Caledonian Low-Temperature Granulite-Facies Metamorphism in the West Kunlun Orogenic Belt—SHRIMP Chronological Evidence from Zircon

The West Kunlun orogenic belt is located at the conjunction of the paleo-Asian tectonic system and the Tethys tectonic system. Petrological and mineralogical studies of the Early Cambrian metamorphic surface crust in this region have shown that in case the metamorphism reached low-temperature granulate facies, the typical mineral assemblage is biotite-garnet-silimanite-K feldspar-plagioclase-quartz. The peak metamorphic temperatures are within the range of 720–740°C and the pressure is 0.6 GPa ±. Three types of metamorphic zircon have been detected in the metamorphic rocks: the complex inclusion-bearing type ; the early relic zircon inclusion-bearing type; and the inclusion-free type. SHRIMP age determination of these three types of metamorphic zircon have revealed that these zircons were formed principally during 400–460 Ma, indicating that pre-Cambrian metamorphic surface crust rocks underwent low-temperature granulite facies metamorphism during the Caledonian. In combination with the geological characteristics of this region, it is considered that when the oceanic basin was closed, there occurred intense intracontinental subduction (type A), bringing part of the Early Cambrian metamorphic basement in this region downwards to the lower crust. Meanwhile, there were accompanied with tectonic deformation at deep levels and medium- to high-grade metamorphism. This study provided important chronological and mineralogical evidence for the exploration of the evolutionary mechanism and process of the West Kunlun Early Paleozoic. Part of the results from the research project “ Research on the West Kunlun pre-Cambrian tectonic events” under the program “ Research on the important geological problems of China’ s pre-Cambrian” (No. 200113900070) sponsored by the China National Geological Surveying Bureau.     

Palaeomagnetic results from the ca. 1130 Ma Borgmassivet intrusions in the Ahlmannryggen region of Dronning Maud Land, Antarctica, and tectonic implications

Detailed palaeomagnetic and rock magnetic analyses provide improved palaeomagnetic results from 23 sites in the Borgmassivet intrusions in the Ahlmannryggen region of Dronning Maud Land, East Antarctica. These intrusions are of similar age to their host, the ca. 1130 Ma Ritscherflya Supergroup (RSG). A mean direction of D=235.4°, I=−7.6° with k=45.9 and α₉₅=4.5° was obtained from this study. When combined with previously reported results from 11 sites in the same region, including sites from the Ritscherflya Supergroup, it gives an overall mean direction for 34 sites from the igneous suite with D=236.5°, I=−3.6°, k=27.9 and α₉₅=4.8°. Isothermal remanent magnetization (IRM) experiments on several specimens suggest magnetite or titanomagnetite as the primary remanence carrier, while high temperature magnetic susceptibility experiments indicate the presence of single domain particles. These observations, together with field evidence and the high coercivities and unblocking temperatures, support a primary origin for the observed characteristic remanence. The Borgmassivet palaeomagnetic pole lies at 54.5°E, 8.3°N with A₉₅=3.3°. If Antarctica is moved to its Gondwanan position adjacent to southeast Africa, the Borgmassivet pole (BM) coincides with that of the African well-established, well-dated (1100 Ma) Umkondo Large Igneous Province pole, supporting the hypothesis that the Grunehogna craton of Dronning Maud Land was part of the Kalahari craton of southern Africa at ca. 1100 Ma.     

From geometry to dynamics of microstructure: using boundary lengths to quantify boundary misorientations and anisotropy

The microstructure of a quartzite experimentally deformed and partially recrystallised at 900 °C, 1.2 GPa confining pressure and strain rate 10⁻⁶/s was investigated using orientation contrast and electron backscatter diffraction (EBSD). Boundaries between misoriented domains (grains or subgrains) were determined by image analysis of orientation contrast images. In each domain, EBSD measurements gave the complete quartz lattice orientation and enabled calculation of misorientation angles across every domain boundary. Results are analysed in terms of the boundary density, which for any range of misorientations is the boundary length for that range divided by image area. This allows a more direct comparison of misorientation statistics between different parts of a sample than does a treatment in terms of boundary number.The strain in the quartzite sample is heterogeneous. A 100×150 μm low-strain partially recrystallised subarea C was compared with a high-strain completely recrystallised subarea E. The density of high-angle (>10°) boundaries in E is roughly double that in C, reflecting the greater degree of recrystallisation. Low-angle boundaries in C and E are produced by subgrain rotation. In the low-angle range 0–10° boundary densities in both C and E show an exponential decrease with increasing misorientation. The densities scale with exp(−θ/λ) where λ is approximately 2° in C and 1° in E; in other words, E has a comparative dearth of boundaries in the 8–10° range. We explain this dearth in terms of mobile high-angle boundaries sweeping through and consuming low-angle boundaries as the latter increase misorientation through time. In E, the density of high-angle boundaries is larger than in C, so this sweeping would have been more efficient and could explain the relative paucity of 8–10° boundaries.The boundary density can be generalised to a directional property that gives the degree of anisotropy of the boundary network and its preferred orientation. Despite the imposed strain, the analysed samples show that boundaries are not, on average, strongly aligned. This is a function of the strong sinuosity of high-angle boundaries, caused by grain boundary migration. Low-angle boundaries might be expected, on average, to be aligned in relation to imposed strain but this is not found.Boundary densities and their generalisation in terms of directional properties provide objective measures of microstructure. In this study the patterns they show are interpreted in terms of combined subgrain rotation and migration recrystallisation, but it may be that other microstructural processes give distinctive patterns when analysed in this fashion.     

Confirmation of an Early Cretaceous age for the Qihulin Formation in eastern Heilongjiang Province, China: constraints from a new discovery of radiolarians

The coal-bearing, alternating marine and non-marine Longzhaogou Group in eastern Heilongjiang, northeastern China, has long been considered as Jurassic, or mainly Jurassic, in age. However, recent studies have demonstrated that the ammonites and dinoflagellate cysts are of Early Cretaceous age. This has now been confirmed by new radiolarian evidence. The radiolarian fauna recovered from the upper Qihulin Formation of the Longzhaogou Group consists of nine poorly preserved species referable to nine genera. Novixitus is a Cretaceous genus, and the specimens of Archaeodictyomitra sp. and Xitus sp. recovered resemble A. vulgaris Pessagno and X. spicularius (Aliev), respectively.     

新疆西达里亚T-II油藏储层三维建模研究

在新疆西达里亚T-Ⅱ油气藏的储层表征研究中,首先进行了地质及测井解释,在此基础上应用地质统计学方法进行了三维储层地质建模,建模过程中采用先建立砂层格架,再建立属性参数的“两步建模”研究思路,理论上减少了砂体与属性参数的解释矛盾与误差,提高了属性模型精确度.通过实际生产动态对属性模型进行检验,证明建模结果是正确的.     

Theoretical Study on Stochastic Modeling of Combined Gravity-Magnetic-Electric-Seismic Inversion and Its Application

As gravity field,magnetic field,electric field and seismic wave field are all physical fields,their object function,reverse function and compound function are certainly infinite contiuously differentiable func-tions which can be expanded into Taylor (Fourier) series within domain of definition and be further reduced in-to solving stochastic distribution function of series and statistic inference of optimal approximation,This is the basis of combined gravity-magnetic-electric-seismic inversion built on the basis of separation of field and source gravity-magnetic difference-value(D-value)trend surface,taking distribution-independent fault sys-tem as its unit,depths of seismic and electric interfaces of interests as its corresponding bivariate compound re-verse function of gravity-magnetic anomalies and using high order polynomial(high order trigonometric func-tion)approximating to its series distribution,The difference from current dominant inversion techniques is that,first,it does not respectively create gravity-seismic,magnetic-seismic deterministic inversion model from theoretical model,but combines gravity-magnetic-electric-seismic stochastic inversion model from stochastic model;second,after the concept of equivalent geological body being introduced,using feature of independent variable of gravity-magnetic field functions,taking density and susceptibility related to gravity-magnetic func-tion as default parameters of model,the deterministic model is established owing to better solution to the con-tradictioc of difficulty in identifying strata and less test analytical data for density and susceptibility in newly explored area;third,under assumption of independent parent distribution,a real modeling by strata,the prob-lem of difficult plane closure arising in profile modeling is avoided,This technology has richer and more detailed fault and strata information than sparse pattern seismic data in newly explored area,successfully inverses and plots structural map of Indosinian discontinuty in Hefei basin with combined gravity-magnetic-electric-seismic inversion,With development of high precision gravity-magnetic and overall geophysical technology,it is certain for introducing new methods of stochastic modeling and computational intelligence and promoting the develop-ment of combined gravity-magnetic-electric-seismic inversion to open a new substantial and promoting the develop-ment of combined gravity-magnetic-electric-seismic inversion to open a new substantial path.     

Development of Geological Data Warehouse

Data warehouse (DW), a new technology invented in 1990s, is more useful for integrating and analyzing massive data than traditional database. Its application in geology field can be divided into 3 phrases: 1992-1996, commercial data warehouse (CDW) appeared; 1996-1999, geological data warehouse (GDW) appeared and the geologists or geographers realized the importance of DW and began the studies on it, but the practical DW still followed the framework of DB; 2000 to present, geological data warehouse grows, and the theory of geo-spatial data warehouse (GSDW) has been developed but the research in geological area is still deficient except that in geography. Although some developments of GDW have been made, its core still follows the CDW-organizing data by time and brings about 3 problems: difficult to integrate the geological data, for the data feature more space than time; hard to store the massive data in fifferent levels due to the same reason; hardly support the spatial analysis if the data are organized by time as CDW does. So the GDW should be redesigned by organizing data by scale in order to store mass data in different levels and synthesize the data in different granularities, and choosing space control points to replace the former time control points so as to integrate different types of data by the method of storing one type data as one layer and then to superpose the layers. In addition, data cube, a wide used technology in CDW, will be no use in GDW, for the causality among the geological data is not so obvious as commercial data, as the data are the mixed result of many complex rules, and their analysis needs the special geological methods and software; on the other hand, data cube for mass and complex geo-data will devour too much store space to be practical. On this point, the main purpose of GDW may be fit for data integration unlike CDW for data analysis.     

应用区域地基全球定位系统观测分析北京地区大气总水汽量

利用2000年6月1日～8月11日北京地区地基全球定位系统(Globe Positioning System)网遥感大气总水汽量试验的观测资料,分析了北京地区夏季大气总水汽量的时空变化,研究了大气总水汽量与日平均温度、地面水汽压和降水的关系.研究结果表明:大气总水汽量存在明显的时空变化,对于地理位置基本相近的台站,海拔高度的影响比较明显,一般情况下高山站的水汽总量低于平原站;在晴天,地面水汽压与大气总水汽量有较好的相关性,而在云雨日,由于高低层大气湿度的变化常常不同步,用地面水汽压估算的大气总水汽量具有较大的偏差;大气总水汽量短时间内的快速增加往往对应有降水过程出现,但总水汽量的大小与降水量之间并没有明显的相关,在降水预报中应综合考虑总水汽量的前期平均水平、短时的增幅和峰值大小等条件的影响.     

黄河流域夏季分区面雨量预报研究

介绍黄河流域分区夏季面雨量预报的研究成果，精心挑选51个具有较好代表性的测站对黄河流域夏季降水的时空演变特征进行分析，使用K均值动态聚类对黄河流域的夏季降水进行了客观分区，并计算出各流域夏季面雨量。通过对黄河流域夏季雨量与500hPa环流，海温、OLR、中纬阻高，高原积雪，欧亚积雪等重要影响因子的关系分析，结合黄河流域夏季面雨量年降和年代际演变特征的分析，研究出黄河流域分区夏季面雨量预测的基本方法和模型，并通过客观化的数学方法建立黄河流域夏季面雨量预测系统，预测系统十年回报的结果显示出具有较的预测技巧。     

三江源生态环境监测研究

青海省生态环境监测系统主要由遍布全省各典型生态系统区的生态环境监测站网、卫星遥感信息接收处理系统，信息收集、处理、模拟、评价系统，综合信息服务与反馈等部分组成。建立环境监测系统的目的是对青海省的生态环境进行系统监测和评估，及时为各级政府、有关部门和公众提供准确、全面的生态环境监测信息，为生态环境保护和建设提供科学依据。青海省生态环境监测系统于2003年5月1日开始业务运行，目前尚处于起步阶段。