小秦岭大湖金钼矿床辉钼矿铼锇同位素年龄及印支期成矿事件

东秦岭北部存在世界最大的钼矿带,并蕴涵著名的小秦岭造山型金矿田,金、钼矿床成矿时代和构造背景一直存在争议。河南小秦岭金矿田大湖金矿床深部新发现了石英脉型钼矿床,查明钼资源储量已达中型。6件辉钼矿样品Re-Os同位素模式年龄介于215.4±5.4～255.6±9.6Ma,等时线年龄为218±41Ma(2σ误差,MSWD=38),加权平均年龄为234±18Ma(2σ误差,MSWD=23),表明钼矿化发生在印支期。结合对已有年龄资料的归纳和分析,认为秦岭造山带曾在印支期发生重要的岩浆-成矿事件,但被燕山期造山作用所改造或破坏,在秦岭造山带北缘尚有明显保留或记录。     

东秦岭中生代成矿规律研究的几点新认识

1 小秦岭金成矿区最近发现石英脉型金钼矿化,其成矿时代为印支期和燕山期 小秦岭是我国著名的金矿集中区.金矿的成矿时代为燕山期,较精确的年龄为黑云母及绢云母的Ar-Ar年龄(126.9±0.3)Ma～(132.16±2.64)Ma(王义天等,2002;徐启东等,1998).小秦岭金矿集中区南侧为著名的金堆城钼矿区,钼矿化除主要发生于燕山期外,也有印支期的:金堆城斑岩型钼矿床的辉钼矿Re-Os年龄为(127±7)Ma～(141±4)Ma(黄典豪等,1994;杜安道等,1994;Stein等,1997),黄龙铺碳酸岩脉型钼(铅)矿床中辉钼矿Re-Os年龄为(216±2)Ma～(222±4)Ma(黄典豪等,1994;杜安道等,1994;Stein等,1997).     

小秦岭北缘马家洼石英脉型金钼矿床的辉钼矿Re-Os年龄及其意义

马家洼金钼矿床位于小秦岭北缘,矿体发育在由近东西向脆韧性断裂构造带控制的石英脉中。对该矿床辉钼矿样品进行的Re-Os同位素年代学研究表明:模式年龄范围是232.5～268.4 Ma,等时线年龄为(232±11)Ma,即钼成矿作用时代为早、中三叠世。辉钼矿样品的Re含量范围是(0.474～0.791)×10~(-6),初始~(187)Os/~(188)Os比值为2.4±6.4,Re-Os同位素组成特征指示了成矿物质主要来源于地壳。马家洼石英脉型金钼矿床是区域伸展体制下构造-流体成矿事件的产物。在华北板块南缘太古宙基底岩系中的脆韧性断裂构造带中寻找印支期和燕山期石英脉型金钼矿床和钼矿床是一个新的找矿方向。     

大别山南麓梨木岭钼矿床辉钼矿Re-Os同位素年龄及地质意义

梨木岭钼矿床是近年来新发现的钼矿,也是目前大别山构造带唯一具有工业意义的中型钼矿床。通过辉钼矿Re-Os同位素年代学测定,获得梨木岭钼矿Ⅰ矿脉5件样品辉钼矿的Re-Os模式年龄为(115.3±1.4)Ma~(118.1±1.5)Ma,加权平均年龄为(116.8±1.3)Ma;等时线年龄为(119.9±6.2)Ma(MSWD=1.6)。Ⅱ矿脉2件辉钼矿Re-Os模式年龄分别为(114.7±1.6)Ma和(117.0±1.4)Ma。两条矿脉中辉钼矿样品的Re-Os模式年龄在误差范围内一致,表明这两条矿脉为早白垩世同期热液产物。梨木岭钼矿床可能为与早白垩世中酸性岩浆活动有关的岩浆热液型矿床。早白垩世大别山钼成矿作用不仅仅局限在北大别的北淮阳构造带,在大别山南麓同样存在该阶段钼成矿作用。     

粤北大宝山矿区船肚钼矿床辉钼矿Re-Os年龄及其地质意义

船肚钼矿床是近期在大宝山矿区内发现的大型矽卡岩型钼矿床,对辉钼矿样品进行了Re-Os同位素分析,获得辉钼矿Re-Os同位素模式年龄范围为(163.3±2.5)Ma~(165.2±2.3)Ma,等时线年龄为(165.8±9.2)Ma(MSWD=0.80),表明其形成于中侏罗世,与大宝山石英脉型辉钼矿年龄相一致,同属华南中生代大规模成矿作用的第一成矿阶段(170~150 Ma),是华南中生代大规模岩石圈伸展—减薄背景下的产物。     

东秦岭寨凹钼矿床辉钼矿Re-Os同位素年龄及熊耳期成矿事件

河南寨凹钼矿床位于东秦岭钼矿带,是近年来新发现的脉状钼矿床.9件辉钼矿样品Re-Os模式年龄介于1603.1±10.8～2031.9±10.2Ma,其中7件样品给出了精确的等时线年龄为1762±31Ma(1σ误差,MSWD=3.6),模式年龄的加权平均值为1753±26Ma(1σ误差,MSWD=3.2),表明寨凹钼矿形成于古元古代或熊耳期,代表着～1.76Ga左右的钼成矿事件.根据区域地质演化,认为寨凹钼矿形成于与熊耳群弧火山岩建造相当的活动大陆边缘岩浆弧背景.寨凹矿床的发现表明,熊耳期成矿事件虽遭受后期多次增生和碰撞造山作用的改造和破坏,但仍可在秦岭造山带最北部保留.     

西秦岭西成矿集区厂坝岩体的钼矿化特征及其Re-Os年龄

甘肃西成矿集区是西秦岭最重要的多金属成矿区之一,以铅锌矿床为主,其次发育有金、铜、钼等矿床(点)。厂坝黑云母二长花岗岩体位于西成矿集区中东部,岩体南缘接触带部位发育石英脉型钼矿,辉钼矿呈中粗粒半自形团块状产于粗粒石英脉内。Re-Os同位素年代学研究表明,其模式年龄范围为207.7±3.0~209.8±2.8Ma,加权平均年龄为208.9±1.1 Ma,等时线年龄为209±15 Ma,指示钼矿化发生于晚三叠世。辉钼矿的铼含量介于18.82×10~(-6)~21.97×10~(-6)之间,平均19.65×10~(-6),表明成矿物质主要为壳幔混合来源,可能以壳源为主。钼矿化与区域岩浆活动以及金、铅锌成矿作用时代相近,是印支期区域构造-岩浆-流体活动的产物。钼矿化年龄的厘定为区内找矿提供了新的思路。     

赣南樟东坑钨矿两类矿化中辉钼矿的Re-Os同位素定年及其地质意义

赣南樟东坑钨矿具有典型的"上脉(黑钨矿石英脉)下体(蚀变细粒花岗岩)"和"上钨下钼"矿化模式,为了弄清黑钨矿石英脉与蚀变细粒岩体型矿化之间在成矿时间上的关系,对产于该矿细粒花岗岩中的辉钼矿和石英脉中的辉钼矿分别进行了Re-Os同位素定年.测试结果为:细粒花岗岩中的3件辉钼矿样品Re-Os等时线年龄为155.4±2.1Ma(MSWD=1.12),模式年龄154.9±2.6Ma~156.5±2.6Ma,加权平均年龄155.5±1.4Ma(MSWD=0.44);而石英脉中5件辉钼矿样品的Re-Os等时线年龄为154.6±1.7Ma(MSWD=0.030),模式年龄变化范围为154.2±2.3Ma~154.7±2.7Ma,加权平均年龄为154.29±0.98Ma(MSWD=0.045).上述结果表明,花岗岩体型矿化与石英脉型矿化的年龄在误差范围内高度一致,从而证明了岩体中的钼钨矿化与石英脉中的钨钼矿化为同一次岩浆热液矿化事件的产物.     

赣南樟东坑钨矿两类矿化中辉钼矿的Re-Os同位素定年及其地质意义

赣南樟东坑钨矿具有典型的"上脉(黑钨矿石英脉)下体(蚀变细粒花岗岩)"和"上钨下钼"矿化模式, 为了弄清黑钨矿石英脉与蚀变细粒岩体型矿化之间在成矿时间上的关系, 对产于该矿细粒花岗岩中的辉钼矿和石英脉中的辉钼矿分别进行了Re-Os同位素定年. 测试结果为: 细粒花岗岩中的3件辉钼矿样品Re-Os等时线年龄为155.4±2.1 Ma(MSWD=1.12), 模式年龄154.9±2.6 Ma~156.5 ± 2.6 Ma, 加权平均年龄155.5±1.4 Ma(MSWD=0.44);而石英脉中5件辉钼矿样品的Re-Os等时线年龄为154.6±1.7 Ma(MSWD=0.030), 模式年龄变化范围为154.2±2.3 Ma~154.7±2.7 Ma, 加权平均年龄为154.29±0.98 Ma(MSWD=0.045). 上述结果表明, 花岗岩体型矿化与石英脉型矿化的年龄在误差范围内高度一致, 从而证明了岩体中的钼钨矿化与石英脉中的钨钼矿化为同一次岩浆热液矿化事件的产物.      

豫西熊耳山寨凹钼矿床辉钼矿铼-锇年龄及其地质意义

寨凹钼矿床位于河南熊耳山地区,是新近发现的穿插于太古宙太华岩群深变质岩中的辉钼矿石英脉型钼矿床.为了获得该钼矿床的成矿年龄,从10件采自辉钼矿石英脉的样品中挑选出辉钼矿单矿物进行Re-Os同位素年龄测定.10件辉钼矿样品22次测定结果的年龄最小值为(1 680±24)Ma,最大值为(1 831±29)Ma.其中10件辉钼矿粗粒(自然粒度)状态下13次测定结果的等时线年龄为(1 686±67)Ma,MSWD=16;4件研磨后粉末状辉钼矿9次测定结果的等时线年龄为(1 804±12)Ma,MSWD=1.09.两条等时线的仞始<'187>Os值在误差范围内接近于0,表明<'187>Os全部由Re衰变而来.上述结果表明,寨凹钼矿床形成于17～18亿年的中元古代早期,是目前中国已知最老的钼矿床,为中元古代早期华北克拉通伸展-裂解环境中构造-岩浆热事件所伴随的热液成矿作用的产物,与熊耳群火山岩浆活动有密切的时空和成因联系;辉钼矿的Re含量为4.832×10<'-6>～0.665×10<'6>,平均3.045×10<'-6>,表明成矿物质可能来自围岩地层.东秦岭地区从元古宙到印支期、燕山期的铜矿化构成该区的钼成矿谱系,寨凹钼矿床可能是该谱系中最早的端员.     

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).     

HYDROGEOLOGY

正20141756 Chen Ruige(Mathematical College,China University of Geosciences,Beijing100083,China);Zhou Xun Numerical Simulation of Groundwater Level Fluctuation in a Coastal Confined Aquifer with Sloping Initial Groundwater Level Induced by the Tide(Geological Bulletin of China,ISSN1671-2552,CN11-4648/P,32(7),2013,p.1099-1104,6 illus.,16 refs.) Key words:confined water,groundwater level     

METAMORPHIC PETROLOGY

正20141408 Cai Jia(Institute of Geology,Chinese Academy of Geological Sciences,Beijing100037,China);Liu Fulai Petrogenesis and Metamorphic P-T Conditions of Garnet-Spinel-Biotitebearing Paragneiss in Danangou Area,Daqingshan-Wulashan Metamorphic Complex Belt(Acta Petrologica Sinica,ISSN1000-0569,CN11-1922/P,29(7),     

SERIALS

正~~     

GEOPHYSICAL EXPLORATION

正20142386An Guoying(China Aero Geophysical Survey and Remote Sensing Center for Land and Resources,Beijing 100083,China)Application of Satellite Remote Sensing in Regional Hydrogeological Investigation:Taking Cenozoic Strata in Wenquan Sheet(1∶250 000)of Karakoram Range as an Example(Geosci-     

QUATERNARY GEOLOGY & GEOMORPHOLOGY

正20141016An Chengbang(Key Laboratory of Western China’s Environmental Systems,Ministry of Education,Lanzhou University,Lanzhou 730000,China);Zhao Yongtao Lake Records during the Last Glacial Maximum from Xinjiang,NW China and Their Climatic Impli-     

PETROLEUM GEOLOGY

正20141538 Cao Qing(School of Earth Sciences and Engineering,Xi’an Petroleum University,Xi’an 710065,China);Zhao Jingzhou Characteristics and Significance of Fluid Inclusions from Majiagou Formation,Yichuan Huangling Area,Ordos Basin(Advances in Earth Science,ISSN1001-8166,CN62-1091/P,28(7),2013,p.819-828,7 illus.,3 tables,43 refs.)