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1.
藏南仲巴地区早白垩世日朗组出露于特提斯喜马拉雅北亚带,整体为黄绿色火山岩屑砂岩,局部层位可见页岩与泥岩,分析为一套深海海底扇沉积组合。本文仔细分析了日朗组砂岩岩石学特征及鲍马序列和槽模沉积构造等沉积学特征,结果表明:日朗组砂岩成分成熟度和结构成熟度均不高,具有近源物源的特点;槽模构造古水流数据统计表明古流向由南向北,指示物质组分来源于南侧特提斯喜马拉雅和/或印度克拉通。砂岩碎屑组分统计结果表明日朗组的物源区构造背景属于克拉通内部及石英再旋回区。碎屑锆石U-Pb年龄频谱图对比进一步表明其物源区为印度稳定大陆边缘,外加一套早白垩世火山碎屑物质的输入。仲巴地区日朗组物源特征反映了印度大陆北缘早白垩世由深部断裂引起的一次强烈的火山事件,可能与印度大陆从澳大利亚-南极大陆裂解有关。 相似文献
2.
西藏南部桑单林地区出露一套晚白垩世-始新世深水沉积的地层,下部为晚白垩世以石英砂岩和粉砂质页岩为主的桑单林组,上部为始新世含长石岩屑砂岩、硅质岩和硅质页岩的者雅组,由于断层错断,二者之间的古新世地层缺失.砂岩的岩石学分析表明,桑单林组石英砂岩的成分成熟度和结构成熟度均较高,杂基含量少,为硅质胶结;者雅组长石岩屑砂岩中,不稳定组分明显增加,杂基含量高,主要为泥质胶结.运用重矿物组合以及全岩主量元素、微量元素和稀土元素组成对砂岩的物源区分析表明,桑单林组砂岩形成于稳定的被动大陆边缘,碎屑物质来源于印度克拉通内部,而者雅组砂岩中存在明显的火成岩物质的输入,这些火山物质只可能来自于沉积盆地北部.桑单林组和者雅组砂岩的物源区的明显变化,反映了古新世末期-早始新世的一次碰撞事件:印度大陆与亚洲大陆的碰撞或者印度大陆与洋内岛弧的碰撞. 相似文献
3.
特提斯喜马拉雅南亚带作为印度被动大陆北缘的主要构造单元,相较于其他类似构造单元发育着多套特殊的石英砂岩,意味着被动大陆边缘物源区陆源碎屑供应能力的多次变化,而引起印度被动大陆北缘石英砂岩沉积的构造背景和构造意义尚不明确。以特提斯喜马拉雅南亚带的岗巴地区古新统基堵拉组石英砂岩为例,通过砂岩碎屑成分分析、古流向恢复、重矿物分析和碎屑锆石年代学方法,对基堵拉组石英砂岩的沉积学及物源区特征,以及蕴含的成因和构造意义进行探讨。从沉积相分析结果来看,在早古新世岗巴地区所属的板块为印度被动大陆边缘,处于新特提斯洋的海岸线附近,以滨岸相为主,显示了一种浅海陆棚到陆相的变化。从砂岩岩相学的结果分析,基堵拉组的陆源碎屑物主要是成熟度极高的石英砂岩,同时古水流近NNE方向。从碎屑锆石年代学数据分析结果可知,基堵拉组的碎屑锆石年龄特征与早白垩世德干高原地区相吻合。故认为基堵拉组石英砂岩的形成是由于印度北缘的陆源碎屑供应量突然增多与被动大陆边缘物源区构造抬升导致,而引起被动大陆边缘物源区构造抬升的原因主要与德干大火成岩省形成相关。最终认为石英砂岩的发育成因与印度大陆北缘德干大火成岩省形成时构造隆升所导致的稳定克拉通再活化有关。 相似文献
4.
徽成盆地是西秦岭造山带内一个具有代表性的盆地,保留较完整的地层记录.早白垩世田家坝组、周家湾组和鸡山组为一套砂砾岩沉积组合序列.本文通过对早白垩世砂岩的古水流恢复、砾石成分与含量、重矿物和地球化学分析,对沉积岩物源区特征和原型盆地进行探讨.古水流恢复和砾石成分统计表明,沉积物主要是近源堆积,主要来自于盆地南缘和北部.重矿物研究结果表明,早白垩世砂岩母岩以岩浆岩为主,并有少量变质岩/沉积岩.地球化学分析表明,早白垩世砂岩为成熟度较低的硬砂岩和长石/岩屑砂屑岩.稀土元素标准化配分曲线呈现轻稀土富集、重稀土平坦和弱Eu负异常特征.砂岩物源区组成判别图研究表明,早白垩世砂岩的物源区主要出露长英质火山岩.砂岩源区构造环境判别图解及特征指数分析表明,早白垩世砂岩源区主要形成于大陆岛弧和活动大陆边缘.结合区域资料和前人研究,表明早白垩世徽成地区发育走滑拉分盆地. 相似文献
5.
虎林盆地北部坳陷中、新生代碎屑岩源区构造背景与物源区分析 总被引：1，自引：0，他引：1
虎林盆地北部坳陷地层包括下白垩统裴德组、下云山组、上云山组、珠山组，渐新统虎林组和中新统富锦组。北部坳陷砂岩-泥岩由常量、微量和稀土元素组成，揭示早白垩世砂岩-泥岩源区构造背景为活动大陆边缘，渐新统斗新统砂岩-泥岩多呈现出从活动大陆边缘向大陆岛弧转换的地球化学特征。结合沉积相特征和岩屑所反映的源区岩性特点，认为早白垩世时期物源主要来自于坳陷北部完达山造山带和南部古隆起；渐新统物源则主要来自盆地东北部的完达山造山带，并且碎屑岩的原始物质均来自上地壳。 相似文献
6.
肖斌 《矿物岩石地球化学通报》2014,(4)
砂岩地球化学特征可以有效反映物源区地质信息。为了探讨查干凹陷下白垩统巴音戈壁组-苏红图组砂岩物源属性与源区构造环境,进行了砂岩显微薄片鉴定和主量元素测定,结果显示,巴音戈壁组砂岩与苏红图组砂岩的岩石学特征较相似,主量元素特征稍有差异。综合研究表明,砂岩成熟度低,杂基含量较高,岩性以岩屑长石砂岩和长石岩屑砂岩为主;物源区母岩主要为中酸性岩类(长英质为主),其次为中性和酸性岩类,也有极少量基性岩成分;研究区总体上长期处于构造活跃地区,气候寒冷干燥,碎屑物质化学风化程度低,源区构造环境以活动大陆边缘和岛弧环境为主,也有少量物源来自被动大陆边缘,基本上没有来自反映稳定构造环境的克拉通内部的物源;主体物源区构造环境以活动大陆边缘为主,其构造环境性质长期保持相对稳定。 相似文献
7.
藏南珠峰地区下白垩统发现海底扇沉积 总被引：7，自引：2，他引：5
西藏南部珠穆朗玛峰地区在构造古地理上属印度板块的北部,中—新生代期间位于新特提斯洋东段的南侧,构成冈瓦纳大陆的北部边缘。下白垩统在聂拉木古错一带出露最好,在岗巴东山一带次之,是目前研究珠峰地区早白垩世地层和沉积的两个重要地点。古错一带下白垩统厚2400余米,划分为古错一组至古错五组5个岩石地层单位。沉积以黑灰色粉砂质页岩、黑色页岩为主,夹有多层厚层—块状暗黄绿色长石岩屑砂岩,以及少量钙质细砂岩和含岩屑粒泥灰岩。产菊石、少量双壳和遗迹化石,时代从晚侏罗世Tithonian末期至早白垩世Albian期。过去认为这里的下白垩统… 相似文献
8.
通过详实的野外调查和室内研究,在西藏吉瓦地区新发现了砂岩型铜矿床,赋矿层位为渐新统日贡拉组,矿床类型为层控矿床。为探讨日贡拉组砂岩的物源特征及其构造背景、查明其含矿物质来源,通过碎屑矿物定量分析、元素地球化学方法及重矿物组合分析等一系列物源分析方法对日贡拉组的物质来源进行了研究。结果显示,研究区主要岩性为岩屑砂岩,岩屑主要成分为酸性火山岩,砂岩结构成熟度低,分选磨圆差。碎屑组分分析表明物源集中在火山弧物源区,地球化学特征为硅质含量高、LREE富集、HREE相对亏损、显示Eu负异常,均表明物源与酸性火山岩密切相关;日贡拉组砂岩的大地构造背景主要为大陆岛弧,砂岩碎屑来自上地壳长英质源区。重矿物组合以反映物源为中酸性岩浆岩成分的赤褐铁矿+磁铁矿、锆石、电气石、石榴子石为主,沉积环境为气候干旱、水体较浅的富氧环境。锆石形态特征指示物源距母岩区较近,重矿物的相关性分析也指示了物源与火山岩密切相关。研究区的日贡拉组砂岩与早白垩酸性火山岩微量元素及重矿物的对比表明,碎屑物质源区特点从岩石学特征、地球化学特征及重矿物组合特征上均表现出了亲缘关系,物源成分与火山作用紧密相关,很可能主要来自班公湖-怒江洋壳南向俯冲与雅鲁藏布江洋壳北向俯冲双重制约条件下产生于火山弧环境中的早白垩世火山岩。日贡拉组发现了砂岩型铜矿,火山岩提供了成矿物质来源,为寻找同类型的矿床开启思路。 相似文献
9.
沉积物的地球化学成分在沉积岩物源分析及构造背景的研究中具有重要的作用.对研究区4口钻孔中的姚家组砂岩进行了详细的岩石学和地球化学研究,结果显示,砂岩碎屑颗粒石英含量最高,长石次之,岩屑含量最低,平均值分别为42%、37%和21%,具有锆石+钛磁铁矿+石榴子石的重矿物组合,反映源岩以酸性岩浆岩或变质岩为主,Dickinson判别图解表明物源主要来自于大陆物源区;姚家组砂岩的稀土元素以轻稀土富集、重稀土平坦、中度铕负异常为特征.砂岩CIA值为52.02~60.16,平均值为56.69,反映了干燥气候背景下弱的化学风化作用.源岩属性判别图解表明源岩为再旋回的古老沉积物及长英质火山岩.主量、微量和稀土元素的构造背景判别图解综合表明姚家组砂岩物源区为被动大陆边缘构造环境,结合区域构造演化,认为姚家组砂岩的物源为华北克拉通北缘燕山陆内造山带发育的火山-沉积岩系. 相似文献
10.
合肥盆地中生界沉积物物源分析及构造意义 总被引：1，自引：0，他引：1
应用砂岩端元组分、重矿物成分变化等方法对合肥盆地及其南缘的中生界沉积物物源研究表明:合肥盆地大致以六安断裂为界分为南带和北带,其物源有显著差异.北带沉积物主要来源于华北板块,特别是早、中侏罗世,从晚侏罗世到早白垩世,大别造山带大规模的剥露开始,其母岩物质已经完全参与了盆地主体区的沉积;南带中、晚侏罗世沉积的物源来自北淮阳带,但大别造山带也有相当程度的贡献,凤凰台组沉积时期是大别造山带隆升最快、幅度最大的时期.早白垩世盆地的充填物质主要来自大别高压变质岩带,指示其俯冲、折返已经到达地表并持续遭受剥蚀,自中晚侏罗世到早白垩世早期剥蚀程度逐渐加大.从源区看,北带侏罗系样品的源区更接近于被动大陆边缘,南带多为主动大陆边缘.而白垩系样品无论北带还是南带多落入或靠近主动大陆边缘,说明早白垩世滨太平洋构造域已经占主导作用,南北差异减弱,早白垩世早期是南北向区域挤压特提斯构造域向北东向伸展的滨太平洋构造域转换的关键时期.此外值得注意的是中生界少数样品反映了岛弧区背景,许多样品具有混合源区的明显特征. 相似文献
11.
藏南古近纪甲查拉组物源分析及其对印度-欧亚大陆碰撞启动时间的约束 总被引：5，自引：1，他引：5
位于特提斯喜马拉雅北亚带的江孜地区古近纪甲查拉组角度不整合于晚白垩世宗卓组之上,系该地区最高(时代最晚)海相地层。运用岩石学和地球化学方法对其进行分析研究结果表明该组物源区主要为近源再旋回造山带,岩屑的母岩类型主要是岩浆弧成因的中性、中酸性安山质火山岩。新生代以前,特提斯喜马拉雅属于印度板块的被动大陆边缘,从特提斯喜马拉雅南亚带向北亚带显示了一种从浅水陆棚到深水盆地的变化,在侏罗-白垩纪时其陆源碎屑物主要是成熟度极高的石英砂岩,所以甲查拉组的碎屑物质只能来源于当时的冈底斯弧地区,所获有限的古水流证据也指示了这一点。从欧亚大陆侵蚀下来的碎屑物质被带到原印度大陆地区沉积,暗示该区的特提斯洋壳已经完全消失,印度与欧亚大陆在特提斯喜马拉雅中、东部产生了初始的陆-陆碰撞,其碰撞的启动时间为甲查拉组开始沉积的65 M a±。 相似文献
12.
新疆库鲁克塔格南华系砂岩碎屑组成对其物源及盆地演化的指示 总被引：1，自引：0，他引：1
库鲁克塔格南华系记录了塔里木北缘同期的火山-沉积事件和蚀源区物质组成及演化的信息。该区不同剖面内南华系各组砂岩碎屑组分的统计分析显示,贝义西组砂岩在不同剖面内组成差异显著:西山口剖面以岩屑砂岩为主,且岩屑为火山岩岩屑与沉积岩岩屑,物源为再旋回地层,而依格孜塔格剖面以长石砂岩和岩屑长石砂岩为主,岩屑主要为变质岩岩屑,物源为下伏古元古代高级变质岩。砂岩碎屑组成在剖面上垂向的变化表明贝义西组沉积期与照壁山组沉积期间（725 Ma±）存在一个沉积转型事件,导致贝义西组之上的照壁山组、阿勒通沟组及特瑞艾肯组砂岩组成在不同区域趋于一致,转变为代表基底隆起-过渡大陆区物源的典型“长石砂岩”。南华系砂岩碎屑组成与大陆裂谷盆地沉积砂岩相似,且物源区存在由前裂谷地层-过渡裂谷肩部-切割裂谷肩部-克拉通内部的连续演化过程,是库满凹陷早期裂解的岩相学记录。 相似文献
13.
LUCA CARACCIOLO SALVATORE CRITELLI FABRIZIO INNOCENTI NIKO KOLIOS PIERO MANETTI 《Sedimentology》2011,58(7):1988-2011
New sandstone petrology and petrostratigraphy provide insights on Palaeogene (Middle Eocene to Oligocene) clastics of the Thrace Basin in Greece, which developed synchronously with post‐Cretaceous collision and subsequent Tertiary extension. Sandstone petrofacies are used as a tool to unravel complex geodynamic changes that occurred at the southern continental margin of the European plate, identifying detrital signals of the accretionary processes of the Rhodope orogen, as well as subsequent partitioning related to extension of the Rhodope area, followed by Oligocene to present Aegean extension and wide magmatic activity starting during the Early Oligocene. Sandstone detrital modes include three distinctive petrofacies: quartzolithic, quartzofeldspathic and feldspatholithic. Major contributions are from metamorphic basement units, represented mostly by low to medium‐grade lithic fragments for the quartzolithic petrofacies and high‐grade metamorphic rock fragments for the quartzofeldspathic petrofacies. Volcaniclastic sandstones were derived from different volcanic areas, with a composition varying from dominantly silicic to subordinate intermediate products (mainly rhyolitic glass, spherulites and felsitic lithics). Evolution of detrital modes documents contributions from three key source areas corresponding to the two main crystalline tectonic units: (i) the Variegated Complex (ultramafic complex), in the initial stage of accretion (quartzolithic petrofacies); (ii) the Gneiss–Migmatite Complex (quartzofeldspathic petrofacies); and (iii) the Circum‐Rhodope Belt. The volcaniclastic petrofacies is interbedded with quartzofeldspathic petrofacies, reflecting superposition of active volcanic activity on regional erosion. The three key petrofacies reflect complex provenance from different tectonic settings, from collisional orogenic terranes to local basement uplift and volcanic activity. The composition and stratigraphic relations of sandstones derived from erosion of the Rhodope orogenic belt and superposed magmatism after the extensional phase in northern Greece provide constraints for palaeogeographic and palaeotectonic models of the Eocene to Oligocene western portions of the Thrace Basin. Clastic detritus in the following sedimentary assemblages was derived mainly from provenance terranes of the Palaeozoic section within the strongly deformed Rhodope Massif of northern Greece and south‐east Bulgaria, from the epimetamorphic units of the Circum‐Rhodope Belt and from superposed Late Eocene to Early Oligocene magmatism related to orogenic collapse of the Rhodope orogen. The sedimentary provenance of the Rhodope Palaeogene sandstones documents the changing nature of this orogenic belt through time, and may contribute to a general understanding of similar geodynamic settings. 相似文献
14.
With the aim of constraining the influence of the surrounding plates on the Late Paleozoic–Mesozoic paleogeographic and tectonic evolution of the southern North China Craton (NCC), we undertook new U–Pb and Hf isotope data for detrital zircons obtained from ten samples of upper Paleozoic to Mesozoic sediments in the Luoyang Basin and Dengfeng area. Samples of upper Paleozoic to Mesozoic strata were obtained from the Taiyuan, Xiashihezi, Shangshihezi, Shiqianfeng, Ermaying, Shangyoufangzhuang, Upper Jurassic unnamed, and Lower Cretaceous unnamed formations (from oldest to youngest). On the basis of the youngest zircon ages, combined with the age-diagnostic fossils, and volcanic interlayer, we propose that the Taiyuan Formation (youngest zircon age of 439 Ma) formed during the Late Carboniferous and Early Permian, the Xiashihezi Formation (276 Ma) during the Early Permian, the Shangshihezi (376 Ma) and Shiqianfeng (279 Ma) formations during the Middle–Late Permian, the Ermaying Group (232 Ma) and Shangyoufangzhuang Formation (230 and 210 Ma) during the Late Triassic, the Jurassic unnamed formation (154 Ma) during the Late Jurassic, and the Cretaceous unnamed formation (158 Ma) during the Early Cretaceous. These results, together with previously published data, indicate that: (1) Upper Carboniferous–Lower Permian sandstones were sourced from the Northern Qinling Orogen (NQO); (2) Lower Permian sandstones were formed mainly from material derived from the Yinshan–Yanshan Orogenic Belt (YYOB) on the northern margin of the NCC with only minor material from the NQO; (3) Middle–Upper Permian sandstones were derived primarily from the NQO, with only a small contribution from the YYOB; (4) Upper Triassic sandstones were sourced mainly from the YYOB and contain only minor amounts of material from the NQO; (5) Upper Jurassic sandstones were derived from material sourced from the NQO; and (6) Lower Cretaceous conglomerate was formed mainly from recycled earlier detritus.The provenance shift in the Upper Carboniferous–Mesozoic sediments within the study area indicates that the YYOB was strongly uplifted twice, first in relation to subduction of the Paleo-Asian Ocean Plate beneath the northern margin of the NCC during the Early Permian, and subsequently in relation to collision between the southern Mongolian Plate and the northern margin of the NCC during the Late Triassic. The three episodes of tectonic uplift of the NQO were probably related to collision between the North and South Qinling terranes, northward subduction of the Mianlue Ocean Plate, and collision between the Yangtze Craton and the southern margin of the NCC during the Late Carboniferous–Early Permian, Middle–Late Permian, and Late Jurassic, respectively. The southern margin of the central NCC was rapidly uplifted and eroded during the Early Cretaceous. 相似文献
15.
《Journal of Asian Earth Sciences》2011,42(6):494-503
Detrital zircon U–Pb data from sedimentary rocks in the Hengyang and Mayang basins, SE China reveal a change in basin provenance during or after Early Cretaceous. The results imply a provenance of the sediment from the North China Craton and Dabie Orogen for the Upper Triassic to Middle Jurassic sandstones and from the Indosinian granitic plutons in the South China Craton for the Lower Cretaceous sandstones. The 90–120 Ma age group in the Upper Cretaceous sandstones in the Hengyang Basin is correlated with Cretaceous volcanism along the southeastern margin of South China, suggesting a coastal mountain belt have existed during the Late Cretaceous. The sediment provenance of the basins and topographic evolution revealed by the geochronological data in this study are consistent with a Mesozoic tectonic setting from Early Mesozoic intra-continental compression through late Mesozoic Pacific Plate subduction in SE China. 相似文献
16.
Despite abundant data on volcaniclastic sand(stone), the compositional, spatial and temporal distribution of volcanic detritus within the sedimentary record is poorly documented. One of the most intricate tasks in optical analysis of sand(stone) containing volcanic particles is to distinguish grains derived by erosion of ancient volcanic rocks (i.e. palaeovolcanic, noncoeval grains) from grains generated by active volcanism (subaqueous and/or subaerial) during sedimentation (neovolcanic, coeval grains). Deep-marine volcaniclastic sandstones of the Middle Topanga Group of southern California are interstratified with 3000-m-thick volcanic deposits (both subaqueous and subaerial lava and pyroclastic rocks, ranging from basalt, andesite to dacite). These rocks overlie quartzofeldspathic sandstones (petrofacies 1) of the Lower Topanga Group, derived from deep erosion of a Mesozoic magmatic arc. Changes in sandstone composition in the Middle Topanga Group provide an example of the influence of coeval volcanism on deep-marine sedimentation. Volcaniclastic strata were deposited in deep-marine portions of a turbidite complex (volcaniclastic apron) built onto a succession of intrabasinal lava flows and on the steep flanks of subaerially emplaced lava flows and pyroclastic rocks. The Middle Topanga Group sandstones are vertically organized into four distinctive petrofacies (2–5). Directly overlying basalt and basaltic-andesite lava flows, petrofacies 2 is a pure volcanolithic sandstone, including vitric, microlitic and lathwork volcanic grains, and neovolcanic crystals (plagioclase, pyroxene and olivine). The abundance of quenched glass (palagonite) fragments suggests a subaqueous neovolcanic provenance, whereas sandstones including andesite and minor basalt grains suggest subaerial neovolcanic provenance. This petrofacies probably was deposited during syneruptive Periods, testifying to provenance from both intrabasinal and extrabasinal volcanic events. Deposited during intereruptive periods, impure volcanolithic petrofacies 3 includes both neovolcanic (85%) and older detritus derived from plutonic, metamorphic and palaeovolcanic rocks. During post-eruptive periods, the overlying quartzofeldspathic petrofacies 4 and 5 testify to progressive decrease of neovolcanic detritus (48–14%) and increase of plutonic-metamorphic and palaeovolcanic detritus. The Upper Topanga Group (Calabasas Formation), conformably overlying the Middle unit, has dominantly plutoniclastic sandstone (petrofacies 6). Neovolcanic detritus is drastically reduced (4%) whereas palaeovolcanic detritus is similar to percentages of the Lower Topanga Group (petrofacies 1). In general, the volcaniclastic contribution represents a well-defined marker in the sedimentary record. Detailed compositional study of volcaniclastic strata and volcanic particles (including both compositional and textural attributes) provides important constraints on deciphering spatial (extrabasinal vs. intrabasinal) and temporal relationships between neovolcanic events (pre-, syn-, inter- and post-eruptive periods) and older detritus. 相似文献