calcite. Alteration is developed around the auriferous veins, including silicification, pyritic, arsenopyritic and carbonate alterations. Field work and thin section observations indicate that the hydrothermal processes related to the Wangu gold mineralization can be divided into five stages: 1) quartz, 2) scheelite–quartz, 3) arsenopyrite–pyrite–quartz, 4) poly-sulfides–quartz, and, 5) quartz–calcite. The Lianyunshan S-type granite, which is in an emplacement contact with the NE-trending Changsha-Pingjiang fracture zone, has a zircon LA-ICPMS U–Pb age of 142 ± 2 Ma. The Dayan gold occurrence in the Changsha-Pingjiang fracture zone, which shares similar mineral assemblages with the Wangu deposit, is crosscut by a silicified rock that contains muscovite with a ca. 130 Ma ⁴⁰Ar–³⁹Ar age. The gold mineralization age of the Wangu deposit is thus confined between 142 Ma and 130 Ma. This age of mineralization suggests that the deposit was formed simultaneously with or subsequently to the development of NE-trending extensional faults, the emplacement of Late Jurassic–Cretaceous granites and the formation of Cretaceous basins filled with red-bed clastic rocks in northeastern Hunan, which forms part of the Basin and Range-like province in South China. EMPA analysis shows that the average As content in arsenopyrite is 28.7 atom %, and the mineralization temperature of the arsenopyrite–pyrite–quartz stage is estimated to be 245 ± 20 °C from arsenopyrite thermometry. The high but variable Au/As molar ratios (>0.02) of pyrite suggest that there are nanoparticles of native Au in the sulfides. An integration of S–Pb–H–O–He–Ar isotope systematics suggests that the ore fluids are mainly metamorphic fluids originated from host rocks, possibly driven by hydraulic potential gradient created by reactivation of the WNW-trending faults initially formed in Paleozoic, with possible involvement of magmatic and mantle components channeled through regional fault networks. The Wangu gold deposit shares many geological and geochemical similarities as well as differences with typical orogenic, epithermal and Carlin-type gold deposits, and may be better classified as an “intracontinental reactivation” type as proposed for many other gold deposits in the Jiangnan Orogen.     

河南嵩县庙岭金矿地质特征与钾长石~（40）Ar/^（39）Ar定年

河南嵩县庙岭金矿位于华北陆块南缘熊耳山—外方山地区。矿床赋存于中元古界熊耳群火山岩中近南北向断裂带内,矿体呈似层状、透镜状产出,矿石具浸染状、细网脉状构造和微细粒它形粒状晶粒结构、交代结构,围岩热液蚀变有硅化、钾长石化、绢云母化、黄铁矿化等,矿化具有多阶段的特点,属破碎带蚀变岩型金矿。成矿热液蚀变矿物钾长石Ar-Ar法测年的结果：坪年龄为121.6Ma±1.2Ma,等时线年龄为117.0Ma±1.6Ma,表明矿床形成于早白垩世,与熊耳山地区祁雨沟、瑶沟等金矿床形成于同一时期,属与早白垩世构造-岩浆-流体活动有关的产物。