Carbon–oxygen isotopic covariations of calcite from Langdu skarn copper deposit,China: implications for sulfide precipitation

The Langdu skarn copper deposit in the Zhongdian area, Yunnan Province, China, has an average Cu grade of 6.49 %. The deposit is related to a porphyry intrusion(*216 Ma), which was emplaced in the Upper Triassic sedimentary rocks of the Tumugou and Qugasi Formations.At the Langdu skarn copper deposit, carbon and oxygen isotope ratios of fresh limestones(d18O = 3.0–5.6 % relative to V-SMOW; d13 C = 24.5–25.7 % relative to PDB)and partly altered limestones(d18O = 27–7.2 to-1.9 %;d13C = 11.8–15.2 %) indicated that the deposit was a typical marine carbonate source. Oxygen and carbon isotope values for calcites formed at different hydrothermal stages are-9.1 to 0.2 and 10.1–16.3 %, respectively. Moreover,the carbon–oxygen isotopic composition of an ore-forming fluid(d18O = 5.0–9.5 %, d13 C =-7.3 to-5.3 %) suggested the presence of magmatic water, which most likely came from the differentiation or melting of a homologous magma chamber. The deposition of Calcite I may arise from metasomatism in an open system with a progressively decreasing temperature.Later, the minerals chalcopyrite, pyrrhotite, quartz and Calcite II were precipitated due to immiscibility. Water–rock interaction could potentially be responsible for Calcite III precipitation in the post-ore stage.     

Pressure Evolution and Hydrocarbon Migration-Accumulation in the Moliqing Fault Depression,Yitong Basin,Northeast China

The Yitong(伊通) basin is a Late Mesozoic and Cenozoic continental sedimentary basin in Northeast China.On the basis of well tests and seismic data,we use the 2D modeling technique to rebuild the pressure evolution and hydrocarbon migration in the Moliqing(莫里青) fault depression of the Yitong basin.Based on the modeling results,four conclusions are drawn as follows.(1) The Eocene Shuangyang(双阳) Formation within the Moliqing fault depression had entirely undergone three epi-sodic cycles of pressure accumulation...     

Effect of Agents on Hydrate Formation and Low-Temperature Rheology of Polyalcohol Drilling Fluid

In order to ensure safe drilling in deep water and marine gas hydrate bearing sediments,the needed characteristics of drilling fluid system were analyzed.Moreover,the effect of different agents on hydrate formation and the low-temperature rheology of designed polyalcohol drilling fluid were tested,respectively.The results show that clay can promote gas hydrate growth,while modified starch and polyalcohol can inhibit hydrate formation to some extent,and PVP K90 has a good performance on hydrate inhibition.Th...     

东营凹陷沙四上亚段滩坝物源体系

滩坝是东营凹陷沙四上亚段的一个重要沉积体系。根据岩石中岩屑组分的类型及组合特征、砂岩成分成熟度、砂体展布方向及古地理格局等对东营凹陷沙四上亚段进行了物源体系的研究。研究区存在9大物源体系,其中广饶凸起、鲁西隆起、滨县凸起和高青三角洲为滩坝的形成提供了物源。根据物源与滩坝的关系,将研究区划分为基岩-滩坝物源体系、正常三角洲-滩坝物源体系、扇三角洲-滩坝物源体系;由于物源的性质、供给强度的不同,造成滩坝在宏观展布和储层特征上存在明显差异。     

Phytogeographic and Syntaxonomic Diversity of High Mountain Vegetation in Dinaric Alps (Western Balkan,SE Europe)

The high alpine and subalpine vegetation of Dinaric Alps is very diverse.These are conditional on genuine patterns of development of the geological substrate,climate,soil and terrain on the mountain world,which are interconnected and spatially,and ecologically away.Also,today high mountain vegetation is extremely important indicator of global changes.In this area are many refugia of glacial biodiversity.Very illustrative example for understanding the specific forms of ecological diversity is high alpine veg...     

MIXTURE ANALYSIS USING FACTOR ANALYSIS.Ⅱ:SELF-MODELING CURVE RESOLUTION

One of the major applications of factor analysis in the chemical literature,self-modeling curve resolution(SMCR),is covered in this review,including a historical account of the inethods derived from Lawtonand Sylvestre's original method.Papers treating the theory or applications of SMCR are included.Qualitative and quantitative applications are described where appropriate.     

Spatial prediction of landslide for Badong County in the ThreeGorges reservoir district

By using the landslide risk evaluating model and the advantages of GIS technology in image processing and space analysis, the relative landslide hazard and risk evaluating system of the new county site of Badong is built up. The system is mainly consisted of four subsystems： Information management subsystem, hazard as- sessment subsystem, vulnerability evaluation subsystem and risk prediction subsystem. In the system, landslide hazard assessment, vulnerability evaluation, risk predictions are carried out automatically based on irregular units. At last the landslide hazard and risk map of the study area is compiled. During the whole procedure, Matter-Element Model, Artificial Neural Network, ancl Information Model are used as assessment models. This system provides an effective way for the landslide hazard information management and risk prediction of each district in the Reservoir of Three Gorge Project. The result of the assessment can be a gist and ensure for the land planning and the emigration project in Badong.     

Growth of a polymetallic nodule from northwestern continental margin of the South China Sea and its response to changes in paleoceanographical environment of the late Cenozoic

In the northern South China Sea,the accumulation of enormous quantities of terrigenous sediment during Cenozoic rendered well-developed polymetallic nodules very rare.In this study,we analyzed a polymetallic nodule from the northwestern continental margin of the South China Sea using microscopic mineralogical observation,electron probes,X-ray diffraction(XRD),ICP-MS,and Be isotope dating.We found the nodule’s shell layers rich in different types of microstructures,including columnar,laminar,stack-like,petal-like,and porphyritic structures.The major mineral components of the nodule are MnO2.Unlike nodules from the eastern Pacific basin,this nodule has high contents in Fe,Si,Al,and REEs but low contents in Mn,Cu,Co,and Ni.The Mn/Fe ratio is also low and the average REEs content is 1370.4 ppm.There is a strong positive anomaly of Ce;and the Be(beryllium) isotope dating shows the initial time of growth of the nodule to be about 3.29 Ma.The inner compact layer formed from 3.29 Ma to about 1.83 Ma.The laminar and stack-like structures and the low contents of the terrigenous elements such as Fe,Si,REE,and Al indicate the paleoceanographical environment with weak undersea currents and favorable oxidizing conditions.From 1.83 Ma to 0.73 Ma,the growth rate of the nodule increased by about 3%;the microstructures formed during this period are stack-like and columnar.The contents of Si and Al are increased by nearly 10%,indicating an increase of terrigenous sediment input in the northern South China Sea.The content of Ce is decreased by about 16%,indicating a significant weakening of the oxidizing conditions at the seabed.From 0.73 Ma to 0.69 Ma,the growth rate of the nodule rapidly rose up to 8.27 times that of the nodule’s average growth rate,and the contents of Fe,Al,and REEs in the layer also increased,forming a loose layer characterized by oolitic,granular,porphyritic,and petal-like structures,indicating the paleoceanographical environment with a high sedimemtation rate and abundant supply of terrigenous sediment in the northern South China Sea.From 0.69 Ma to 0.22 Ma,the growth rate of the nodule suddenly slowed and the outer compact layer formed.Contents of Fe,Si,REE,Al,Mn,Cu,Co,and Ni in this layer were significantly lower than in other layers.The main structures of the layer are laminar and fissure filling structures.These reflect the paleoceanographical environment with stable undersea currents,poor oxidizing conditions,and other conditions not conducive to nodule growth.The growth process of nodule S04-1DG-1 was found to respond sensitively to the changes of the paleoceanographical environment of the northern South China Sea during the late Cenozoic.     

利用样本排序方法比较化探异常识别模型的效果

地球化学异常的有效识别是化探找矿成败的关键环节.利用样本排序方法对各种化探异常识别模型的处理效果和优劣性进行了比较.以云南个旧及其周边地区铜元素水系沉积物为例, 应用元素含量、异常衬度、局部奇异性分析三大类方法对数据进行了处理, 对化探异常指示变量的排序值进行了3个方面的对比: (1) 在高背景区和低背景区样品的排序特征; (2) 有矿出现位置处样品的样本排序特征; (3) 累积面积(等效于上侧样本排序值) 不同分组所圈定的异常范围和矿床(点) 之间的空间相关性.结果表明, 局部奇异性分析方法较按含量高低的全局性方法对弱缓异常识别更为有效, 也相对优于滑动衬值.按奇异性指数基于证据权法圈定的异常远景区更具预测意义, 显著优于用元素含量值所圈定的异常范围.局部奇异性方法原理清晰、方法简便、可操作性强, 在地球化学异常识别中可以用其替代滑动衬值方法.      

甘肃玛曲大水金矿成矿过程中资源量生长的数量规律

大水金矿床是著名的超大型矿床.在借鉴前人矿床地质研究成果的基础上, 通过对矿体规模数据的多重分形特征及吨-品位关系研究, 揭示了成矿过程中资源量生长的数量规律.矿体长度服从简单分形分布, 矿床资源量的吨-品位关系能用指数函数或直线方程更好地拟合, 矿床与矿体资源量双对数图、吨-品位的双对数图的多重分形特征表明: 在分形构造成矿空间中, 特定成矿阶段的矿床资源量的生长方式是自组织非线性增殖过程, 与自组织有关的随机性使吨-品位关系趋于指数关系; 在整个成矿过程中, 矿床资源量的生长方式是各阶段矿体资源量的线性叠加.进一步根据熵最大化原理及效用理论导出了与统计结果吻合的矿床吨-品位方程, 并得到柴家庄金矿矿体地质数据的验证.