青海同仁县江里沟斑岩-矽卡岩型铜钨钼矿床辉钼矿Re-Os同位素年龄及其成矿意义

西秦岭同德—泽库多金属成矿带是青海省重要的矿产集中区之一,位于西秦岭北缘斑岩-矽卡岩型铜、钼、金成矿带的最西端。江里沟矿床是该区的重要组成部分,为一个典型的斑岩型-矽卡岩型铜钨钼矿床。本文利用Re-Os同位素定年方法对江里沟铜钨钼矿床进行了成矿时代测定,获得了5件样品辉钼矿的Re-Os同位素模式年龄范围为219.5±3.1~222.2±4.0Ma,等时线年龄为224.3±7.3Ma。矿区二长花岗岩SHRIMP锆石UPb年龄测定结果表明岩石存在两个期次结晶年龄232±4Ma和214±4Ma,矿区花岗岩可能是两个期次岩浆活动的产物。根据斑岩型矿床矿化晚于成矿母岩的特征,认为江里沟矿床成矿时代属晚三叠世,与矿区232Ma期次的岩浆侵入活动关系密切,成矿晚于成岩约8Ma,成矿与成岩时代基本一致,是西秦岭印支期构造-岩浆活动的产物。本次研究可以大致确定岗察复式岩体周边矿床成矿时限为243.8~214Ma,与区域西秦岭—东昆仑三叠纪构造岩浆作用和成矿时代一致,构成西秦岭北缘斑岩-矽卡岩型铜-钼-金成矿系统的一部分。     

青海加吾金矿床花岗斑岩脉锆石U-Pb年龄、Hf同位素特征及其地质意义

加吾金矿床大地构造上位于中央造山系"共和缺口"西缘,位于中央造山带多个块体交接转换的重要部位,其形成与区内印支期中酸性岩浆活动密切相关。对区内与金成矿关系密切的花岗斑岩脉中的锆石进行LA-ICP-MS U-Pb定年以及Lu-Hf同位素测试。测试结果显示,锆石206Pb/238 U加权平均年龄为233.4Ma±4.3Ma(MSWD=2.7),形成时代为中三叠世,与青海西秦岭地区其他印支中晚期中酸性岩浆岩形成时代相近;锆石εHf(t)值介于-12.35~-1.12之间,二阶段Hf模式年龄(tDM2)介于1.3Ga~2.0Ga之间,加吾金矿区内花岗斑岩的源区主要为早-中元古代地壳。相对较高的εHf(t)值的出现说明形成花岗斑岩脉的岩浆有一定幔源组分的加入。与加吾金矿成矿关系密切的花岗斑岩脉形成于陆-陆碰撞过程中挤压向伸展转换的地球动力学环境。由于俯冲陆壳板片断离,幔源岩浆上涌/底侵至下地壳底部,诱发增厚古老下地壳部分熔融产生壳-幔混合岩浆,在印支中期侵入到中下三叠统隆务河组地层中,为金矿的形成提供了热源和深部成矿流体。加吾金矿床成矿时代与花岗斑岩脉的成岩时间一致,即233.4 Ma±4.3 Ma。     

福建紫金山地区岩浆演化序列初探:锆石SIMS U-Pb年龄及Hf、O同位素证据

通过对福建紫金山地区不同岩石样品中岩浆锆石的SIMS U-Pb年龄和Hf、O同位素研究,对该地区岩浆序列以及源区组成、壳幔相互作用等进行初步探讨。结果显示,岩石样品中岩浆锆石的年龄(151~1514 Ma)较为分散,包含了从中元古代、震旦纪、早古生代晚期、晚三叠世到晚侏罗世的5个不同岩浆侵入时期。锆石的二阶段Hf亏损地幔模式年龄(t_(DM2)值)主要分布在古元古代,ε_(Hf)(t)数据也显示主要沿基性地壳演化线分布,指示古元古代时期的新生基性地壳可能是研究区中元古代直至晚侏罗世侵入岩形成的主要源区。锆石δ~(18)O及ε_(Hf)(t)值显示中元古代及震旦纪岩浆作用是幔源岩浆与古元古代基性地壳共同作用的结果;早古生代晚期和晚三叠世岩浆作用以壳源为主;至晚侏罗世,亏损地幔物质对岩浆作用的影响增加。     

东昆仑大岔沟地区晚三叠世侵入岩年代学、岩石地球化学特征及Hf同位素研究

东昆仑祁漫塔格大岔沟地区晚三叠世侵入岩岩性主要为中细粒二长花岗岩和花岗闪长岩,锆石LA-MC-ICP-MS U-Pb定年表明,二长花岗岩的形成年龄为(233±2)Ma,属晚三叠世岩浆活动产物。岩石地球化学特征上,里特曼指数σ为0.85~2.59,为钙碱性-高钾钙碱性系列;相对富集大离子亲石元素Rb和K,亏损Ba、Ta、Nb、Sr、P和Ti等元素;轻稀土元素明显富集,轻重稀土元素分馏较强,具有较强的Eu负异常;花岗岩含角闪石且SiO_2与P_2O_5具明显负相关性,指示其属I型花岗岩。二长花岗岩锆石ε_(Hf)(t)值为–10.36~+1.6,二阶段Hf模式年龄变化范围为1164~1922 Ma,可能主要由中元古代地壳物质部分熔融形成,并有少量古元古代地壳物质和幔源物质加入,岩浆在演化过程中存在分离结晶作用。综合分析认为大岔沟地区晚三叠世可能处于碰撞-后碰撞转换阶段,加厚地壳的拆沉作用导致幔源岩浆底侵下地壳,使其部分熔融形成区内侵入岩。     

赣南地区寒武纪高滩组碎屑锆石U-Pb年龄和Hf同位素特征及地质意义

寒武纪高滩组广泛分布于赣南武功山-雩山地区,主体为一套浅变质砂岩夹板岩的复理石建造。为分析其物源,并对源区地壳生长和构造演化提供约束,本文对采自高滩组的变长石石英杂砂岩进行了LA-ICP-MS碎屑锆石U-Pb年代学和Hf同位素研究。锆石U-Pb年龄数据显示2 500 Ma、1 100~900 Ma和900~700 Ma 3个主要年龄峰值。2 500 Ma的年龄峰值代表了新太古代末期—古元古代的古陆核生长事件。1 100~900 Ma和900~700 Ma两个峰最显著,表明Rodinia超大陆聚合裂解在华南地区的响应,为该区寒武纪地层提供了主要物源。此外,3 003 Ma锆石年龄的捕获说明,华夏地块可能存在太古宙地壳基底。Hf同位素数据表明,源区锆石结晶多为古老地壳组分部分熔融产生的岩浆。结合锆石年龄数据分析认为,华南地区存在强烈的新元古代岩浆活动,该时期岩浆活动主要是古老地壳物质的再循环。     

北秦岭灵官庙盆地砂岩碎屑锆石LA-ICP-MSU-Pb年龄

秦岭造山带在印支造山作用主造山期之后,发育一系列晚三叠世—早侏罗世伸展断陷盆地。选择陕西丹凤北秦岭灵官庙盆地中低绿片岩相的灰绿色中细粒砂岩,进行碎屑锆石LA-ICP-MS U-Pb同位素分析。结果表明,85个以岩浆成因为主的碎屑锆石给出5个年龄组:426~605Ma、661~1174Ma、1494~1789Ma、2113~2261Ma和2826~3298Ma。其中,最年轻的锆石年龄为426Ma±5Ma,最老的锆石年龄为3298Ma±70Ma。主要的年龄峰期为426~605Ma年龄组,其次为661~1174Ma年龄组。这一年龄结构反映出物源区加里东造山期和Grenvillian期岩浆活动的重要影响。年龄谱中缺少中志留世—晚三叠世的锆石,说明普遍发育的印支期岩浆岩体并不构成物源区。通过与现今周缘地体年龄结构对比并结合其他地质证据认为,灵官庙盆地的物源可能主要来自加里东期侵位于二郎坪群、秦岭群中的花岗岩和新元古代宽坪群,少量来自二郎坪群和秦岭群。灵官庙盆地形成之后,盆地内沉积岩遭受了变质变形作用,记录了秦岭造山带在板块构造驱动的造山作用结束后进入了新的陆内造山作用阶段。     

云南格咱岛弧带休瓦促Mo W Cu矿床两期岩浆作用的锆石U Pb年龄、Hf同位素组成及构造意义

锆石LA-ICP-MS U-Pb定年结果显示,休瓦促Mo-W-Cu矿床含矿花岗闪长岩的形成年龄为202±3.5Ma,形成于甘孜-理塘洋壳向西俯冲时期;含矿二长花岗岩的形成年龄为83.3±1.7Ma,形成于燕山晚期造山后伸展环境。Hf同位素原位分析结果显示,花岗闪长岩中锆石的ε_(Hf)(t)值为-2.87~4.12(平均为0.09),T_(MD1)年龄541~828Ma,T_(DM2)年龄为719~1109Ma,表明岩体形成的物质来源除壳源物质之外,也有幔源物质的混入;二长花岗岩中锆石的ε_(Hf)(t)值为-7.96~-2.75(平均为-5.54),T_(MD1)年龄为820~1019Ma,T_(DM2)年龄为1102~1391Ma,ε_(Hf)(t)0,表明岩石是由古老地壳物质的部分熔融形成的产物。休瓦促两期含矿岩体的锆石U-Pb定年与Hf同位素原位分析显示,区内存在晚三叠世和晚白垩世两期构造-岩浆-成矿作用。晚三叠世花岗闪长岩岩浆侵入及Cu多金属成矿作用与洋壳俯冲造山有关;而晚白垩世二长花岗岩岩浆侵入及Mo多金属成矿作用主要形成于陆-陆碰撞造山的构造背景。研究表明,从晚三叠世洋壳俯冲造山至晚白垩世造山后伸展作用过程中都存在构造-岩浆-成矿作用的发生,且在晚三叠世构造-岩浆活动的基础上叠加了晚白垩世的成岩成矿作用,这为区内复合叠加成矿作用的研究提供了例证。     

西秦岭格娄昂金矿床赋矿斑岩岩石成因及其地质意义

西秦岭造山带广泛发育印支期花岗质岩石,已探明超过1200吨金资源量与这些花岗质岩石具有密切空间关系;揭示赋矿花岗质岩石成因对于进一步约束金成矿与岩浆作用是否具有成因关系具有重要意义。格娄昂矿床(金资源量27. 7t,平均品位2. 18g/t)是西秦岭造山带西段甘南地区的大型金矿床,花岗质岩石和变沉积岩是其主要赋矿围岩。格娄昂金矿床赋矿英安斑岩与黑云英安斑岩属于过铝质高钾钙碱性系列,轻重稀土分异较大,(La/Yb)N比值为31. 07～40. 59,富集大离子亲石元素,亏损高场强元素Nb、Ta等,具有弱铕负异常(δEu=0. 76～0. 78)。英安斑岩和黑云英安斑岩被金矿脉切割,LA-ICP-MS锆石U-Pb年龄分别为250. 8±2. 5Ma和252. 9±3. 4Ma,磷灰石U-Pb年龄分别为248. 9±7. 3Ma和249. 7±7. 9Ma,为成矿前早三叠世岩浆作用的产物。锆石εHf(t)=-13. 88～-7. 84,对应的二阶段Hf模式年龄(t_(DM)~2)为2. 15～1. 78Ga。因此,格娄昂金矿床早三叠世赋矿英安斑岩和黑云英安斑岩为成矿前岩浆活动的产物,源于古元古代下地壳的部分熔融。可能与洋壳板片北向俯冲有关,形成于活动大陆边缘碰撞前构造环境,进一步支持阿尼玛卿-勉略洋在早三叠世尚未闭合。     

湖南省东北部地区桃江县木瓜园钨多金属矿成岩成矿时代及其对区域成矿作用的启示

江南造山带的湘东北-赣西北-皖东南—浙西南地区存在一个北东向钨矿带,成因类型以斑岩型、矽卡岩型为主,近年在其西南方向新发现了木瓜园大型钨矿床,成矿过程与斑岩体密切相关。厘定了木瓜园矿区含矿花岗斑岩的锆石LA-ICP-MS U-Pb年龄(224.2±2.0)Ma(MSWD=0.65,n=17),辉钼矿Re-Os同位素等时线年龄(225.4±1.4)Ma(MSWD=0.71)及加权平均年龄(222.96±0.96)Ma(MSWD=1.08,n=5),表明矿区成岩与成矿时代均为晚三叠世,属于印支期;锆石初始176 Hf/177 Hf比值0.282 444～0.282 580,εHf(t)值为-1.9～-7.2,二阶段模式年龄(TDM2)为1 713～1 388Ma,表明含矿岩体岩浆源区主要为古元古代-中元古代古老地壳岩石,起源于下地壳古老物质的重熔。由于北东向钨矿带成岩成矿集中于燕山期,木瓜园成岩成矿集中于印支期,结合区域地质背景,推测该钨矿带西南方向不超过湘东北地区新宁-灰汤断裂,但湖南省东北部地区存在一次晚三叠世大规模成岩与局部钨钼多金属成矿过程,且具有较大的找矿潜力。     

西秦岭厂坝、黄渚关岩体的锆石U-Pb年龄、Hf同位素组成及其地质意义

厂坝及黄渚关岩体位于商丹缝合带和勉略缝合带之间的秦岭微板块,主要由花岗闪长岩及二长花岗岩组成。LA-MC-ICP-MS锆石U-Pb定年显示,黄渚关及厂坝岩体的演化可划分为中三叠世(229 Ma)和晚三叠世(215~209 Ma)2期。黄渚关中心部位的年龄((229.2±1.0)Ma)老于边部岩体((215.8±0.8)Ma),厂坝岩体中心部位年龄((218.3±1.2)Ma),老于边部年龄((209.4±0.8)Ma),结合岩体中心相和边缘相渐变的特征,说明2个岩体是由中心部位侵位,边部岩体的侵位冷却时间较晚造成的。黄渚关岩体的ε_(Hf)(t)为-3.13~-14.51,集中于-10~-6;厂坝岩体的ε_(Hf)(t)为-5.17~-14.51,集中于-12~-6。在ε_(Hf)(t)-t图解中,ε_(Hf)(t)均在球粒陨石之下和古元古地壳演化线之上;二阶段模式年龄黄渚关岩体主要集中在1.8~2.1 Ga,厂坝岩体主要集中在2.0~2.2Ga,结合继承锆石年龄1932 Ma、2039 Ma,表明古元古代地层可能为岩体的源区之一,在黄渚关岩体发现的暗色包体说明岩浆在上升的过程中发生了壳-幔岩浆的混合。因此,笔者认为黄渚关、厂坝岩体起源于古老地壳重熔,并在上升的过程中与幔源岩浆发生一定比例混合。     

The terrestrial fauna of the Late Triassic Pant-y-ffynnon Quarry fissures,South Wales,UK and a new species of Clevosaurus (Lepidosauria: Rhynchocephalia)

Pant-y-ffynnon Quarry in South Wales yielded a rich cache of fossils in the early 1950s, including articulated specimens of new species (the small sauropodomorph dinosaur Pantydraco caducus and the crocodylomorph Terrestrisuchus gracilis), but no substantial study of the wider fauna of the Pant-y-ffynnon fissure systems has been published. Here, our overview of existing specimens, a few described but mostly undescribed, as well as freshly processed material, provides a comprehensive picture of the Pant-y-ffynnon palaeo-island of the Late Triassic. This was an island with a relatively impoverished fauna dominated by small clevosaurs (rhynchocephalians), including a new species, Clevosaurus cambrica, described here from a partially articulated specimen and isolated bones. The new species has a dental morphology that is intermediate between the Late Triassic Clevosaurus hudsoni, from Cromhall Quarry to the east, and the younger C. convallis from Pant Quarry to the west, suggesting adaptive radiation of clevosaurs in the palaeo-archipelago. The larger reptiles on the palaeo-island do not exceed 1.5?m in length, including a small carnivorous crocodylomorph, Terrestrisuchus, and a possible example of insular dwarfism in the basal dinosaur Pantydraco.     

Définition d'une limite multicritère ; stratigraphie du passage Campanien–Maastrichtien du site géologique de Tercis (Landes,SW France)Definition of a multi-criteria boundary; stratigraphy of the Campanian–Maastrichtian interval of the geological site at Tercis (Landes,SW France)

Lithostratigraphy, physicochemical stratigraphy, biostratigraphy, and geochronology of the 77–70 Ma old series bracketing the Campanian–Maastrichtian boundary have been investigated by 70 experts. For the first time, direct relationships between macro- and microfossils have been established, as well as direct and indirect relationships between chemo-physical and biostratigraphical tools. A combination of criteria for selecting the boundary level, duration estimates, uncertainties on durations and on the location of biohorizons have been considered; new chronostratigraphic units are proposed. The geological site at Tercis is accepted by the Commission on Stratigraphy as the international reference for the stratigraphy of the studied interval. To cite this article: G.S. Odin, C. R. Geoscience 334 (2002) 409–414.     

The effect of water on accessory phase solubility in subaluminous and peralkaline granitic melts

The solubilities of columbite, tantalite, wolframite, rutile, zircon and hafnon were determined as a function of the water contents in peralkaline and subaluminous granite melts. All experiments were conducted at 1035 °C and 2 kbar and the water contents of the melts ranged from nominally dry to approximately 6 wt.% H₂O. Accessory phase solubilities are not affected by the water content of the peralkaline melt. By contrast, solubilities are affected by the water content of the subaluminous melt, where the solubilities of all the accessory phases examined increase with the water content of the melt, up to 2 wt.% H₂O. At higher water contents, solubilities are nearly constant. It can be concluded that water is not an important control of accessory phase solubility, although the water content will affect diffusivities of components in the melt, thus whether or not accessory phases will be present as restite material. The solubility behaviour in the subaluminous and peralkaline melts supports previous spectroscopic studies, which have observed differences in the coordination of high field strength elements in dry vs. wet subaluminous granitic glasses, but not for peralkaline granitic glasses. Lastly, the fact that wolframite solubility increases with increasing water content in the subaluminous melt suggests that tungsten dissolved as a hexavalent species.     

Quaternary stresses revealed by calcite twinning inversion: insights from observations in the Savonnières underground quarry (eastern France)

Calcite samples were extracted both from the rock matrix and the superficial coating of a karstified fault plane of an underground quarry, located in the eastern border of the Paris basin. The karstification is dated as Quaternary. Analysis of mechanical calcite twinning reveals that only the calcite matrix has also undergone a compression trending WNW that can be attributed to the Mio-Pliocene alpine collision. Both coating and matrix have undergone a strike-slip regime with σ₁ roughly trending north–south, that could correspond to the regional present-day state of stress, a strike-slip compression rather trending NNW, modified by local phenomena. To cite this article: M. Rocher et al., C. R. Geoscience 335 (2003).     

NONMETALS DEPOSITS

正20141520 Bo Ying(Key Laboratory of Metallogeny and Mineral Assessment,MLR,Beijing 100037,China);Liu Chenglin Saline Spring Hydrochemical Characteristics and Indicators for Potassium Exploration in Southwestern and Northern Tarim Basin,Xinjiang(Acta Geoscientica Sinica,ISSN1006-3021,CN11-3474/P,34(5),2013,p.594-602,5 illus.,3 tables,28 refs.)     

MATHEMATICAL GEOLOGY

正20141243Chen Ge(Hangzhou Research Institute of Petroleum Geology,PetroChina,Hangzhou 310023,China);Si Chunsong Study on Sedimentary Numerical Simulation Method of Fan Delta Sand Body(Journal of Geology,     

PROSPECTING EXPLORATION

正20142599Chen Sanming(Guangxi Key Laboratory of Concealed Deposits Exploration,Guilin University of Technology,Guilin541004,China);He Yuzhou Block Model and Reserves Estimation of Panzhihua Iron Deposit Based on 3D Geological Modeling(Journal of Guilin University of Technology,ISSN1674-9057,CN45-1375/N,33(4),2013,p.610-615,9illus.,1table,15refs.)     

STRUCTURAL GEOLOGY

正20140594 Bai Daoyuan(Hunan Institute of Geology Survey,Changsha 410016,China);Zhong Xiang Faults in the Jingzhou Basin and Their Tectonic Settings(Geotectonica et Metallogenia,ISSN1001-1552,CN44-1595/P,37(2),2013,p.173-183,6illus.,59refs.)Key words:basin evolution,tectonic setting,South China In the Upper Paleozoic and Jurassic se-     

STRUCTURAL GEOLOGY

正20141912Cao Hui(State Key Laboratory for Continental Tectonics and Dynamics,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China)Gravitational Collapse and Folding during Orogenesis:A Comparative Study of FIA Trends and Fold Axial Plane Traces(Geology in China,ISSN1000-3657,CN11-1167/P,40(6),2013,p.1818-1828,9illus.,35refs.,with