甘肃省景泰正路下志留统复理石杂砂岩沉积地球化学特征

位于北祁连造山带东段甘肃省景泰正路一带的下志留统肮脏沟组为一套巨厚的浊流相陆源碎屑岩,以杂砂岩为主,夹有板岩,属典型的浊流沉积。薄片的镜下观察结果表明,其粒度为0.05~4.00 mm,岩性为细粒-中、粗粒砂岩、含砾砂岩。对5块采集于复理石中的杂砂岩样品进行岩性组合判定和主要元素地球化学分析结果表明,w(SiO2)为61.83%~69.90%,w(K2O)/w(Na2O)为0.89~1.46。利用数据对比及w(K2O)/w(Na2O)—w(SiO2)等判别图的分析结果对其物源区的性质及沉积大地构造背景进行分析和判别的研究结果表明,北祁连造山带东段甘肃省景泰正路一带下志留统肮脏沟组的陆源碎屑主要来源于活动大陆边缘岩浆岛弧源区和造山带源区,反映了卷入造山带的岛弧、活动大陆边缘的弧后盆地的物源背景。沉积地球化学特征揭示的沉积大地构造背景为弧后前陆盆地背景,与碰撞后的大地构造背景相吻合。     

Detrital Zircon Dating of Meso- and Neoproterozoic Rocks in North China and Its Implications

New dates from Meso- and Neoproterozoic strata contribute to the recently defined Precambrian stratigraphical timescale of China agreed by the Subcommission on the Precambrian System, and the National Commission on Stratigraphy of China on Nov. 24, 2009. First, the age range of the Changcheng System, including the Changzhougou, Chuanlinggou, Tuanshanzi and Dahongyu formations has been constrained to 1.8–1.6 Ga. Second, the Jixian System including the Gaoyuzhuang, Yangzhuang, Wumishan, Hongshuizhuang and Tieling formations has been constrained to 1.6–1.4 Ga. Third, an as-yet unnamed (undefined) system (1.4–1.0 Ga) is only developed in the Xiamaling Formation at the Jixian section, Tianjing. Fourth, the Qingbaikou System, including the Luotuoling and Jing’eryu formations has been constrained to 1.0–0.78 Ga. Fifth, the Nanhuan System ranges between 780–635 Ma, and the Sinian System is within 635–542 Ma. However, according to a series of SHRIMP U-Pb dates from the late Precambrian in the Jiangnan Orogen Belt in South China Platform, the constrained strata will be redefined as in the upper part of the Qingbaikou System. To aid global geodynamics, it is useful to denote a late Precambrian section with unified, precise and high-precision chronological dating; this is here defined in North China Block and Jiaoliao-Korean Block. However, the Neoproterozoic Qingbaikou study in North China will be influence in whole Meso- and Neoproterozoic in the Jiangnan Orogenic Belt in between the Yangtze Block and the Cathaysia Block in South China.     

NEW EVIDENCES FOR LATE QUATERNARY ACTIVITY IN THE SOUTHERN SEGMENT OF THE YISHU-TANGTOU FAULT,THE TAN-LU FAULT ZONE,AND ITS TECTONIC IMPLICATION

The Tan-Lu Fault Zone(TLFZ), a well-known lithosphere fault zone in eastern China, is a boundary tectonic belt of the secondary block within the North China plate, and its seismic risk has always been a focus problem. Previous studies were primarily conducted on the eastern graben faults of the Yishu segment where there are historical earthquake records, but the faults in western graben have seldom been involved. So, there has been no agreement about the activity of the western graben fault from the previous studies. This paper focuses on the activity of the two buried faults in the western graben along the southern segment of Yishu through combination of shallow seismic reflection profile and composite drilling section exploration. Shallow seismic reflection profile reveals that the Tangwu-Gegou Fault(F₄)only affects the top surface of Suqian Formation, therefore, the fault may be an early Quaternary fault. The Yishui-Tangtou Fault(F₃)has displaced the upper Pleistocene series in the shallow seismic reflection profile, suggesting that the fault may be a late Pleistocene active fault. Drilling was implemented in Caiji Town and Lingcheng Town along the Yishui-Tangtou Fault(F₃)respectively, and the result shows that the latest activity time of Yishui-Tangtou Fault(F₃)is between(91.2±4.4)ka and(97.0±4.8)ka, therefore, the fault belongs to late Pleistocene active fault. Combined with the latest research on the activity of other faults along TLFZ, both faults in eastern and western graben were active during the late Pleistocene in the southern segment of the Yishu fault zone, however, only the fault in eastern graben was active in the Holocene. This phenomenon is the tectonic response to the subduction of the Pacific and Philippine Sea Plate and collision between India and Asian Plate. The two late Quaternary active faults in the Yishu segment of TLFZ are deep faults and present different forms on the surface and in near surface according to studies of deep seismic reflection profile, seismic wave function and seismic relocation. Considering the tectonic structure of the southern segment of Yishu fault zone, the relationship between deep and shallow structures, and the impact of 1668 Tancheng earthquake(M=8(1/2)), the seismogenic ability of moderate-strong earthquake along the Yishui-Tangtou Fault(F₃)can't be ignored.     

伟晶岩型锂矿成矿构造背景研究

锂是银白色的、自然界最轻的金属,广泛应用于纺织、陶瓷、冶金、核能、新能源等领域,有“高能金属”、“21世纪的能源金属”之称。锂矿床按成因类型可分为内生和外生两种类型,内生型可具体分为花岗伟晶岩型、花岗岩型、云英岩型和岩浆热液型,外生型则包括盐湖型及地下卤水型（赵一鸣等,2004）。伟晶岩型锂矿主要开采锂辉石、透锂云母、锂云母、磷铝锂石等,是锂矿资源的重要来源。     

大兴安岭南段不同构造环境中的两类花岗岩

大兴安岭南段主要分布有海西和燕山两个时代的花岗岩类,它们在产出构造环境、地貌形态、地质产状、岩石组合、侵位方式、造岩矿物、岩石化学、锶同位素初始比值及其矿产等诸方面,都存在着较大的差别。海西期花岗岩类主要与板块俯冲有关,属挤压环境下形成的造山钙碱性花岗岩系列。燕山期花岗岩类则主要与大陆边缘断裂活动有关,属引张环境下地幔上隆所引发的亚碱性—碱性非造山花岗岩系列,且随时间推移,拉张强度加剧,岩石碱性程度增高。     

雅安地区青衣江流域第四纪阶地特征分析

雅安青衣江流域阶地非常发育。通过砾石的岩性、粒度、扁平面的统计,研究区阶地砾石主要来源于青衣江上游地区,在万古场古青衣江流向由北东改为向东,在阳坪现代青衣江流向一致为东南,流速有逐渐减小的趋势。根据阶地测年和阶面相对高程分析,从早更新世至全新世本区至少有7次构造抬升,万古场阶地最大抬升幅度达85 m,最大抬升速率为0.532 mm/a,阳坪阶地抬升幅度最大达到52 m,最大抬升速率为1.25 mm/a。     

Numerical simulations of protostellar encounters — II. Coplanar disc–disc encounters

It is expected that an average protostar will undergo at least one impulsive interaction with a neighbouring protostar whilst a large fraction of its mass is still in a massive, extended disc. Such interactions must have a significant impact upon the evolution of the protostars and their discs.   We have carried out a series of simulations of coplanar encounters between two stars, each possessing a massive circumstellar disc, using an SPH code that models gravitational, hydrodynamic and viscous forces. We find that during a coplanar encounter, disc material is swept up into a shock layer between the two interacting stars, and the layer then fragments to produce new protostellar condensations. The truncated remains of the discs may subsequently fragment; and the outer regions of the discs may be thrown off to form circumbinary disc-like structures around the stars. Thus coplanar disc–disc encounters lead efficiently to the formation of multiple star systems and small- N clusters, including substellar objects.     

新疆普鲁一带下古生界地层岩石组合及构造环境

西昆仑地块是西昆仑造山带的重要组成部分，南北边界分别为康西瓦—苏巴什华力西期缝合带和库地—其曼于特加里东期缝合带。新疆普鲁一带下古生界地层，分布于西昆仑地块东部，主要由一套海相火山岩和浅海陆棚相细碎屑岩组成，并遭受了绿片岩相的变质作用。通过1：25万《于田一伯力克幅)区调工作，将新疆普鲁一带下古生界地层厘定为下古生界奥陶—志留系，认为形成的大地构造环境为大陆活动边缘。     

秭归龙会观5.1级震区及其邻区新生代以来的地壳应力场特征

为了研究三峡坝库区的地壳稳定性,根据奥陶－侏罗纪地层中构造变形的实际观测资料,计算了秭归龙会观５．１级震区及其邻区新生代以来区域应力场的主应力方向。结果表明：主压应力为北东东向,主张应力为北北西向;现代构造应力场与新生代以来应力场基本一致;晚第三纪以来,该区构造应力场相对稳定和统一。