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排序方式: 共有38条查询结果,搜索用时 15 毫秒
1.
贵州晴隆中二叠统大厂层砾岩成因研究   总被引:1,自引:0,他引:1  
贵州晴隆中二叠统大厂层中—上部产出一套呈囊状、透镜状分布的砾岩层。对大厂层砾岩沉积序列、结构、构造特征和矿物组合进行研究,结果表明:沉积序列为"反粒序",砾岩成分单一,基本为玄武质,是由峨眉山玄武岩直接改造而成,未发育河道相沉积特征;大厂层砾石具特殊的"泥化边"构造,是玄武岩在海水中大量水解的直接证据,填隙物中的青磐岩化矿物组合表明砾岩遭受了低温热液的改造。填隙物具有接近凝灰岩的Zr/Hf(30.7~43.4,均值38.0),揭示玄武岩在改造形成砾石的过程中有火山碎屑(火山灰)参与成岩;砾石和填隙物相对玄武岩贫Na(Na2O)富K(K2O),三者具有相似的稀土配分模式,其中∑REE呈规律性变化(玄武岩最高,砾石次之,填隙物中最低)。沉积背景分析认为,峨眉地幔柱作用使地壳发生了差异抬升,抬升一侧暴露遭受剥蚀形成不整合面,相对沉降一侧继续接受沉积,大厂层正是峨眉山玄武岩前锋带在局限海盆边缘(沉降侧),于茅口灰岩之上继续沉积的产物。大厂层砾岩形成机制是:炽热玄武岩流在海水中急剧爆裂,同时火山碎屑参与沉积,形成的玄武岩前积层(淬碎熔岩角砾)及凝灰岩,沉积在茅口组灰岩之上;在后期的演化过程中,炽热玄武岩冷凝收缩,柱状节理发育,在潮汐流和沿岸流的相互作用下不断磨蚀形成大厂层砾岩。  相似文献   
2.
刘宝成  袁力 《吉林地质》1994,13(2):75-81
中心取样钻探是一种全新的钻探方法,具有效率快、取样准确、岩样采取率高的特点。可用于砾岩型金矿勘探评价,获取的矿层深度、品位、厚度、岩心采取率等均能满足地质要求,利用回返物质能够进行正常地质编录。  相似文献   
3.
茅山山脉东麓的砾岩层位和时代   总被引:1,自引:1,他引:0  
通过对茅山东麓砾岩层的实地研究,以5条剖面的岩性、产状和生物等特征为依据,将砾岩分为三类,并分别论述其层位时代。提出了与前人不同的观点。  相似文献   
4.
黄建松  郭玮  杨萍  易纲 《古地理学报》2019,21(4):557-576
唐王陵砾岩自20世纪60年代发现以来,其形成时代和沉积环境就争议不断,至今没有定论。作者根据唐王陵附近多个露头点唐王陵砾岩与上下地层的接触关系、岩性和古生物特征,结合渭北隆起西段2口油气探井的钻探结果,将其地质时代确定为晚奥陶世赫南特期;基于北秦岭岛弧在中奥陶世之后持续隆升,秦岭北坡及其以北的古生代和更老地层不断向北倾覆倒转,同时遭受不同程度的变质与剥蚀,北秦岭和华北陆块之间的弧后盆地演变为前陆盆地并逐渐闭合的共识,并结合该套砾岩地层的反旋回沉积特征和发育大量碎屑流、颗粒流及浊流等重力流沉积的事实,认为唐王陵砾岩是一套沉积在晚奥陶世末期,不断抬升并遭受剧烈崩塌剥蚀的北秦岭以北的前陆盆地陡岸背景下的前陆斜坡脚海底扇沉积体。该结论不但厘清了唐王陵砾岩与东庄页岩的时代归属,也为北秦岭和渭北地区加里东期前陆盆地的构造演化及石油地质研究奠定了基础。  相似文献   
5.
Lenses of radioactive Quartz Pebble Conglomerates (QPC) and associated quartzites are exposed along western margin of Archean Bonai Granite in Singhbhum-Orissa Craton, eastern India intermittently spreading over a strike length of 8–10 km. QPCs are radioactive while quartzites are mostly non-radioactive in nature. The purpose of the research is to investigate and characterize the radioactive QPC and quartzites geochemically to decipher their paleo-weathering conditions, provenance characteristics and possible tectonic setting of deposition. Geochemical data suggest moderate to high chemical weathering conditions in the provenance areas of QPC and quartzites. Major, trace and REE data indicate predominantly felsic to partly mafic-ultramafic sources for the deposition of radioactive Quartz Pebble Conglomerates from the surrounding Archean terrain.Elevated values of Th, U, Pb, La, Ce, Y and low Sc with high critical trace elemental ratios of Th/Sc, La/Sc, Th/Cr and Zr/Sc in radioactive QPC indicate their derivation from felsic igneous source. Low concentration of Th and Sc in quartzites compared to QPC and their variable Th/Sc ratios indicate both felsic and mafic sources for quartzites, albeit their preferential felsic affiliation. Higher Cr/Th ratios in quartzites (18.4), moderate Cr/Th in QPC (5.42), low to moderate Y/Ni in QPC (0.36–12.4) and quartzite (0.29–1.88), along with Au ranging from 30 to 1527 ppb, Pt up to 188 ppb and 682 ppb in QPC and quartzites respectively point towards some contribution from mafic-ultramafic source as well. REE patterns and in particular negative Eu anomalies for both QPC and quartzites further support their derivation from felsic rocks and could possibly linked to some of the phases of Archean Singhbhum Granite and Bonai Granite. Granitic to pegmatitic source for QPC is also revealed by the presence of rounded to sub-rounded monazite, zircon and thorian-uraninite grains in their matrix. Study indicates that QPC and quartzites were deposited in a passive margin tectonic setting developed during Archean between a span of 3.3 and 3.16 Ga along the western margin of Bonai Granite when the reducing condition was prevalent as indicated by their low Th/U ratios (<4.0) and presence of detrital grains of uraninite and pyrite in QPC. Radioactive QPC from western margin of Archean Singhbhum-Orissa Craton bears broad resemblance with QPC from Witwatersrand basin of South Africa and Elliot Lake, Canada and thus appears to be ideal sites for exploring QPC hosted U (+Au-PGE) mineralization in the analogous areas.  相似文献   
6.
晚侏罗世承德盆地砾岩碎屑源区分析及构造意义   总被引:5,自引:0,他引:5  
河北承德及寿王坟盆地在晚侏罗世土城子期堆积了大量的粗碎屑沉积。砾石成分统计结果显示,承德-寿王坟盆地充填的土城子组碎屑母岩组合主要有三种,其中火山岩、花岗质岩石和变质岩组合在承德盆地占绝时优势,反映了当时盆地以北的"内蒙地轴"为主要的蚀源区。向北逆冲的双庙断裂将承德盆地分成南北两个部分,断裂两侧的砾石成分组合基本相同,显示出碎屑物质共同来源于北部,同时也暗示了该断裂在土城子期可能没有强烈的活动(强烈活动期可能在土城子组之后?)。分析表明,承德盆地南部的不对称向斜构造两侧砾石成分截然不同,说明该向斜构造控制了碎屑分布,是同沉积期形成的。该盆地南侧的碎屑供应量远远小于北侧,反映了控制盆地南缘发育的向北逆冲的灰窑断层可能是一条次要的同沉积断裂。在晚侏罗世整体向南推进的逆冲断裂系统中,灰窑断裂和双庙断裂应属于背向逆冲断层。承德盆地中大量的粗碎屑堆积与同期冲断带的耦合关系分析,指示了这一时期盆地北侧存在强烈的逆冲断裂活动。作为主要物源区,北部的"内蒙地轴"在晚侏罗世发生了强烈的隆升-剥蚀作用,推测当时在地貌上可能存在近E—W走向的古山系(或古高原?)。  相似文献   
7.
闽西南“丁屋岭砾岩”孢子的发现   总被引:1,自引:1,他引:1  
闽西南丁屋岭一带浅变质岩系中夹持着一套紫红色粗碎屑岩系 ,1970年《长汀幅》区域地质调查时将其划为震旦系南沱组下段 ,之后改称丁屋岭组下段 (习称“丁屋岭砾岩”) ,认为是澄江运动或晋宁运动的产物。长期以来因缺少化石 ,对其地层划分和时代归属一直存在争议。本次《瑞金市幅》区调工作首次在“丁屋岭砾岩”中获得孢子 ,为将“丁屋岭砾岩”置于上泥盆统提供了有力证据  相似文献   
8.
A new study of the geology of the Nahr-el-Kelb region, situated 10 km northeast of Beirut, shows a complex tectonics not seen by Dubertret [Carte géologique au 1/200?000e feuille de Beyrouth avec notice explicative, 1954] while establishing his geologic section. The Neogene series observed (conglomerate, succession of sandstone, marl, clayey limestone, limestone, covered by massive limestone), lie disconformably on Cretaceous series and occur with a vertical dip in the Ghosta flexure in contradiction with the old vision of Dubertret [Carte géologique au 1/200?000e feuille de Beyrouth avec notice explicative, 1954; La bordure orientale de la Méditerranée en tant que témoin de l'évolution des accidents de l'Est africain, in: XXe Congrès géologique international, Associacion Servicios Geologicos Africanos Mexico, 1956, pp. 377–384] on the Neogene tectonics in Lebanon. In this flexure, close to the road crossing to Jiita, the upper conglomerate beds have variable dips. Starting close to the vertical, as for the underlying Cretaceous series, the dip gradually decreases in the upper conglomerate beds, to become horizontal at the top of the formation. The upper conglomerate is thus post-Miocene in age. To cite this article: R.M. Hamzeh, T. Haj-Chahine, C. R. Geoscience 337 (2005).  相似文献   
9.
10.
Coarse clastic rocks in the Liuqu Conglomerate, formed in both terrestrial and subaqueous settings, record a Paleogene phase in the tectonic evolution of Tibet. Facies changes are commonly abrupt with rapid changes in clast types, grain size and stratal patterns. Sediments were derived from the leading (northern) edge of the Indian margin and a Late Jurassic–Cretaceous intraoceanic island arc that lay within Tethys. The coarse clastic sedimentary rocks of the Liuqu conglomerates are extremely proximal, but are locally offset relative to their original source terranes. They record aspects of the history of collision between these terranes and are interpreted to have been deposited in oblique–slip basins that developed along the zone of collision. The absence of clasts derived from terranes to the north of the Yarlung–Tsangpo suture suggests that basins associated with deposition of the Liuqu Conglomerate developed prior to the final collision between India and Asia.  相似文献   
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