西藏冈底斯成矿带东段主要钼多 金属矿床成矿规律研究

文章以钼成矿作用为主线,对冈底斯东段主要钼多金属矿床成因类型、空间分布特征进行了总结,对主要钼多金属矿床成矿时代进行了统计,识别出了5期钼成矿事件。基于前人研究成果,对主要斑岩—矽卡岩钼多金属矿床成矿岩浆岩基本地质特征、岩浆岩主量元素、稀土和微量元素、锶同位素地球化学特征进行了阐述并对比了独立钼矿、钼(铜)矿、铜(钼)矿和钼多金属矿成矿岩体特征之间的差异。通过对南冈底斯南缘至冈底斯弧背断隆带不同钼多金属矿床成矿岩体锆石Hf同位素、矿石硫化物Pb同位素的梳理阐明了成岩—成矿物质源区差异与矿化元素组合空间分带之间的耦合关系。基于冈底斯东段钼多金属矿床产出大地构造位置及其形成时代,文章最后对主要钼成矿事件的动力学背景进行了初步探讨。     

东秦岭丹凤地区黄龙庙二长花岗岩LA-ICP-MS锆石 U-Pb年龄、岩石地球化学特征及其地质意义

东秦岭丹凤地区黄龙庙含榴二长花岗岩是典型的浅色含铀花岗岩体之一。它具有高硅(73.65%~76.60%)、过铝(13.01%~13.80%,A/CNK1.0)、富钾(4.89%~6.14%)的特点,其轻重稀土元素强烈分馏,铕负异常十分发育,微量元素具有典型上地壳的含量特征。所获得LA-ICP-MS锆石U-Pb年龄为415.2±2.0Ma,是志留纪末期花岗岩。该花岗岩是在后碰撞环境下,由秦岭岩群郭庄岩组的含榴黑云斜长片麻岩部分熔融所形成的钙碱性S型花岗岩。与巴罗型区域变质作用的年龄(426Ma)一起,限定了东秦岭早古生代碰撞作用415~426Ma之间进入后碰撞构造环境,也表明早泥盆世以后的东秦岭地区并未经历大规模区域性变质变形,进入了相对稳定的地质演化阶段。     

The Origin of Paleokarst in the Huanglong Formation of the Eastern Sichuan Basin: Evidence from δ13C, δ18O and 87Sr/86Sr

Karst rocks from the Huanglong Formation exposed at the margin of the Eastern Sichuan Basin can be divided into four types:slightly corroded, moderately corroded porous, intensely corroded brecciated and intensely corroded and replaced secondary calcic karstic rocks. The carbon, oxygen and strontium isotope compositions of the various karst rocks are analyzed systematically and compared to rocks without karst corrosion. The results indicate that(1) the Huanglong Formation in the eastern Sichuan Basin was a restricted bay supplied and controlled by freshwater in which mudmicrite and mud-dolomicrite exhibit low δ13C and δ18O values and high 87Sr/86 Sr ratios;(2) all types of karstic rocks in the paleokarst reservoirs of the Huanglong Formation in the research area are affected by atmospheric freshwater with the δ13C and δ18O values and 87Sr/86 Sr ratios in the original formation approaching those of atmospheric freshwater, which reflects ancient hydrological conditions, fluid properties, isotopic source and the fractionation effect;(3) the intensely corroded and replaced secondary limestone is affected by a variety of diagenetic fluids, often reflected by δ13C and δ18O values, while the 87Sr/86 Sr ratios exhibit the strong degree of the corrosion;(4) after comparing the 87Sr/86 Sr ratios of each type of karst rock, the diagenetic fluids are determined to be mainly atmospheric freshwater, and depending on the strength of corrosion, and the low 87Sr/86 Sr ratio fluids in the layer will participate in the karst process. The carbon, oxygen, and strontium isotopes of different karstic reservoirs can provide meaningful geochemical information for forecasting and evaluating the development and distribution rules of the Huanglong Formation at the margin of the eastern Sichuan Basin in time and space.     

滨里海盆地东缘构造演化及油气成藏模式分析

滨里海盆地是中亚地区油气资源最为丰富的沉积盆地之一。本文以油气地质理论为指导,对盆地东缘的构造演化以及其油气成藏组合进行分析,认为乌拉尔造山运动对盆地东缘的构造演化造成了深刻影响。盆地东缘盐上层系的生烃条件较差,主要油气来源应为盐下层系。石炭系碳酸盐岩KT-I层和KT-II层是盆地东缘发育的良好储层。下二叠统盐层为区域性盖层,特别是对盐下油气藏起到了良好的区域封盖效果,盐相关构造圈闭类型发育。不整合面、断层和孔、洞、缝等组成复合的油气输导体系。盆地东缘的油气成藏模式主要为盐下层系的"自生自储型"和"下生上储型"以及盐上层系的"下生上储型"。     

陇东巨厚黄土塬区地震勘探数据采集方法研究

陇东巨厚黄土塬区,由于表层地震激发条件复杂多变,潜水面深,反射波衰减强烈,导致目的层反射波难以分辨,为此在陇东地区的多个地震勘探项目中有针对性的进行了多井组合、井深对比、检波器组合等一系列试验及分析研究。结果表明在黄土塬地区可使用中密度成型炸药,多井组合激发,且井越深记录质量越好;检波器采用9串2并或9串线形组合,组内距2m,可有效压制随机干扰;观测系统须根据不同地貌条件进行选择,在黄土塬上宜采用多道、小炮间距、小偏移距、高覆盖等直线观测系统;而在黄土沟、坡中,可采用弯线观测系统,并适当减少道数及覆盖次数、增大炮间距及偏移距等;在沟塬过渡段为避免出现空白段,应采用变观系统。     

Structural Analysis of the Multi-layer Detachment Folding in Eastern Sichuan Province

<正>A serial of"comb-like and trough-like"folds developed in eastern Sichuan,controlled by the multi-layer detachment folding,is different from the classical Jura-type structure in their development.The key factor resulting in the development of these structures is the occurrence of detachment layers in different parts of Neoprotozoic to Mesozoic stratigraphy of study area,which, from the bottom to the top,are the lower part of Banxi Group,Lower Cambrian(Niutitang Formation),Lower Silurian(Longmaxi Formation and Luoreping Formation),Upper Permian (Wujiaping Formation) and Lower Triassic(Daye Formation).On the basis of field survey combined with sand-box modeling,this study argued that the detachment layer of the lower part of Banxi Group controlled the development of the"comb-like"folds,and the lower part of Cambrian detachment layer controlled the development of"trough-like"folds.Because of several detachment layers occurring in the study area,the development of duplex structures different scales is an important deformation mechanism,and the duplexes are the important structures distinguished from the typical detachment folding structures.Due to these duplexes,the surface structures and structural highs may not be the structural highs in the depth.Meanwhile,the detachment layers are good channels for oil/ gas migration benefiting the understanding of accumulation and migration of oil and gas.     

福建东部近海生物中稀土元素的生态化学特征

在福建东部海域16个海湾采集了近海生物鱼、虾、贝壳、藻4大类26小类128个样品,用ICP-MS法测定15种稀土元素的含量,结果表明,轻、重稀土元素存在较大的分镏作用,明显富集轻稀土元素,即轻稀土元素的生物学效应更为明显,鱼类等近海生物稀土元素配分模式总体上与海水和世界页岩稀土元素配分模式接近。稀土元素沿福建东部海域食物链的迁移传递没有表现出明显的生物放大作用。     

东秦岭地区钼矿床研究现状及存在问题

秦岭造山带北部和华北地台南缘的豫西地区是中国重要的钼多金属和贵金属成矿带之一。前人的研究认为该区钼矿床形成于233～221Ma、148～138Ma和131～112Ma等3期。本文通过对研究区的钼矿床类型及其产出的大地构造环境、岩浆岩类型及时代以及钼矿床形成年代等方面的总结,认为233～221Ma时期的钼矿床产于陆内拉伸环境,可能与同期碱性岩体有关。从Pb、Sr、Nd同位素组成看,成矿物质可能来源于秦岭造山带中的东坡组,成矿元素组成相对简单,以伴生Pb和Au为特征。148～138Ma期间的钼矿床可能形成于地壳加厚的过程中,其形成与以地壳物质为主的重熔型或I型钙碱性岩体有关,岩体Sr、Ba含量较高,伴生成矿元素主要为Fe和W。131～112Ma时期的钼矿床形成于地壳减薄的环境中,与中国东部岩石圈的拆沉、软流圈上涌等过程有关的钾质、高钾或碱性花岗质岩石相关,成矿元素组合局部富W。     

四川东部华蓥山三叠系海相碳酸盐岩对海水信息的保存性评估

海相碳酸盐成岩蚀变及其对海水信息保存程度的认识与评估在古海洋学和沉积地质学等学科领域研究中有着重要意义,尤其对于沉积地球化学和化学地层学等方面的研究是必不可少的基础工作。笔者通过对四川东部华蓥山仰天窝剖面三叠系海相碳酸盐岩样品的微观组构观察、阴极发光和微量元素等分析表明,大多数的样品保留了较好的原始沉积组构,具有极弱和弱的阴极发光强度、较低的Mn含量和较高的Sr含量,同时也具有较小的Mn/Sr值。只有6个样品被认为遭受了较大的成岩蚀变而对海水信息的保存程度较差,需要被剔除,而大多数的样品只遭受了较小的成岩蚀变作用,较好地保留了当时海水的信息,仍然在很大程度上代表了当时的海水。     

Groundwater quality in Mesogea basin in eastern Attica (Greece)

Studies on the hydrogeological conditions of the Mesogea basin in east Attica reveal that the aquifers developed on the post‐alpine formations at the inner part of the coastal brackish zone exhibit positive hydraulic head. These Neogene and Quaternary deposits present high salt concentrations. Selected points were sampled (total 85: 51 wells and 34 boreholes) in order to obtain hydrogeological and hydrochemical data for a better understanding of the structure, operation and dynamics of the aquifer of the area. Statistical methods, R‐mode factor analysis and scatter‐plot diagrams were used for the hydrochemical analysis and presentation of the data. The groundwater resources are relatively weak and there is significant quality degradation due to the geological structure of the greater area, as well as the bad management of the aquifer and anthropogenic activities. Groundwater is characterized by high salt concentrations. Electrical conductivity values range between 260 and 6970 µS cm^?1. High salt concentrations at the coastal aquifers are due to sea intrusion, whereas they are attributed to the dissolution of minerals of the geological environment in the inland area. The groundwaters of the study area can be classified into five water types: Ca–HCO₃, Mg–HCO₃, Na–HCO₃, Na–Cl and Mg–Cl. They are saturated in dolomite and calcite, whereas they are unsaturated in anhydrite. High ion concentrations, e.g. ] (0‐221 mg l^?1), ] (0·01‐1·88 mg l^?1), ] (0·01‐6·75 mg l^?1), as well as high heavy metals concentrations are attributed to anthropogenic impacts. Copyright © 2006 John Wiley & Sons, Ltd.