Tectonic nature of the NE Asian continental margin during the Late Jurassic–Early Cretaceous: constraints from the geochronology and geochemistry of igneous rocks in the NE North China Craton     

Xiao-Ming Zhang  Chen-Yang Sun  Feng Wang  Yu Li 《International Geology Review》2020,62(15):1949-1970

ABSTRACT

This paper presents geochronological, geochemical, and zircon Hf–O isotope data for late Mesozoic intrusive rocks from the northeastern North China Craton (NCC), with the aim of constraining the late Mesozoic tectonic nature of the NE Asian continental margin. U–Pb zircon data indicate that the Late Mesozoic magmatism in the northeastern NCC can be subdivided into two stages: Late Jurassic (161 ? 156 Ma) and Early Cretaceous (125 ? 120 Ma). Late Jurassic magmatism consists mainly of monzogranites. These monzogranites display high Sr/Y ratios and the tetrad effect in their REE, respectively, and have negative ε_Hf(t) values (?22.6 to ?15.8). The former indicates that the primary magma was generated by partial melting of thickened NCC lower crust, the latter suggests that the monzogranites were crystallized from highly fractionated magma, with the primary magma derived from partial melting of lower continental crust. Combined with the spatial distribution and rock associations of the Late Jurassic granitoids, we conclude that the Late Jurassic magmatism in the eastern NCC formed in a compressional environment related to oblique subduction of the Paleo-Pacific Plate beneath the Eurasia. The Early Cretaceous magmatism consists mainly of granitoids and quartz diorites. The quartz diorites formed by mixing of melts derived from the mantle and lower crust. The coeval granitoids are classified as high-K calc-alkaline and metaluminous to weakly peraluminous series. Some of the granitoids are similar to A-type granites. The granitoid ε_Hf(t) values and T_DM2 range from ?14.3 to ?1.4 and 2089 to 1274 Ma, respectively. These values indicate that their primary magma was derived from partial melting of lower crustal material of the NCC, but with a contribution of mantle-derived material. We therefore conclude that Early Cretaceous magmatism in the northeastern NCC occurred in an extensional environment related to westward subduction of the Paleo-Pacific Plate beneath Eurasia.  相似文献   

LATE QUATERNARY ACTIVITY OF THE SOUTHEASTERN SECTION OF ZHONGDIAN-DAJU FAULT          下载免费PDF全文

LI Guang-tao  SU Gang  CHENG Li  LI Feng  WU Hao 《地震地质》2019,41(3):545-560

The southeast section of Zhongdian-Daju Fault is located in the northern part of Haba and Yulong Snow Mountain, belonging to the southwestern boundary of the secondary block in northwestern Sichuan, an important boundary fault striking 310°~320° on the whole. The nature of the fault, the age of its activity and the slip rate are of great significance for the analysis of the secondary block movement in the northwestern Sichuan and the intersection relationship with the eastern piedmont fault of Yulong Mountains. Based on the 1 ︰ 5 million-scale active fault geological mapping, this paper studies in detail the stratigraphic landform, scarp landform, surface rupture, typical fault profile and river terrace along the fault. Based on the research results, we divide the southeastern section of Zhongdian-Daju Fault into two sub-segments, the Majiacun-Daju sub-segment and the Daju-Dadong sub-segment, according to the geometric structure, fault landforms and fault activity. (1)Fault scarp:In the Majiacun-Daju sub-segment, the fault parallelly controls the two sides of the Haba fault depression. It cuts the late Pleistocene moraine deposits, forming a fault scarp of about 4.5km long and(14±2)m high. The continuity of the scarp is very good, and it is also very obvious in the remote sensing image. In the Daju-Dadong sub-segment, a scarp with a height of about 2m is formed, and an optical luminescence dating sample is collected from the upper part of the gravel layer on the second-order terrace to obtain an age of(22±2.2)ka. (2)Horizontal dislocation:In the Majiacun-Daju sub-segment, through the analysis of the development of outwash fans in the area and the measurement and induction of the gully dislocations, it is considered that there are at least three stages of outwash fans developed in the area and there may be four phases of faulting. That is, the earliest-stage outwash fan and gully are horizontally dislocated about 1km; the second-stage outwash fan and gully are horizontally dislocated about 47m, and the vertical dislocation is about(14±2)m; the gully in the third stage outwash fan is horizontally dislocated twice, the first dislocation formed a beheaded gully with a dislocation of 22m, and the second formed a beheaded gully with a dislocation of 8.5m. It is further proved that the fault has strong activity since the Holocene in the Majiacun to Daju area. In the Daju-Dadong sub-segment, there are no obvious horizontal dislocations in the alluvial deposits since the Holocene. Only 3~4 gullies are found to be offset right-laterally in the ridges east of Wenhe Village, with the maximum dislocation of 210m, which may be the older phase dislocation. (3)Surface rupture:In the northwest direction of Dabazi Village on the T3 terrace in the basin between Majiacun and Daju, an earthquake surface rupture zone is found, extending in the NW direction. The rupture zone left clear traces on the about 1m-thick, hard T₃ terrace surface formed by calcification of sand gravels, and the overburden either upwarps and bulges, or ruptures, generates ground fissures, or forms small pull-apart "depressions" locally. However, the rupture zone is not large in size, about 350m long, 60m wide at the widest point, and 0.3~1.5m high. It is partially en-echelon or obliquely arranged, dominated by compressive ruptures. Through observation, the possibility of artificial transformation is ruled out for these upwarping bulges, ruptures or ground fissures. The fault section is found in the southeast direction of the rupture zone. The slickensides at the section show that the fault is dominated by right-lateral strike-slip with a small amount of thrust. In the eastern sub-segment, only intermittently distributed surface ruptures are found in the northern part of the village, and the scale is small. In summary, through the field geological survey, it is found that the Majiacun-Daju sub-segment is a Holocene active segment. Though the Daju-Dadong sub-segment also offset the late Pleistocene to Holocene strata, it is considered that its Holocene activity is weak in terms of either the dislocation amount or the slip rate of this segment. By analyzing the geological and geomorphological evidences, such as fault scarps, horizontal dislocation and surface ruptures along the fault, it is considered that the Majiacun-Daju sub-segment is a right-lateral strike-slip fault with a normal faulting component, and its vertical slip rate since the late Pleistocene is(0.4~0.8)mm/a, the horizontal slip rate is 1.5~2.4mm/a. The Daju-Dadong sub-segment is dominated by right-lateral strike-slip with a normal faulting component, and its vertical slip rate since the late Late Cenozoic is 0.1mm/a. The formation of the NW-trending surface rupture zone found in the Daju Basin is very young, where there are only two major earthquakes, namely, the M_S6.4 1966 Zhongdian earthquake and the 1996 Lijiang M_S7.0 earthquake, and both earthquakes produced NW-oriented surface rupture zones. Therefore, it cannot be ruled out that the rupture zone is a product of the 1966 Zhongdian M_S6.4 earthquake or the 1996 Lijiang M_S7.0 earthquake.  相似文献   

科学与主权：晚清民国时期西方学者在中国的地质学考察     

孙承晟 《地质论评》2021,67(5):67060015-67060015

晚清随着中国国门洞开,西方学者、传教士、商人、探险家以“科学无国界”的旗号,将中国视为一个巨大的“露天博物馆”,纷纷来华进行各种科学考察。其中比较著名的如庞佩利、李希霍芬、塞切尼、奥勃鲁切夫、维理士、安得思以及斯文·赫定等,在中国先后组织了多次系统的考察,在地质学等领域取得了许多影响深远的成果。这些考察不仅丰富了西方地质学家对中国地质的认识,对之后的中国学者也颇多裨益。民国以后,西人的考察活动激起了中国学者的民族主义反弹,不断遭遇中国学者的主权诉求,尤其是斯文·赫定组织的西北考察成为其中的一个标志性事件。在民间团体的努力下,政府对外国人在中国的考察活动逐渐作出了明确的法律限制,中国学者亦自发开展独立的地质学考察和研究。  相似文献   

鄂尔多斯盆地及周缘地区上二叠统沉积特征          下载免费PDF全文

张道锋  李程善  刘文香  马国伟  李文厚  卢子兴 《古地理学报》2021,23(1)

基于野外地质露头观察、岩心描述、薄片鉴定和地球化学等分析测试资料的综合分析,对鄂尔多斯盆地及周缘地区上二叠统石千峰组沉积岩石类型、沉积构造、沉积相类型及沉积体系空间展布等方面开展研究。结果表明,石千峰组主要发育冲积平原、三角洲平原、三角洲前缘、浅湖和南部海陆过渡的潟湖、沙坝等沉积环境,石千峰期,古气候干燥炎热,沉积古地形相对平缓,物源供给充足,形成了一套紫红色、棕红色泥岩和浅灰色中粗粒长石岩屑砂岩、岩屑长石砂岩、长石砂岩为主的地层。盆地北部三角洲规模大,以辫状河道发育沉积特征为主,砂体厚度大、横向分布稳定,而盆地南部三角洲规模相对较小。石千峰期,海水可能多次入侵盆地南部麟游-韩城-乡宁一带,发育海相夹层和沙坝沉积,一定程度上影响了南部的沉积环境和砂体展布。  相似文献   

滇西漕涧地区崇山杂岩带始新世花岗岩的发现及其地质意义     

黄亮  浦涛  刘军平  王晓林  刘小春  熊波  宋冬虎 《地球学报》2021,42(5):579-592

崇山杂岩带为滇西三江造山系西侧边缘的一条重要边界构造,属青藏高原造山带的南东缘.带内岩浆活动强烈,前人认为其主要由晚元古代、中生代的花岗岩组成;而据地质调查发现,带内新生代的岩浆作用十分发育.本文对带内新发现的灰白色黑云二花岗岩进行研究,获得了锆石U-Pb LA-ICP-MS年龄为34.88 Ma和35.25 Ma,表明其侵位于古近纪始新世.岩石地球化学表明,黑云二花岗岩为钾玄质-高钾钙碱性系列的过铝质花岗岩类,稀土元素配分曲线为右倾,其中LREE明显富集,HREE为不同程度亏损,具明显的负Eu异常;富集Rb、Th、Ce、Sm和亏损K、Ba、Ta、Hf、Y等元素,且为淡色花岗岩特征;据锆石Hf同位素测试分析,εHf(t)值为–2.35～+2.33和TDM2为962～1259 Ma,表明了花岗岩岩浆源区为壳幔混合的产物,以及源岩主要源自中元古代—新元古代陆壳基底物质的部分熔融.综合研究认为,始新世黑云二长花岗岩形成于喜马拉雅期碰撞造山向造山晚期转换阶段,是一套典型的"超厚地壳"部分熔融和壳幔相互作用的淡色花岗岩;以及其侵位时间代表了漕涧地区喜马拉雅碰撞造山阶段的完成和造山晚期阶段的开始,且转换时间约为35 Ma.  相似文献   

Seesaw Pattern of Rainfall Anomalies between the Tropical Western North Pacific and Central Southern China during Late Summer     

Xinyu LI  Riyu LU 《大气科学进展》2019,36(3):261-270

It is well known that suppressed convection in the tropical western North Pacific(WNP) induces an anticyclonic anomaly,and this anticyclonic anomaly results in more rainfall along the East Asian rain band through more water vapor transport during summer, as well as early and middle summer. However, the present results indicate that during late summer(from mid-August to the beginning of September), the anomalous anticyclone leads to more rainfall over central southern China(CSC), a region quite different from preceding periods. The uniqueness of late summer is found to be related to the dramatic change in climatological monsoon flows: southerlies over southern China during early and middle summer but easterlies during late summer. Therefore, the anomalous anticyclone, which shows a southerly anomaly over southern China, enhances monsoonal southerlies and induces more rainfall along the rain band during early and middle summer. During late summer,however, the anomalous anticyclone reflects a complicated change in monsoon flows: it changes the path, rather than the intensity, of monsoon flows. Specifically, during late summers of suppressed convection in the tropical WNP, southerlies dominate from the South China Sea to southern China, and during late summers of enhanced convection, northeasterlies dominate from the East China Sea to southern China, causing more and less rainfall in CSC, respectively.  相似文献   

清末耕地空间分布格局重建方法比较   总被引：4，自引：2，他引：2  

姜蓝齐  张丽娟  臧淑英  张学珍 《地理学报》2015,(4)

揭示历史时期土地利用/覆盖变化是认识人类活动对气候和环境影响的基础。本文在耕地面积、人口数量、土地利用及森林分布等多源数据基础上,分别以近代耕地空间分布格局和历史时期耕地潜在分布区为边界条件,通过构建耕地垦殖倾向指数模型分配耕地面积,在1 km×1 km象元尺度上重建了清末(1908年)松嫩平原耕地空间格局,并对重建结果进行分析比较。结果表明:1两种方法重建的耕地空间分布范围格局基本一致,耕地空间定位吻合率约为68%。清末(1908年)耕地集中分布在松嫩平原东部和南部地区;2以历史时期耕地潜在分布为边界条件的重建结果,较以近代耕地空间分布格局为限制范围的重建结果更准确,更符合历史事实。  相似文献   

Carbon and Oxygen Stable Isotope Values and Microfossils at 41.4–4.5 ka BP in Tai Co, Tibet, China, and Their Paleoclimatic Significance     

ZHENG Mianping  LIU Junying  MA Zhibang  WANG Hailei  MA Nina 《《地质学报》英文版》2011,85(5):1036-1056

Two sedimentary sections were measured at Tai Co (Co means lake in Tibetan) in western Tibet, China. The two sections are almost all composed of clay carbonate beds except in their lower parts where there are carbonized plants at >10 cm depths and dark-colored carbonate clay and clay at 50–70 cm depths, yielding abundant gastropods, ostracods, and charophytes. The carbon and oxygen stable isotope values of carbonate, ostracods, and charophytes and ecological features of microfossil communities indicate the following climatic change in the area from 41.4 to 4.5 ka BP: at 41.4–26.2 ka BP, the climate was relatively wet; at 26.2–25.5 ka BP, it was slightly warm-dry; at 25.5–22.5 ka BP, it was warm-wet; at 22.5–21.0 ka BP, it was slightly cold-wet; at 20.5–17.5 ka BP, it became cold abruptly and slightly wet, implying the climate of the last glacial maximum; at 17.5–16.0 ka BP, it was slightly cold-dry; at 16.0–11.8 ka BP, it was slightly warm-wet; at 11.8–10.4 ka BP, it was relatively cold-dry, roughly equivalent to the climate of the Younger Dryas, and at 10.4 ka BP, the temperatures began to rise again; at 10.4–9.4 ka BP, it was slightly warm-wet; at 9.4–8.5 ka BP, there occurred short warm-wet oscillations; at 8.5–7.9 ka BP, it was slightly dry-cold, representing a strong temperature-lowering and drying event in the postglacial stage; at 7.8–6.3 ka BP, it was slightly warm-wet; at 6.3–4.5 ka BP, the climate tended to be cold-dry. 4.5 ka BP recorded the maximum aridity since the late part of the late Pleistocene.  相似文献   

Changes of Late Mesozoic Tectonic Regimes around the Ordos Basin (North China) and their Geodynamic Implications   总被引：4，自引：0，他引：4  

ZHANG Yueqiao  SHI Wei  DONG Shuwen 《《地质学报》英文版》2011,85(6):1254-1276

A synthesis is given in this paper on late Mesozoic deformation pattern in the zones around the Ordos Basin based on lithostratigraphic and structural analyses. A relative chronology of the late Mesozoic tectonic stress evolution was established from the field analyses of fault kinematics and constrained by stratigraphic contact relationships. The results show alternation of tectonic compressional and extensional regimes. The Ordos Basin and its surroundings were in weak N-S to NNE-SSW extension during the Early to Middle Jurassic, which reactivated E-W-trending basement fractures. The tectonic regime changed to a multi-directional compressional one during the Late Jurassic, which resulted in crustal shortening deformation along the marginal zones of the Ordos Basin. Then it changed to an extensional one during the Early Cretaceous, which rifted the western, northwestern and southeastern margins of the Ordos Basin. A NW-SE compression occurred during the Late Cretaceous and caused the termination of sedimentation and uplift of the Ordos Basin. This phased evolution of the late Mesozoic tectonic stress regimes and associated deformation pattern around the Ordos Basin best records the changes in regional geodynamic settings in East Asia, from the Early to Middle Jurassic post-orogenic extension following the Triassic collision between the North and South China Blocks, to the Late Jurassic multi-directional compressions produced by synchronous convergence of the three plates (the Siberian Plate to the north, Paleo-Pacific Plate to the east and Lhasa Block to the west) towards the East Asian continent. Early Cretaceous extension might be the response to collapse and lithospheric thinning of the North China Craton.  相似文献   

刺参染色体制备的初步研究   总被引：2，自引：0，他引：2       下载免费PDF全文

谭杰  孙慧玲  高菲  杨爱国  燕敬平  于东祥  刘志鸿  周丽青 《海洋科学》2011,35(3):8-11

为探索取材容易、结果稳定可靠的刺参染色体制备方法,分别以刺参(Apostichopus japortfcus)胚胎和成体为材料对刺参染色体制片方法进行了研究.结果表明,以原肠后期胚胎为材料采用常规的热滴片法,细胞有丝分裂指数最高,获得分裂相效果最好;以成体呼吸树、成体肠组织为材料时,也能获得中期分裂相染色体,但存在着细...  相似文献