大气水在碎屑岩次生孔隙形成中的作用——以鄂尔多斯盆地三叠系延长组为例   总被引：49，自引：1，他引：48  

黄思静  武文慧刘洁沈立成  黄成刚 《地球科学》2003,28(4):419-424

鄂尔多斯盆地三叠系延长组砂岩储层分布于印支期不整合面之下, 次生孔隙是最主要的石油储集空间.在大量薄片研究及资料统计的基础上, 从岩石物性、长石溶蚀形成的次生孔隙、高岭石和长石含量纵向变化等证据出发, 认为延长组砂岩储层次生孔隙的形成机制与印支期暴露时间间隔中大气水的溶解作用有关, 而不是埋藏成岩过程中有机酸溶解作用的结果, 同时人们也应对鄂尔多斯盆地延长组碎屑岩储层质量预测模式作必要更改.   相似文献   

安徽巢湖平顶山下三叠统牙形石生物地层序列   总被引：6，自引：2，他引：4  

赵来时童金南  左景勋 《地球科学》2003,28(4):414-418

简要介绍安徽巢湖平顶山下三叠统牙形石生物地层研究的最新成果.对平顶山西坡剖面112.8 m厚的下三叠统地层所采集的286件牙形石样品, 经处理后获得2 870余枚牙形石样本, 经鉴定共有11属51种.这些属分别是Hindeodus, Isarcicella(?), Neogondolella, Neospathodus, Platyvillosus, Cratognathodus, Parachirognathus, Pachycladina, Ellisonia, Aduncodina和Cornudina.牙形石生物地层从老到新可划分为9个牙形石带: (1)Hindeodus typicalis- Neogondolella planata带; (2)Neogondolella krystyni带; (3)Neospathodus kummeli带; (4)Neospathodus dieneri带; (5)Neospathodus n. sp. C- Neospathodus n.sp. D带; (6) Neospathodus waageni带; (7)Neospathodus n.sp. M带; (8)Neospathodus eotriangularis带; (9) Neospathodus abruptus- Neospathodus homeri带.牙形石的组合面貌基本可与国内外其他地区牙形石带相对比.但其中牙形石(2), (3), (5), (7), (8)带为巢湖地区首次建立.在下三叠统菊石带控制下所建立的连续的牙形石分带对全球的三叠系阶的对比具有十分重要的意义. 关键词: 牙形石; 牙形石生物地层; 下三叠统; 安徽巢湖.   相似文献   

贵州早,中三叠世台地—盆地相过渡区层序地层及沉积地球化学特征   总被引：5，自引：0，他引：5  

杨瑞东 《高校地质学报》1998,4(1):95-102

在详细的露头层序地层学研究的基础上,建立了贵州早、中三叠世台地和盆地过渡区２个三级层序７个四级层序和层序地层格架。并分析了该地区早、中三叠世地层微量元素分布的规律,探讨了三叠纪层序地层与微量元素之间的关系。  相似文献   

The subduction of the Paleo‐Pacific Plate to the Jiamusi Block: Evidence from the Early Mesozoic sedimentary rocks of the eastern Jiamusi Block     

Zhongjie Xu  Jintao Kong  Rihui Cheng  Jianbo Zhou 《Island Arc》2020,29(1)

In order to provide references of the subduction process of the Paleo‐Pacific Plate beneath the Jiamusi Block, this paper studied the clastic rocks of the Nanshuangyashan Formation using modal analysis of sandstones, mudstone elements geochemistry, and detrital zircon U–Pb dating. These results suggest the maximum depositional age of the Nanshuangyashan Formation was between the Norian and Rhaetian (206.8 ±4.6 Ma, mean standard weighted deviation (MSWD) = 0.17). Whole‐rock geochemistry of mudstone indicates that source rocks of the Nanshuangyashan Formation were primarily felsic igneous rocks and quartzose sedimentary rocks, which were mainly derived from the stable continental block and a magmatic arc. Detrital zircon analysis showed the Nanshuangyashan Formation samples recorded four main age groups: 229–204 Ma, 284–254 Ma, 524–489 Ma and 930–885 Ma, and the provenances were attributed to the Jiamusi Block and a Late Triassic magmatic arc near the study area. Furthermore, the eastern Jiamusi Block was a backarc basin, affected by the subduction of the Paleo‐Pacific Plate in the Late Triassic, but the magmatic arc related to the subduction near the study area finally died out due to tectonic changes and stratigraphic erosion.  相似文献   

西秦岭西成和凤太矿集区三叠纪多金属成矿作用特征、规律及找矿方向     

王义天  毛景文  胡乔青  魏然  陈绍聪 《地球科学与环境学报》2021,(3):409-435

近十几年来,在西秦岭地区陆续开展的找矿勘查、成矿研究和同位素年龄精测等工作,取得了许多找矿新发现和成矿理论新认识,尤其是获得了一批精细的成岩成矿年龄数据,逐渐揭开了区内三叠纪多金属成矿作用的面纱,显示出三叠纪成矿作用的普遍性和多样性,并指示了巨大的成矿潜力.在西秦岭东段的西成和凤太矿集区中,三叠纪发育的矿种主要包括铅锌...  相似文献   

The synrift phase of the early Domeyko Basin (Triassic,northern Chile): Sedimentary,volcanic, and tectonic interplay in the evolution of an ancient subduction‐related rift basin     

Mauricio Espinoza  Diego Montecino  Vernica Oliveros  Natalia Astudillo  Paulina Vsquez  Robinson Reyes  Christopher Celis  Rodrigo Gonzlez  Juan Contreras  Christian Creixell  Amancay Martínez 《Basin Research》2019,31(1):4-32

The geodynamic setting along the SW Gondwana margin during its early breakup (Triassic) remains poorly understood. Recent models calling for an uninterrupted subduction since Late Palaeozoic only slightly consider the geotectonic significance of coeval basins. The Domeyko Basin initiated as a rift basin during the Triassic being filled by sedimentary and volcanic deposits. Stratigraphic, sedimentological, and geochronological analyses are presented in order to determine the tectonostratigraphic evolution of this basin and to propose a tectonic model suitable for other SW Gondwana‐margin rift basins. The Domeyko Basin recorded two synrift stages. The Synrift I (~240–225 Ma) initiated the Sierra Exploradora sub‐basin, whereas the Synrift II (~217–200 Ma) reactivated this sub‐basin and originated small depocentres grouped in the Sierra de Varas sub‐basin. During the rift evolution, the sedimentary systems developed were largely controlled by the interplay between tectonics and volcanism through the accommodation/sediment supply ratio (A/S). High‐volcaniclastic depocentres record a net dominance of the syn‐eruptive period lacking rift‐climax sequences, whereas low‐volcaniclastic depocentres of the Sierra de Varas sub‐basin developed a complete rift cycle during the Synrift II stage. The architecture of the Domeyko Basin suggests a transtensional kinematic where N‐S master faults interacted with ~NW‐SE basement structures producing highly asymmetric releasing bends. We suggest that the early Domeyko Basin was a continental subduction‐related rift basin likely developed under an oblique convergence in a back‐arc setting. Subduction would have acted as a primary driving mechanism for the extension along the Gondwanan margin, unlike inland rift basins. Slab‐induced dynamic can strongly influence the tectonostratigraphic evolution of subduction‐related rift basins through controls in the localization and style of magmatism and faulting, settling the interplay between tectonics, volcanism, and sedimentation during the rifting.  相似文献   

大兴安岭敖包查干地区安山岩年代学、地球化学研究   总被引：3，自引：0，他引：3  

程银行  杨俊泉  刘永顺  滕学建  李艳锋  彭丽娜  李影  刘洋 《华北地质》2012,35(2):118-127

在大兴安岭敖包查干地区首次识别出中三叠世安山质岩石,主要岩性为玄武质安山岩、粗面安山岩,应用锆石U—DbLA—ICPM—AS法定年,结果表明安山岩形成于234．8±3．2Ma～231．4±1．2Ma,属中三叠世。地球化学特征显示,研究区安山岩具高SiO2（54．19％～62．30％）、A12O3（15．78％～17．30％）、K20（1．77％～3．92％）、Na2O（2．95％～5．66％）、Na2O＋K20（5．4～8．99）的特征和低MgO（1．23％～3．66％,Mg^#=27．89～50．48）含量,并与SiO2含量呈负相关关系。岩石富Na20（Na2O／K2O=1．01～2．86）,铝指数A／CNK=0．81～1．21,属准铝质一弱过铝质钙碱性系列岩石。富集大离子亲石元素（LILE）K、Rb、Th和轻稀土元素,亏损高场强元素（HFSE）№、Ta、P、Ti,轻重稀土元素分馏明显[（LaMb）N=3．31～10．33]．无Eu异常（δEu=0．80～1．03）,显示弧火山岩的特征,但所研究样品的Zr、Hf呈弱正异常、Rb弱负异常却不同于正常岛弧安山岩,Zr／Y—Zr图解以及高钾特征显示出板内伸展构造环境的特征。综合研究表明敖包查干地区中三叠世钙碱性安山岩可能为古亚洲洋残余俯冲洋壳部分熔融的产物,与底侵作用有关,形成于大陆内部伸展构造环境。  相似文献   

Zircon U–Pb ages,geochemistry, and Sr–Nd–Pb isotopic compositions of Middle Triassic granodiorites from the Kaimuqi area,East Kunlun,Northwest China: implications for slab breakoff     

《International Geology Review》2012,54(2):257-270

The Qimantage area of Northwest China lies in the western part of the East Kunlun Orogenic Belt, and is dominated by late Permian to Late Triassic granitoids. Among these, the Middle Triassic granitoids are mainly distributed south of the North Kunlun Fault, and consist of two main granitic assemblages: the Kaimuqi assemblage in the east and the Mositu assemblage in the west. To better constrain the Indosinian tectonic evolution of this area, we present data on the geochronology, geochemistry, and petrology of ore-bearing granodiorites from the Kaimuqi area in eastern Qimantage. The granodiorite samples have porphyritic or fine-grained textures. Laser ablation inductively coupled plasma mass spectrometry U–Pb zircon dating yields emplacement ages of 238–242 Ma, interpreted here as the result of the Middle Triassic magmatism. The granodiorites are mostly of the high-K calc-alkaline series, and are enriched in light rare earth elements, depleted in heavy rare earth elements such as Nb, Ta, P, and Ti, and have weak negative Eu (Eu/Eu*) anomalies. The Kaimuqi granodiorites have lower SiO₂ and Sr contents, and higher Na₂O/K₂O ratios than the Mositu granodiorites. They also show initial ⁸⁷Sr/⁸⁶Sr ratios of 0.712151–0.715436, εNd(t) values of ?7.4 to ?6.3, and two-stage Nd model ages of 1.53–1.61 Ga. Together with their radiogenic Pb isotopic ratios for ²⁰⁶Pb/²⁰⁴Pb_(t) (18.271–18.622), ²⁰⁷Pb/²⁰⁴Pb_(t) (15.637–15.651), and ²⁰⁸Pb/²⁰⁴Pb_(t) (38.452–37.870), these data indicate both mantle and crustal contributions to the source of the granodiorites. Field investigations show that Middle Triassic granitoids in both the Mositu and Kaimuqi assemblages contain large numbers of mafic microgranular enclaves, which supports an interpretation of mantle and crustal magmatic mixing. Based on a comparison of these results with data from coeval granites in the Mositu assemblage, we propose that the Middle Triassic granitoids in the Qimantage area were produced at ca. 240 Ma, as a result of the end of subduction and the initiation of collision during the Variscan–Indosinian orogeny. Magma mixing may be interpreted as the result of slab breakoff in a subduction zone environment, which led to fluid metasomatism and induced partial melting of an enriched lithospheric mantle, resulting in the formation of voluminous granitic magma.  相似文献   

Late Triassic thickening of the Songpan–Ganzi Triassic flysch at the edge of the northeastern Tibetan Plateau     

《International Geology Review》2012,54(16):2008-2015

Growing geologic evidence documents incremental Mesozoic and early Cenozoic shortening and thickening of the Tibetan crust prior to the onset of the main Cenozoic orogenic event. The Tibetan crust shows spatial and temporal variability in thickness, style, and timing of thickening, and in plateau-forming processes. The Songpan–Ganzi area of northeastern Tibet provides evidence for shortening and thickening of the crust in Late Triassic time. An oil exploratory well (HC-1) of 7012.4 m located in the area shows at least six tectonic repetitions, resulting in more than ～46% thickening of the Triassic sequence. It indicates that the true thickness of the Songpan–Ganzi Triassic flysch is not 10–15 km as previously assumed, but not more than 3–5 km. Based on this evidence, combined with prior tectonostratigraphic studies, we propose that substantial crustal shortening and thickening, leading to initial plateau formation in the northeastern Tibetan Plateau, had already occurred during the Late Triassic.  相似文献   

Geochronology and geochemistry of Late Triassic bimodal igneous rocks at the eastern margin of the Songnen–Zhangguangcai Range Massif,Northeast China: petrogenesis and tectonic implications     

《International Geology Review》2012,54(2):196-215

Abstract

New zircon laser ablation inductively coupled plasma mass spectrometry and secondary ion mass spectroscopy U–Pb ages, and Hf isotope and whole-rock geochemical data are reported for Mesozoic igneous rocks from the eastern margin of the Songnen–Zhangguangcai Range Massif, Northeast China, in order to document the petrogenesis of the igneous rocks and reconstruct the early Mesozoic tectonic setting of the region. Zircons from five representative igneous rocks are euhedral–subhedral and display oscillatory growth zoning or striped absorption in cathodoluminescence images, suggesting a magmatic origin. The dating results indicate that granite, gabbro, and rhyolite from the eastern Songnen–Zhangguangcai Range Massif formed during Late Triassic (204–211 Ma). The Late Triassic granitoids and rhyolites have an affinity to A-type granites or rhyolites. Their zircon ε_Hf(t) values and Hf two-stage model ages range from –3.8 to +3.8 and from 999 to 1485 Ma, respectively, indicating that their primary melts were derived from the partial melting of the Meso-Proterozoic crust. The geochemistry of coeval gabbros, which reflects primary magma composition, shows a significant large ion lithophile element (e.g. Ba and Sr) enrichment and high field strength element (i.e. Zr, Hf, Nb, Ta, and Ti) depletion. Based on zircon ε_Hf(t) values (–4.2 to +2.8) and Hf single-stage model ages (746–1031 Ma), we conclude that the mafic magma is the product of partial melting of lithospheric mantle that was metasomatically enriched by fluids derived from the subducted oceanic crust. The Late Triassic magmatism along the eastern margin of the Eurasian continent has bimodal magma compositions, indicating an extensional setting after the final closure of the Palaeo-Asian Ocean rather than being related to subduction of the Palaeo-Pacific Plate beneath the Eurasian continent. The occurrence of Late Triassic igneous rocks on the eastern side of the Mudanjiang Fault suggests that this fault does not represent the suture zone between the Songnen–Zhangguangcai Range and Jiamusi massifs.  相似文献