松辽盆地新生代构造演化对砂岩型铀矿成矿的控制作用——来自磷灰石裂变径迹的证据

本文针对松辽盆地北部隆起区的4个钻孔13件样品系统展开了磷灰石裂变径迹测试,揭示了松辽盆地新生代构造演化对砂岩型铀矿床的限制作用。13件磷灰石裂变径迹测试结果表明,松辽盆地北部晚白垩世以来的构造演化过程主要经历了3期快速隆升事件:(1)晚白垩世—始新世(71～48 Ma),期间以8～56 m/Ma的平均速率隆升,盆地北部整体呈抬升状态;(2)早渐新世—中新世(36～18 Ma),期间以24～49 m/Ma的平均速率隆升,盆地北部呈差异性抬升过程,第二期抬升事件隆升强度和持续时间较第一期抬升事件略低;(3)中新世-至今(18～0 Ma),期间以2～19 m/Ma的平均速率隆升,盆地北部缓慢抬升,构造活动较弱,三期构造抬升事件与太平洋板块俯冲速率和方向转向密切相关。结合前人低温热年代学数据,针对南部地区钱家店铀矿床成矿年代学成果研究发现,新生代以来的构造抬升事件伴生其后均成藏有砂岩型铀矿,砂岩型铀成矿与新生代构造密切相关,尤其与中新世末次隆升事件紧密相关,成矿过程延续至今。     

云南中甸地区晚白垩世斑岩型Mo-Cu矿床磷灰石、锆石裂变径迹年代学研究

云南中甸地区位于西南三江铜钼铅锌金多金属矿集区的南端,是一个独具特色的Cu-Mo多金属复合叠加成矿带.本文采用裂变径迹低温热年代学技术对区内晚白垩世铜厂沟、休瓦促、热林成矿斑岩体,进行了锆石、磷灰石裂变径迹分析测试,开展了晚白垩世以来的构造热史演化模拟,揭示了区内构造-岩浆成矿事件及热史演化过程.研究表明,锆石裂变径迹年龄值变化于52±2～96±5 Ma;磷灰石裂变径迹的年龄值变化于15±1～48±3 Ma,总体变化幅度不大,中心年龄与池年龄在误差范围也基本一致.通过锆石、磷灰石的裂变径迹分析,揭示出云南中甸地区自晚白垩世以来主要经历了三个阶段的构造热事件.第一阶段(96～60 Ma),主要为岩浆侵位后快速降温的热史演化阶段;第二阶段(52～39 Ma),为缓慢的降温作用过程;第三阶段(16～15 Ma),揭示了受中新世以来青藏高原隆升造山作用的影响,该区经历了快速降温的地质演化过程.综合锆石裂变径迹、磷灰石裂变径迹的热史反演结果,表明区内晚白垩世典型成矿斑岩体具有相似的隆升过程和剥蚀历史,并获得了剥蚀量与剥蚀速率的定量计算结果,为区内矿床的资源潜力评价及勘查工作提供了科学参考.     

塔北中新生代构造演化与砂岩型铀成矿作用关系——来自磷灰石裂变径迹的证据

塔里木盆地北部萨瓦甫齐及塔里克地区4个样品的磷灰石裂变径迹测年以及热史反演结果显示,两个地区的隆升时代不同,其中萨瓦甫齐地区裂变径迹年龄为3．5～3．9Ma,而塔里克地区的裂变径迹年龄为53～59Ma。热史分析揭示出岩体至少记录了自晚白垩世以来的3个显著冷却阶段。同时,结合前人对塔北中新生代隆升剥蚀研究结果,重点对塔北地区中新生代构造隆升阶段进行了详细研究与划分,结合新疆中新生代砂岩型铀成矿年龄,提出了对塔北地区中新生代构造演化与砂岩型铀成矿作用的新认识。     

伊犁盆地南缘构造活动及对砂岩型铀矿的制约:来自磷灰石裂变径与U-Pb定年的证据

为了探讨伊犁盆地南缘构造活动与铀成矿关系,通过采取砂岩型铀矿含矿层砂岩样品,利用磷灰石裂变径迹热年代学与U-Pb等时线定年的方法,对伊犁盆地南缘构造活动与砂岩型铀矿成矿年龄进行了研究。研究结果表明：①伊犁盆地南缘自中生代以来经历了三期强烈的隆升—剥蚀事件,三叠纪末—中侏罗世、晚侏罗世—早白垩世、中新世—现今,对应印支末期、燕山期与喜马拉雅期三期构造活动;②盆地南缘中—西段砂岩型铀矿成矿年龄可分为158~153 Ma、108~60.5 Ma、55~15 Ma,12~0.3 Ma四期,盆地东段铀成矿年龄比较新,为7.8~5.5 Ma之间;③盆地南缘构造活动时间与铀成矿年龄具有非常好的对应性,将伊犁盆地南缘铀成矿作用过程划分为三个阶段,物源区快速抬升—含矿建造形成期及铀的预富集阶段、主成矿阶段、后生叠加改造阶段。     

松辽盆地北部构造演化对砂岩型铀矿床成矿的控制作用

松辽盆地构造演化划分为前中生代克拉通基底演化、晚侏罗世挤压火山穹窿演化、早白垩世伸展断陷、晚白垩世早期热冷却坳陷、晚白垩世晚期反转褶皱隆升萎缩剥蚀、古近纪伸展断陷隆升剥蚀及新近纪—第四纪挤压坳陷等7个演化阶段。本文系统讨论了松辽盆地北部构造演化与铀成矿作用的关系,指出晚白垩世早期冷却坳陷、晚白垩世晚期反转褶皱隆升萎缩剥蚀、古近纪伸展断陷隆升剥蚀3个阶段为区内主要铀成矿阶段。铀矿化的分布受基底断裂及反转构造带联合控制。松辽盆地北部构造演化对各构造分区铀矿床成矿类型具有明显的控制作用：西部斜坡区以寻找"古层间氧化"型、层间氧化型砂岩型铀矿床为主要类型;中央坳陷区及东北隆起区应围绕大庆长垣、绥棱背斜带等构造剥蚀天窗寻找"钱家店"式砂岩型铀矿床;北部倾没区及东北隆起区盆缘以寻找层间氧化型砂岩型铀矿床为主要类型。     

地质构造演化对砂岩型铀矿成矿控制作用——以新疆库米什盆地为例

库米什盆地为中新生代叠合盆地,构造演化经历了拉张断坳(T3-J2)、挤压隆升(J3-K2)、区域沉降(E-N1)、挤压走滑(N2-Q)四个阶段.在铀成矿历史中,构造运动通过改造目的层,影响地下水动力状况,进一步控制层间氧化带的发育和铀矿化形成.分析认为:库米什盆地层间氧化带发育经历了古层间氧化带和新构造运动以来的现代层间氧化带两个阶段,与之相关的铀矿化亦经历了初始铀矿化阶段和再富集两个阶段.该区是铀成矿的有利地段,构造演化与砂岩型铀成矿关系的分析对天山中部中新生代盆地铀矿找矿具有借鉴意义.     

西藏冈底斯带南木林地区构造活动的磷灰石裂变径迹分析

南木林地区属于冈底斯地块的南带,研究样品取自不同时代的火山岩地层,本文报道应用磷灰石裂变径迹热年代学研究构造活动的新成果.总计获得5个样品的磷灰石裂变径迹分析结果,其中3个样品属于同组年龄,分别为5.9±0.7Ma,5.2±0.6 Ma和8.7±1.0Ma,平均径迹长度为13.0～13.2±2.2μm,并呈单峰分布,表明它们是最近一次构造热事件的体现.另2个样品属于混合年龄,系由7.1Ma、30Ma、9.6Ma、51Ma和100Ma等5组年龄组成.所有这些年龄值.先后与区内_碰撞前、同碰撞、碰撞后和陆内快速隆升作用有关.自印度-亚洲大陆强烈碰撞以来,总体上具有2阶段热演化历史,其中6～0Ma期间冷却速率为11.3℃～16.7℃/Ma,隆升速率为0.85～0.99mm/a,总计隆升幅度达5100～5940m.是本区冷却隆升的主要时期.     

青藏高原东部中新生代差异隆升的热年代学证据

为定量分析青藏高原东北部中新生代以来构造隆升时序及特征,笔者开展了磷灰石和锆石裂变径迹年龄测试。结果表明：研究区磷灰石裂变径迹年龄为(66±9)～(4.3±1) Ma,锆石裂变径迹年龄为(187±11)～(69±4) Ma,东北部及东部裂变径迹年龄值较大;研究区西北缘构造隆升较早(200～160 Ma),东南部隆升相对较晚(140～30 Ma),西(南)部构造隆升最晚(90～10 Ma),新近纪之后则整体进入构造隆升;岩石冷却速率和剥蚀速率广元—江油一带西侧较高,红原—文县一带南侧更高,理县附近最大,分别为23.26℃/Ma和0.78 mm/a,这种分区差异性主要受多条区域性大型断裂带制约。     

准东构造隆升对砂岩型铀成矿作用的制约:磷灰石裂变径迹证据

通过实测磷灰石裂变径迹方法,并结合前人研究结果,分析了准东构造隆升特征,探讨了其与地层沉积、构造响应及对砂岩型铀成矿的制约.研究表明,210~180 Ma,准东缘卡拉麦里地区持续隆升遭受剥蚀,而卡拉麦里山北部奥克什山地区隆升-剥蚀时间相对较晚,于160~80 Ma快速隆升,该期快速隆升控制了五彩湾-老君庙-将军庙与卡姆斯特地区沉积地层发育、古水流方向、区域不整合与构造掀斜等,从而控制着2个地区的砂岩型铀矿成矿条件.五彩湾-老君庙-将军庙地区下侏罗统物源充足、砂体与氧化发育,是该地区主要找矿目的层,而卡姆斯特地区随着晚侏罗世-晚白垩世,盆地东北部奥克什山乃至青格里底山的隆升,增加了物源供给,下侏罗统沉积地层在该地区表现出了更好的成矿潜力.      

川西北碧口地块中新生代隆升及构造扩展特征

青藏高原东北缘的向东构造扩展特征是地质热点问题之一,为了精确厘定该扩展速率及变化特征,本文对碧口地块及其东西两侧地层的磷灰石和锆石样品开展了裂变径迹测定和分析。结果表明：磷灰石裂变径迹长度在11.5 ~ 12.6 μm之间,绝大部分磷灰石和锆石裂变径迹年龄分别为古近纪（66.9 ~ 45.4 Ma）和侏罗纪—早白垩世（201.5 ~ 105.9 Ma）。研究区热史演化总体上具有阶段性,其中碧口地块构造隆升具一致性,而东侧地区热史演化相似且明显滞后于碧口地块,即碧口地块在27 ~ 15 Ma之间急剧隆升,而东侧区域不同位置随后在12 Ma和4 Ma开始发生急剧构造隆升。这种构造隆升时间差异是因为碧口地块在随青藏高原地块向东南构造挤压过程中,构造应力向东南方向传递且发生构造扩展所致,构造扩展速率由西至东递减显著,由碧口地块内部的20 km/Ma逐渐降至四川盆地边缘的1.40 km/Ma。构造扩展速率受到地层岩性及构造变形样式等多种因素影响,碧口地块内部的构造扩展速率大约是东侧区域的12 倍,构造扩展至四川盆地边缘逐渐减弱并在盆地内消失。     

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.     

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

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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.)     

GEOCHEMISTRY

正20142002 Wei Hualing(Institute of Geophysical and Geochemical Exploration,Chinese Academy of Geological Sciences,Langfang065000,China);Zhou Guohua Element Content and Mineral Compositions in Different Sizes of Soil in Tongling Area,Anhui Province(Geological Bulletin of China,ISSN1671-2552,CN11-4648/P,32(11),2013,p.1861