内蒙古阿鲁科尔沁旗新民组“豆状”凝灰岩岩石学特征及成因探讨   总被引：1，自引：0，他引：1  

钟辉  郜晓勇  伍月 《地质与资源》2016,25(2):121-124

内蒙古阿鲁科尔沁旗新民组出露有“豆状”凝灰岩,其中含“火山豆”（火山灰球）65%左右.“火山豆”发育同心韵律环带构造,有的发育有玻璃质边,有的可见长石晶屑嵌入其边缘,填隙物中可见有长石晶屑聚集现象.通过分析岩石结构及碎屑成分特征,认为“火山豆”凝灰岩是火山喷发过程中,由炽热的高能量高密度火山灰涌流向外迁移并伴随大气降水共同作用形成.  相似文献   

Volcano-sedimentary stratigraphy in the Valsequillo Basin,Central Mexico inferred from electrical resistivity soundings     

《Geofísica Internacional》2014,53(1):87-94

Initial results of an electrical resistivity survey of the volcano-sedimentary sequence of the Valsequillo basin in central Mexico are presented. The volcano-sedimentary deposits preserve rich paleontological, paleoclimatic and paleoenvironmental records, which include extinct megafauna remains associated with human artifacts. The report of possible 38 ka old human footprint tracks in the Xalnene tuff attracted renewed interest in the basin stratigraphy. We examine the shallow stratigraphic sequence in the Xalnene tuff outcrop plain northwest of Cerro Toluquilla volcano using vertical resistivity soundings (VES). Inversion models of VES soundings show a layered structure of high and low resistivity units, which characterize the Xalnene tuff, lacustrine and fluvial sediments and volcanic rocks. 2-D resistivity cross sections document three major units corresponding to the Xalnene tuff and sediments filling a <30 m deep basin lying on volcanic rocks. Resistivity models provide further support for the association of Xalnene tuff with the Toluquilla volcano and emplacement of the pyroclastic deposits on a shallow lacustrine environment. The resistivity cross sections constrain the thickness of the tuff layers and underlying lacustrine sediments. Observations during the data acquisition field work provide insight on the possible origin of the apparent tracks, which seem to develop from erosion processes acting on quarrying marks. Further analysis and experimental evidence is required to understand the morphology and weathered patterns. The tuff layers are being removed by quarrying operations and the outcrops significantly altered. Adequate conservation measurements should be implemented to preserve the deposits for scientific research.  相似文献   

Zircon SHRIMP U-Pb age and geological implications of tuff at the bottom of Chang-7 Member of Yanchang Formation in the Ordos Basin   总被引：2，自引：0，他引：2  

WANG DuoYun  XIN BuShe  YANG Hua  FU JinHua  YAO JinLi  ZHANG Yu 《中国科学:地球科学(英文版)》2014,(12)

A table tuff interlayer at the bottom of Chang-7 Member of Yanchang Formation,the Ordos Basin,may serve as an indicator for stratigraphic division and correlation.In this study,zircon SHRIMP U-Pb dating was performed on the tuff at the bottom of Chang-7 Member using samples from wells Luo-36 and Zhuang-211 in the southwest of the basin,which yielded weighted average 206Pb/238U ages of 241.3±2.4 and 239.7±1.7 Ma,respectively.The cathodoluminescence images and the U/Th element ratio of tuff indicate that the zircons are magmatogenic and their ages represent that of the sedimentation age of the tuff at the bottom of Chang-7,which is 239.7–241.3 Ma in age.This finding confirms presence of the Middle Triassic strata at the bottom of Yanchang Formation.Taking previous findings into account,we suggest restricing the Late Triassic Yanchang Formation sensu stricto to the interval from Chang-7 to Chang-1 and assigning the interval from Chang-10 to Chang-8 as the Tongchuan Formation.The tuff at the bottom of the Chang-7 Member of Yanchang Formation represents the sedimentary response to the Qinling orogenic event in the early Indosinian.This tectonic event resulted in major changes in paleogeomorphology and the sedimentary environment of the lake basin during deposition of the Yanchang Formation.During this period,extremely favourable conditions were present for subsequent hydrocarbon generation and pooling of lake basin.  相似文献   

内蒙古二连盆地凝灰岩潜山多期风化壳形成及油气成藏效应          下载免费PDF全文

李浩  高先志  杨德相  王会来  王苗 《高校地质学报》2014,20(1):114-121

火山喷发的多期性是导致凝灰岩潜山纵向多期风化壳(带)发育的重要原因。从地球化学、测井响应特征和岩石学 证实了二连盆地凝灰岩潜山多期风化壳(带)的存在及其特征:(1)哈31井凝灰岩地层在1062~1080 m和1165~1179 m两 个井段表现为 K,Na,Ca 等元素淋滤,CIA 指数较大,而 Al,Fe,Mn,P 等元素相对富集,S/A 指数变小;(2)这两个层段 测井响应表现为风化壳的特征,而且其测井曲线在纵向上具旋回特征并有连井上的可对比性;(3)不同喷发期次形成的凝 灰岩结构、组分以及粒度不同。凝灰岩潜山多期风化壳(带)的存在对潜山油气藏的形成具有重要作用,成藏效应主要表 现在储集层垂向分带性、风化壳油藏(晚期风化壳中)和内幕油藏(早期风化壳中)纵向叠置和复式油气聚集成藏模式等 3 个方面。文中对多期凝灰岩古风化壳的认识扩展了火山岩潜山的勘探深度,为火山岩潜山内幕油气勘探提供了理论依据。  相似文献   

X-射线检测图像识别的讨论   总被引：1，自引：1，他引：0  

曾祥照 《CT理论与应用研究》2004,13(1):29-31

概述了X-射线检测图像识别的影响因素;采取人工识别图像是可行和适宜的;人工、智能化识别图像是发展方向.介绍气瓶对接焊缝X射线实时成像检测.  相似文献   

南盘江盆地西南缘麻栗坡八布地区碎屑岩时代的厘定及其构造意义   总被引：1，自引：0，他引：1  

张斌辉  牛浩斌  卓皆文  李卿  张彬  陆生林 《地质学报》2019,93(9):2187-2196

南盘江盆地处于特提斯构造域和滨太平洋构造域的交汇部位。盆地西南缘的麻栗坡八布地区发育一套巨厚碎屑岩,因与八布蛇绿岩直接接触而意义重大,但目前还没有准确的同位素年代学依据,属性还存在争议。本文首次报道了碎屑岩上段中沉凝灰岩夹层的锆石LA- ICP- MS U- Pb年龄,结果为226±1Ma (n=17,MSWD=1.1)。结合古生物和接触关系,证实这套碎屑岩是中—上三叠统安尼阶到卡尼阶的板纳组—兰木组—平寨组。首次从上部层位厘定出一套滨岸- 潮坪相石英质细砾岩、石英砂岩、细砂岩沉积,发育平行层理、浪成交错层理、透镜状层理、干涉波痕等。从中三叠世的巨厚海相陆源碎屑浊流沉积到晚三叠世卡尼末期滨岸- 潮坪相沉积的演化,代表了南盘江前陆盆地中—晚三叠世的充填序列,卡尼阶平寨组与拉丁阶个旧组的平行不整合代表了印支运动第II幕。  相似文献   

黔西北及邻区安尼阶底界锆石U- Pb定年及对生物复苏的启示   总被引：1，自引：0，他引：1  

任光明  朱同兴  庞维华  王立全  金灿海  卢君勇  文俊  张鹏  周洋 《地质学报》2019,93(11):2770-2784

我国西南地区广泛分布着中-下三叠统海相(包括盆地相、斜坡相及台地相)沉积地层和多层凝灰岩。通过采用锆石LA-ICP-MS U-Pb测年方法,对黔西地区沙窝剖面和彝良柳溪剖面中/下三叠统界线上凝灰岩首次进行了锆石微区同位素定年,分别获得界线年龄为247.2±2.4Ma (2σ, MSWD=0.85)和247.4±1.4Ma (2σ,MSWD=0.51),界定了"黔中隆起"及北部坳陷区中/下三叠统界线时限,此年龄结果与国际地层年代表(2018版)建议的奥伦尼克阶/安尼阶(Olenekian-Anisian)界线年龄247.2Ma以及贵州关刀剖面Olenekian-Anisian界线附近凝灰岩锆石TIMS年龄247.2±0.1Ma高度吻合。凝灰岩岩石地球化学特征显示出富集K_2O、MgO,具明显负铕异常的特征,其物源可能来自古特提斯洋俯冲作用形成的大陆岩浆弧。幕式的火山活动可能是导致早-中三叠世生态环境间歇性恶化和生物迟滞复苏的重要原因,而深化对三叠纪幕式岩浆活动的认识,为我国西南地区三叠纪地层划分对比、构造演化以及探索三叠纪生物复苏-辐射与生态系统协同演化等提供依据。  相似文献   

大兴安岭北部拉布达林盆地中生代烃源岩的时代归属     

宗文明  张海华  孙雷  卞雄飞  张健  姚玉来 《地质与资源》2017,26(3):275-280

拉布达林盆地发育中生界厚层泥岩,具有烃源岩特征的岩层主要发育于原划归上库力组一段的中部和下部.拉布达林至下库力公路边491 km处发育原上库力组一段中部剖面,对产自该剖面厚层泥页岩下部的凝灰岩采用LA-ICP-MS技术,进行了锆石U-Pb年龄测定,获得的年龄值为156.7±1.8 Ma （MSWD=2.0）,指示其形成时代为晚侏罗世,将其划归满克头鄂博组.该研究结果不仅丰富了大兴安岭北部中生代年代地层学的年龄数据,同时为区域油气地质调查寻找火山岩覆盖区的烃源岩层提供基础资料.  相似文献   

Geochemistry and zircon U-Pb geochronology of the rhyolitic tuff on Port Island,Hong Kong: Implications for early Cretaceous tectonic setting     

Longlong Zhao  Lulin Wang  Mingzhong Tian  Fadong Wu 《地学前缘(英文版)》2017,8(3):565-581

Early Cretaceous rhyolitic tuffs, widely distributed on Port Island, provide insights into the volcanism and tectonic setting of Hong Kong. In this paper we present petrological, geochronological and geochemical data of the rhyolitic tuff to constrain the diagenesis age and petrogenesis of the rocks, tectonic setting and early Cretaceous volcanism of Hong Kong. The first geochronological data show that the zircons in the volcanic rocks have U-Pb age of 141.1–139.5 Ma, which reveals that the rhyolitic tuff on Port Island was formed in the early Cretaceous (K₁). Geochemically, these acid rocks, which are enriched in large ion lithophile elements (LILEs) and light rare earth elements (LREEs), and depleted in high field strength elements (HFSEs), belong to the high K calc-alkaline to shoshonite series with strongly-peraluminous characteristic. The geochemical analyses suggest that the volcanic rocks were derived from deep melting in the continental crust caused by basaltic magma underplating. Based on the geochemical analysis and previous studies, we concluded that the rhyolitic tuffs on Port Island were formed in a back-arc extension setting in response to the subduction of the Paleo-Pacific Plate beneath the Eurasian Plate.  相似文献   

Evolution of crystal sizes in the series of dissolution and precipitation events in open magma systems     

A.G. Simakin  I.N. Bindeman 《Journal of Volcanology and Geothermal Research》2008

We propose a model that describes the evolution of crystal sizes and crystal size distributions (CSD) of igneous phenocrysts in a sequence of dissolution and crystallization events. This model is based on the assumption that crystal dissolution is rate-limited by diffusion in melt while crystal growth is controlled by the slower kinetic of new nucleation and growth. As a result, the dissolution rate is inversely proportional to crystal size coming into effect through the curvature of the crystal's surface, but the growth rate does not depend on the crystal size. Closed-form analytical solution of equation for CSD is obtained. We apply results of modeling to quartz and zircon, two prime minerals in silicic igneous systems that are widely used in geochemical and isotopic investigations. The time-series of multiple solution–reprecipitation episodes generate concave-downward CSDs and this result fits well with experimental and natural observations on the abundant concave-down CSD in silicic igneous rocks. We suggest that maturation of crystal populations with sizes above several micrometers can not be caused by a size effect on the solubility of the crystals (Ostwald ripening), but is rather driven by thermal oscillations in experiments and in nature. The model predicts that mean crystal size increases with time proportionally to ∼ t^0.20, which is very close to the published experimental results for quartz maturation with the exponent of 0.19–0.22. Our proposed model gives an opportunity to use natural CSDs for interpretation of pre-eruptive magma history, when solubilities and diffusion data are available for constituent elements of the dissolving mineral. In particular, we present time estimates for maturing zircon populations in large volume ignimbrites and estimate that it takes 100–1000 yrs to mature an initially exponential CSD to a lognormal CSD.  相似文献