Stratigraphy,type and formation conditions of the late precambrian banded iron ores in south China

Based on research on the “Xinyu-type” Sinian iron deposits in Jiangxi Province and metamorphosed iron deposits in Jiangkou and Qidong of Hunan, Sanjiang and Yingyangguan of Guangxi, Longchuan of Guangdong and some other areas in Fujian, the authors have come to the following conclusions:

1. The metamorphosed late Precambrian iron ores widespread in south China may be roughly assigned to two ore belts, namely the Yiyang-Xinyu (Jiangxi)-Jiangkou(Hunan)-Sanjiang (Guangxi) ore belt or simply the north ore belt, and the Songzheng(Fujian)-Shicheng (Jiangxi)-Bailing (Longchuan of Guangdong)-Yingyangguan (Guangxi) ore belt or the south ore belt. Tectonically, the former lies along the southern margin of the “Jangnan Old Land”, while the latter along the northwestern border of the “Cathaysian Old Land”.
2. Iron deposits of this type occur exclusively in the same interglacial horizon of the Sinian Glaciation in south China. Above and below the ore bed there lie the glacial till-bearing volcanic-sedimentary layers.
3. Based on sedimentary features, the iron formations can be divided into four types: silica-iron-basalt formation, silica-iron-clastic rock formation, silica-iron-tuff formation and silica-iron-carbonate rock formation, which progressively grade into each other.
4. Iron ores were formed at the late stage of late Proterozoic rifting in neritic environments, with their distribution governed by the rift valleys on the margins of the “Jiangnan Old Land” and “Cathaysian Old Land”. Consequently, intense mafic volcanism as well as weathering and denudation of palaeocontinent during rifting provided material sources for the formation of iron deposits. Meanwhile, warm and humid stationary neritic environment during the south China great glacial period constitutes favorable palaeoclimatologic and palaeogeographic conditions for the deposition of iron ores.
5. The iron formations have undergone regional metamorphism of greenschist-amphibolite facies.

To sum up, the late Precambrian banded iron ores should be of metamorphosed volcano-sedimentary type.     

北京地区地壳Q值随深度的分布特征

地震波在介质中的衰减,是介质的重要特性之一,而Q值则是衡量衰减特性的主要物理参数,称之谓介质的品质因子。根据文献[1]提出的方法,用北京台网记到的近震直达P波资料,测定北京地区的大量Q值表明:Q值与P、S波到时差(t_s—t_p)有关;(t_s—t_P)大,测得的Q值也大;(t_s—t_P)小,测得的Q值也小。这种现象在朱传镇、李兴才     

七十年代全球地面气温的初步研究(二)——七十年代全球地面气温的变率和主要变率中心影响的传播

本文计算分析了七十年代全球地面气温变率的时空变化特征。发现全球有三个最大的变率中心:欧亚大陆中部、南极洲和赤道中东太平洋。它们的位置和强度有一定的季节变化。这些区域的温度变化与全球温度的异常有密切的联系,除了直接向周围一定区域扩展外,它们可能以三种主要方式向其它地区传播:(1)纬向温度距平波;(2)经向温度距平波;(3)“经向温度通道”。 因此可以认为,这些地区是全球气候变化的灵敏点,并可能成为异常气候的源地。我国特别是东北地区的温度异常与最大变率中心的温度变化有相当密切的联系。 有意思的是,这三个最大变率中心都位于地球大气的主要热汇区,下垫面热力状况可能是它们形成的一个重要原因。     

Morphological peculiarities of synthesized diamonds and a preliminary discussion on the region for perfect diamond crystal growth

Crystal habit and morphological peculiarities of synthetic diamonds at various temperatures and pressures have been studied. A diagram has been proposed based on experimental data for different crystal morphologies with respect to differentT-P conditions. A preliminary discussion has been given to the growth field of perfect crystals and a principle is presented for the optimumT-P conditions for synthesis of perfect diamonds.     

海南什统萤石矿床地质特征

什统萤石矿床位于海南省白沙拗陷带与五指山隆起的接触部位,是以断裂控矿为主的大型萤石矿床,其容矿构造为NE向张扭性断裂,成矿围岩为二长花岗岩和结晶灰岩.笔者以现场地质事实为依据,细致地研究该区的矿床地质特征,为今后的萤石矿床地质探矿提供了理论依据.     

五十年创业成果丰硕继承伟业再创辉煌--纪念北京矿产地质研究院成立五十周年

52年前,1955年6月18日北京矿产地质研究院宣告成立,开始了创新创业的历程.     

Vulnerability of groundwater in Quaternary aquifers to organic contaminants: a case study in Wuhan City,China

More than 30 organic contaminants were detected in shallow groundwaters at Wuhan, the largest city in central China. Seriously contaminated groundwaters were from densely populated, industrial and commercial areas. Abnormal concentrations were found in groundwater from Hankou, downtown Wuhan: trimethylbenzene up to 29 μg/L, tetramethylbenzene up to 866 μg/L, and trichloroethene up to 9.5 μg/L. Benzene, Toluene, Ethylene and Xylene (BTEX) contamination of groundwater is serious and widespread at Wuhan, ranging between 0.14 and 25.0 μg/L. Considering the hydrogeological conditions of most Chinese cities, DRAMIC, a modified version of the widely used DRASTIC model, was proposed by the authors for assessing vulnerability of groundwater to contamination. The factors D, R, A and I in DRAMIC model are the same as in DRASTIC. The factor topography is ignored. The factor soil media is substituted by a new factor aquifer thickness (M) and the factor hydraulic conductivity of the aquifer by a new factor impact of contaminant (C). The equation for determining the DRAMIC Index is: DRAMIC = 5D _R + 3R _R + 4A _R + 2M _R + 5I _R + 1C _R. The calculated DRAMIC Index can be used to identify areas that are more likely to be susceptible to groundwater contamination relative to each other. The higher the DRAMIC Index is, the greater the groundwater pollution potential. Applying DRAMIC, a GIS-based vulnerability map for Wuhan city was prepared. Interestingly, places such as downtown Hankou, where enhanced concentrations of BTEX have been detected, correspond quite well with those with higher DRAMIC ratings.     

A new fault rupture scenario for the 2003 Mw 6.6 Bam earthquake, SE Iran: Insights from the high-resolution QuickBird imagery and field observations

The December 26, 2003 M_w 6.6 Bam earthquake is one of the most disastrous earthquakes in Iran. QuickBird panchromatic and multispectral satellite imagery with 61 cm and 2.4 m ground resolution, respectively provide new insights into the surface rupturing process associated with this earthquake. The results indicate that this earthquake produced a 2–5 km-wide surface rupture zone with a complex geometric pattern. A 10-km-long surface rupture zone developed along the pre-existing Bam fault trace. Two additional surface rupture zones, each 2–5 km long, are oblique to the pre-existing Bam fault in angles of 20–35°. An analysis of geometric and geomorphic features also shows that movement on the Bam fault is mainly right-lateral motion with some compressional component. This interpretation is consistent with field investigations, analysis of aftershocks as well as teleseismic inversion. Therefore, we suggest that the 2003 Bam earthquake occurred on the Bam fault, and that the surface ruptures oblique to the Bam fault are caused by secondary faulting such as synthetic shears (Reidel shears). Our fault model for the Bam earthquake provides a new tectonic scenario for explaining complex surface deformations associated with the Bam earthquake.     

基于Flash技术的专业互动多媒体网络地图的构建

在介绍专业互动多媒体网络地图及Flash技术特点的基础上，分析利用Flash技术构建专业互动多媒体网络地图的解决方案，并着重讨论在Flash技术支持环境中地图数据在客户端与服务端的获取与组织方式，以及实现地图信息查询的方法。     

地球质心运动的频谱分析方法

针对地球质心运动主要是由多种周期运动叠加的特点，依次讨论了谱分析方法中的AR模型谱分析和小波谱分析方法，分别指出：将参数谱分析方法中的AR模型谱分析和非参数谱分析中的小波谱分析相结合产生的小波－AR谱分析以及小波包－AR谱分析方法，在地球质心运动的谱分析中有较好的频率分辨率以及噪声抑制能力。