塔里木溢流玄武岩的喷发特征

通过对柯坪地区二叠系野外火山岩露头剖面和英买力、哈拉哈塘井区二叠系火山岩钻井剖面的对比,将塔里木早二叠世溢流玄武岩划分为三个旋回,从老到新依次是:库普库兹满溢流玄武岩旋回(KP),长英质火山碎屑岩旋回(FP)和开派兹雷克溢流玄武岩旋回(KZ)。KP旋回以巨厚溢流玄武岩夹凝灰岩为特征,在柯坪露头区和英买力井区均可划分出三层巨厚玄武质熔岩流,至哈拉哈塘井区减少为一层玄武岩流,但长英质火山碎屑岩和熔岩厚度增加。FP旋回在柯坪露头区自下而上包括空落相凝灰岩,熔结凝灰岩,再沉积火山碎屑岩和正常碎屑岩夹火山灰层,该层可与英买力及哈拉哈塘井区的凝灰岩层对比,表明在塔北存在一期面积广泛的长英质火山喷发。KZ旋回以溢流玄武岩为主,在开派兹雷克剖面识别出四期喷发共8层溢流玄武岩和一期安山质玄武岩,每期喷发之间夹少量碎屑岩,但未见长英质火山碎屑岩夹层,该特征与英买力和哈拉哈塘井区的火山层序组合不同,而与塔中溢流玄武岩类似。三个火山旋回的划分表明塔里木大火成岩省经历了"基性溢流玄武岩-酸性火山碎屑岩-基性溢流玄武岩"的演变过程,与Afro-Arabian溢流玄武岩省相似,可进行对比研究。     

古地理环境对火山喷发样式的影响:以准噶尔盆地玛湖凹陷东部下二叠统风城组为例

自然界中,火山的喷发样式常因岩浆或周围环境的变化而发生转换。为了探索沉积盆地古地理环境对古代火山喷发样式的可能影响,文中利用地震、钻测井及岩心资料,厘定准噶尔盆地玛湖凹陷东部下二叠统风城组古地理环境及火山岩的分布;利用岩心和薄片观察、扫描电镜、元素地球化学、电子探针等技术,对取心段火山岩岩石类型、岩石组合和地球化学特征开展了研究。结果表明:(1)取心段火山岩发育4种岩石类型和3种岩石组合,射气岩浆喷发和岩浆喷发2种火山喷发样式类型;(2)射气岩浆喷发以发育熔积岩,具面包皮结构、熔结结构、熔结珍珠结构的熔结凝灰岩和增生火山砾为特征,而岩浆喷发以胶结增生火山砾而形成含增生火山砾熔岩为特征;(3)火山口古地理环境的演化控制着火山喷发样式的类型及其转换,进而影响喷发产物的特征:古地理环境为水下环境时,足量的水和上升的高温岩浆相互作用发生射气岩浆喷发;古地理环境变为陆上时,岩浆发生溢流式岩浆喷发。取心段古地理环境变化的主要原因可能是喷发产物在火山口附近的堆积或季节性气候变化引起的湖平面变化;(4)古地理环境对古代火山喷发的样式类型、喷发过程、喷发产物特征具有重要影响,这可以为盆地中火山岩成因分析和喷发过程重建提供新的视角,为火山岩油气藏的精细勘探开发提供新的思路。     

古地理环境对火山喷发样式的影响:以准噶尔盆地玛湖凹陷东部下二叠统风城组为例*

自然界中,火山的喷发样式常因岩浆或周围环境的变化而发生转换。为了探索沉积盆地古地理环境对古代火山喷发样式的可能影响,文中利用地震、钻测井及岩心资料,厘定准噶尔盆地玛湖凹陷东部下二叠统风城组古地理环境及火山岩的分布;利用岩心和薄片观察、扫描电镜、元素地球化学、电子探针等技术,对取心段火山岩岩石类型、岩石组合和地球化学特征开展了研究。结果表明:(1)取心段火山岩发育4种岩石类型和3种岩石组合,射气岩浆喷发和岩浆喷发2种火山喷发样式类型;(2)射气岩浆喷发以发育熔积岩,具面包皮结构、熔结结构、熔结珍珠结构的熔结凝灰岩和增生火山砾为特征,而岩浆喷发以胶结增生火山砾而形成含增生火山砾熔岩为特征;(3)火山口古地理环境的演化控制着火山喷发样式的类型及其转换,进而影响喷发产物的特征:古地理环境为水下环境时,足量的水和上升的高温岩浆相互作用发生射气岩浆喷发;古地理环境变为陆上时,岩浆发生溢流式岩浆喷发。取心段古地理环境变化的主要原因可能是喷发产物在火山口附近的堆积或季节性气候变化引起的湖平面变化;(4)古地理环境对古代火山喷发的样式类型、喷发过程、喷发产物特征具有重要影响,这可以为盆地中火山岩成因分析和喷发过程重建提供新的视角,为火山岩油气藏的精细勘探开发提供新的思路。     

滇西南云县三叠纪火山岩组合及系列的厘定及其构造意义

本文重新厘定了云县三叠纪火山岩的组合和系列,识别了4个层位中的酸性熔结凝灰岩,重新划分了火山喷发旋回和韵律。中三叠统忙怀组(T_2m)为富硅富铝高钾流纹质火山岩组合,该旋回由5个喷发韵律层组成;上三叠统小定西组(T_3x)为高钾玄武岩-钾玄岩-安粗岩及火山碎屑岩组合,该旋回由6个喷发韵律层组成。芒汇河组(T_3mh)为钾质粗面玄武岩-高钾流纹质火山岩组合,该旋回由6个喷发韵律层组成。T_2m火山岩属碰撞型弧火山岩,T_3x和T_3mh火山岩属钾玄岩系列火山岩,具有滞后型弧火山岩之属性。     

中国北天山晚石炭世白杨沟火山岩的成因及地质意义

中国北天山作为中亚造山带西部重要的组成部分,其晚古生代的构造背景长期存在板内裂谷环境和岛弧环境两个截然不同的认识,有些学者还提出该地区有塔里木地幔柱的影响,从石炭纪到二叠纪均发育大量的双峰式火山岩。为了厘定其石炭-二叠纪模糊不清的构造属性以及火山岩的地质特征,本文对北天山博格达隆起带白杨沟地区火山岩进行了系统的研究。这套火山岩由枕状玄武岩、块状玄武岩、安山-英安质熔结凝灰岩、流纹岩和火山角砾岩组成。安山-英安质熔结凝灰岩和流纹岩属于Ⅰ型酸性岩,与枕状玄武岩及块状玄武岩整合接触。海相棘皮类化石的发现以及锆石SHRIMP U-Pb年龄(~311Ma)的测定指示这套白杨沟火山岩应属于晚石炭世祁家沟组。同时,安山-英安质熔结凝灰岩的发现表明白杨沟火山岩剖面并非双峰式火山岩,但与双峰式岩浆(玄武质和流纹质岩浆)有密切的成因关系。MELTS模拟计算指示白杨沟流纹岩和熔结凝灰岩不是与其共生的玄武岩高度结晶分异的产物。与含水玄武质岩石的部分熔融实验对比,正的ε_(Nd)(t)值(+5.9~+7.5)以及岛弧特征的微量元素性质则表明白杨沟流纹岩和熔结凝灰岩主要由含水的新生岛弧玄武质地壳(岩石)发生部分熔融形成。流纹岩很可能代表新生地壳部分熔融的直接产物。然而熔结凝灰岩中发育玄武质和长英质两类浆屑,大量斜长石晶屑的发育以及负Eu至正Eu异常(δEu=0.8~1.1)暗示安山-英安质熔结凝灰岩还受岩浆混合作用和长石堆晶作用的影响。结合博格达晚石炭世玄武岩的研究,本文认为博格达晚石炭世应为洋内岛弧后弧或弧后环境,与北天山洋(或称为准噶尔洋)向南俯冲有关。博格达隆起带石炭-二叠纪构造属性的转变很可能与东准噶尔弧和博格达弧在石炭-二叠纪界限时期发生的弧-弧碰撞作用有关。     

东川裂谷因民期火山——岩浆活动特征

东川裂谷因民期火山—岩浆活动强烈，也是重要的铁铜成矿期。火山活动旋回均经历爆发—喷发—喷溢—（喷流）阶段。主要发育在裂谷中心落因火山链和蓑衣坡火山盆地中。落因火山链早期形成火山—沉积角砾岩段，火山活动以喷溢的火山熔岩为主，主要有钠质基性熔岩、玄武岩、安山岩，均已蚀变，并有钠长斑岩的侵入活动。中期火山喷发形成凝灰岩类、火山碎屑岩类，发育了铁铜矿化。在蓑衣坡火山盆地中因民期火山—岩浆活动发育两次火山—沉积旋回，即两次爆发（角砾岩）—喷发（凝灰岩）—喷溢（熔岩）—喷流（硅质岩），在喷流相发育赤铁矿层和含铜硅质岩层。     

青海南部杂多地区新建扎青组的地层层序及地质意义

在青藏高原北羌塘盆地青海南部,青海省杂多县扎青乡地区的然者涌一带,发现以基性火山熔岩为主夹有中基性火山碎屑岩,具大陆板内裂谷拉斑玄武岩喷发特点的一套火山地层。该地层底部角度不整合接触覆盖在早中二叠世开心岭群诺日巴尕日保组、九十道班组之上,其上被晚三叠世结扎群甲丕拉组角度不整合覆盖。主要岩性为灰绿—灰紫色橄榄玄武岩、粗面玄武岩、玄武粗安岩及流纹岩、中基性火山角砾岩、角砾凝灰岩夹少量流纹岩和紫红色岩屑砂岩及细砾岩,其特征与峨眉山低钛玄武岩相似,具陆相喷发-沉积特征。区域对比在北羌塘地区具有独特地层特征,可与四川峨眉山玄武岩地层进行对比。而区域上该地区晚二叠世主要为一套海陆交互相含煤碎屑岩建造,未发现陆相火山岩出露,本文建立正式地层单位扎青组,以供参考,其时代暂归晚二叠—早三叠世。     

海南省海口地区第四纪火山盆地沉积特征

广泛分布于海南省北部的第四纪火山岩,至少有8次喷发活动。第一次发生在早更新世,沉积了凝灰岩、橄榄玄武岩,厚度为4.6～15.8m,它赋存于秀英组中,已测得热释光年龄为1999609±5988年。晚更新世道堂组有6次交替出现陆相与海相的基性火山熔岩及火山碎屑沉积岩的喷发活动,自下而上划分为四个段。其中一、三段为陆相喷发的橄榄拉斑、玄武岩、橄榄玄武岩,局部夹火山碎屑岩,厚度分别为49m和15～55m。第二、四段为海相玄武质岩屑,晶屑凝灰岩为主,含海绿石及有孔虫化石,厚度分别为129～150m、85m;第四段炭质粘上夹层测得~(14)C年龄为16790±410年。全新世早期的石山组,主要为橄榄拉斑玄武岩,熔渣—浮岩状橄榄玄武岩,底部偶见有含集块、火山角砾橄榄玄武岩,厚度>95m。     

福建寿山火山喷发盆地火山作用特征及与叶蜡石成矿关系探讨

寿山火山喷发盆地是福建东部晚中生代最重要的火山喷发盆地之一,是寿山石的产出地。福建1∶250 000周宁县等4幅区调项目通过系统剖面研究及路线调查认为,寿山火山喷发盆地由小溪组火山岩组成,划分为第一、二、三、四、五共5个岩性段;其构成一个完整的沉积-喷发旋回,根据综合地层接触关系、生物群等资料,将其形成时代置于早白垩世早期。查明该盆地火山岩相有8种类型,圈定17个Ⅴ级火山机构,明确小溪组第三段下部的流纹质(含)角砾凝灰岩及中部的(角砾)流纹岩、流纹质晶屑熔结凝灰岩为叶蜡石(寿山石)矿的主要含矿层位,矿体受火山构造控制明显。     

熔结凝灰岩成因研究日益深入

八十年代以来,由于热力学、流体动力学等知识的应用以及研究的定量化,使得熔结凝灰岩成因研究日益深入.1.成因类型划分愈来愈细至1979年,国内外学者已确认有爆发火山灰流成因的熔结凝灰岩、空降熔结火山碎屑岩(火雨成因)和熔结凝灰岩岩颈、岩墙、岩脉.进入八十年代,随着对熔结凝灰岩地质特征和岩性特征的更加深入细致的研究,其它一些成因观点或假说不断提出,可归纳如下:(1)喷溢泡沫灰流成因;(2)熔离成因;(3)玻质熔岩重融成因;(4)作为碎斑花岗岩边缘相产状.其中喷溢泡沫灰流成因已得到确认,它与爆发火山灰流成因机理不同之处在于,岩浆发泡作用较强而喷发时爆炸力较弱.对后三种观点仍有异议,(2)、(3)二种观点所指的岩石,简述如下:熔离成因是指岩浆在地下由于熔离作用形成各种形态的熔离体,然后含有熔离体的岩浆喷溢至地表,熔     

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.     

Late Wuchiapingian (Late Dzhulfian,early Late Permian) limestone olistolites within the Tertiary flysch of Glypia Unit (Mount Parnon,central–eastern Peloponnesus,Greece)

Some olistolites reworked in a Tertiary flysch of Mount Parnon (Peloponnesus, Greece) exhibit a Late Permian assemblage, dominated by Paradunbarula (Shindella) shindensis, Hemigordiopsis cf. luquensis and Colaniella aff. minima. This association corresponds to the Late Wuchiapingian (=Late Dzhulfian), a substage whose algae and foraminifera are generally little known. Contemporaneous limestones crop out in the middle part of the Episkopi Formation in Hydra, but they are rather commonly reworked in Mesozoic and Cainozoic sequences. The palaeobiogeographical affinities shared by the foraminiferal markers of Greece, southeastern Pamir, and southern China, are very strong (up to the specific level), and are congruent with the Pangea B reconstructions. To cite this article: E. Skourtsos et al., C. R. Geoscience 334 (2002) 925–931.     

PALEONTOLOGY

正20141596 Liu Yunhuan(School of Earth Sciences and Resources,Chang’an University,Xi’an 710054,China);Shao Tiequan Early Cambrian Quadrapyrgites Fossils of Xixiang Boita in Southern Shaanxi Province(Journal of Earth Sciences and Environment,ISSN1672-6561,CN61-1423/P,35(3),2013,p.39-43,3 illus.,20 refs.)     

GEOCHEMICAL EXPLORATION

正20141719 Chen Zhijun(State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Wuhan 430074,China);Chen Jianguo Automated Batch Mapping Solution for Serial Maps:A Case Study of Exploration Geochemistry Maps(Journal of Geology,ISSN1674-3636,CN32-1796/P,37(3),2013,p.456-464,2 illus.,2 tables,10 refs.)     

MICROPALAEONTOLOGY

正20140962 Chen Fenning(Xi’an Institute of Geology and Mineral Resources,Xi’an710054,China);Chen Ruiming Late Miocene-Early Pleistocene Ostracoda Fauna of Gyirong Basin,Southern Tibet(Acta Geologica Sinica,ISSN0001-5717,CN11-1951/P,87(6),2013,p.872-886,6illus.,56refs.)     

PETROLOGY

正1.IGNEOUS PETROLOGY20142008Cai Jinhui(Wuhan Center,China Geological Survey,Wuhan 430205,China);Liu Wei Zircon U-Pb Geochronology and Mineralization Significance of Granodiorites from Fuzichong Pb-Zn Deposit,Guangxi,South China(Geology and Mineral Resources of South China,ISSN1007-3701,CN42-1417/P,29(4),2013,p.271-281,7illus.,     

ENVIRONMENTAL GEOLOGY

正20141205Cheng Weiming(State Key Laboratory of Resources and Environmental Information System,Institute of Geographic Sciences and Natural Resources Research,CAS,Beijing 100101,China);Xia Yao Regional Hazard Assessment of Disaster Environment for Debris Flows:Taking Jundu Mountain,Beijing as an