广西平桂地区锡矿土壤离子电导率异常特征和离子成分及找矿预测

为了解广西平桂地区锡矿土壤离子电导率异常特征,研究不同种类离子的含量变化关系对电导率的贡献大小,为解释锡矿土壤离子电导率异常的形成机制提供理论依据。对广西平桂地区锡矿的土壤离子电导率异常进行研究,结果表明：①在已知锡矿体上测出了清晰的土壤离子电导率异常,异常形态呈典型双峰形态“兔耳”状或“单峰”状, 异常垂直指示锡矿体的赋存位置;②弄清了锡矿体组成土壤离子电导率异常的离子成分特征,其成分主要是SO42-、Ca2+、HCO3-、Cl-、Fe3+、Mg2+、Na+、K+、Mn2+、F-等一套水可溶性离子,经过相关分析得出锡矿土壤离子电导率异常与各种水可溶性离子的相关系数SO42-＞Ca2+＞HCO3-＞Cl-＞Fe3+＞Mg2+＞Na+＞K+＞Mn2+＞F-;③在未知区的找矿预测中找到2个具有成矿远景的土壤离子电导率异常,经深部工程验证找到了隐伏锡矿体。     

试论层状铜矿的三种主要成因模式

层状铜矿是铜矿资源中仅次于斑岩铜矿的重要矿床类型,包含多种成因机制,历来有同生与后生之争。本文归纳了这类铜矿的３种成因模式,即“沉积－成岩”、“沉积－喷气”和“沉积－改造”模式,讨论了它们的不同特征和机制,以及三者之间的相互关系。文中对“沉积－改造”模式进行了重点讨论,并强调了这一成矿作用的意义。     

Notes

There are more than 300 sediment-hosted Zn–Pb deposits and occurrences in Iran and most of them occur within carbonate rocks, including world-class deposits such as Mehdiabad, Irankuh and Angouran. To achieve a broad metallogenetic framework for carbonate-hosted (CH) Zn–Pb resources in Iran, we developed a GIS database with all reported deposits and occurrences of this affinity. From this database and the age of host rocks, two major groups of CH Zn–Pb deposits can be established and linked to different tectonic events: (a) Permian–Triassic-hosted deposits (mainly of the Mississippi Valley-type; MVT), and (b) Cretaceous-hosted deposits. The Permian–Triassic-hosted deposits are concentrated in the Central Alborz metallogenic belt, the NE margin of Sanandaj–Sirjan Zone (SSZ), and the Tabas-Posht e Badam metallogenic belt, whereas those hosted by Cretaceous carbonate rocks are distributed in the SSZ, the Yazd Block and the Central Iranian Geological and Structural (CIGS) transitional zone. In addition, the formation of numerous F-rich deposits hosted by Permian–Triassic carbonate rocks is also explained by a MVT deposit model. According to our GIS-based metallogenic maps, there is a significant correspondence between the distribution of CH Zn–Pb deposits and the main suture zones in and around the Iran Plate. Most of the orogenic Permian–Triassic-hosted MVT deposits occur along the suture zones that resulted from the collision of the Iran Plate with the Eurasia Plate when the Paleo-Tethys Ocean closed (during Upper Triassic time). The close spatial, temporal and (therefore assumed) genetic relationships between the Permian–Triassic-hosted MVT deposits and the Main-Cimmerian orogenic events reflect the development of a foreland basin during the Upper Triassic, which encompassed Zn–Pb and F mineralising processes. The modern distribution of these deposits in Iran is explained by the formation of this foreland basin, and by the subsequent (post-Upper Triassic) fragmentation of the Central Iranian Microcontinent into blocks that rotated along right-lateral strike-slip faults. This late process split the Permian–Triassic-hosted MVT province into the Tabas-Posht e Badam and the Central Alborz metallogenic belts.     

Late Holocene tsunami traces on the western and southern coastlines of the Peloponnesus (Greece)

Greece, in particular the western and southern parts close to the subduction zone of the Hellenic Trench, experiences strong earthquakes and subsequent tsunamis. Nevertheless, field evidence of tsunamis from the late Holocene is extremely rare. Our research along the coastlines of the western and southern Peloponnesus resulted in new findings of tsunami impacts in the form of clusters and ridges of large boulders and thick tsunamigenic sand layers encountered in vibracores. Many boulders contained attached marine organisms, which prove that they were transported from the foreshore environment against gravity by extreme wave events. The attached organisms, which have been dated by ¹⁴C-AMS, suggest that historical tsunami events of great energy occurred around 1300 cal AD. A wood fragment found at the base of tsunami deposits in a vibracore from Cape Punta was dated to ~ 250 cal AD.     

从第32届国际地质大会看矿床学及相关学科的进展

第32届国际地质大会中有关矿产方面的动态和进展主要分为以下4个部分：与黑色页岩有关的矿床;中亚地区的矿床及构造;锡、钨及其他稀有金属矿床的新发展;海洋矿床的最新发展。     

西昌市柳家河沟泥石流成因分析及防治

柳家河沟泥石流是近几年发生的较为典型的泥石流。通过遥感解译和野外调查,发现其发生主要受该区域地形地貌、降雨条件和物源条件影响。分析其运动特征,认为该柳家河沟依然存在发生较大型泥石流的可能。提出以拦加固为主,以防护为辅的防治方案。     

钾盐变质作用的矿物学和地球化学响应特征——以老挝沙湾拿吉钾盐盆地ZK004孔为例

通过对老挝沙湾拿吉钾盐盆地ZK004钻孔岩芯中的钾盐层段矿物学、微量元素地球化学特征的分析,探讨了钾盐变质过程的矿物学和地球化学指标的响应特征。结果表明,ZK004孔变质作用大致可分为2个阶段:第一阶段为不均匀交代阶段,该阶段光卤石层受到非海相流体淋滤,在光卤石层顶部形成次生钾石盐;第二阶段为强烈淋滤重结晶阶段,早期交代成因次生钾石盐层受到多次非海相流体的交代淋滤作用,发生溶解—重结晶乃至淋失。元素地球化学分析表明,光卤石阶段石盐中Fe、Si和Sr具有较好的峰值对应且光卤石阶段的含量高于钾石盐阶段,指示了陆相地表水的补给作用主要发生在光卤石沉积阶段,钾石盐阶段石盐中Cu、Zn等具有较好的含量峰值对应关系,表明改造次生钾石盐的流体可能主要是地下水。     

氯化物型钾盐矿床氯同位素地球化学研究

根据国内外许多钾盐矿床大量样品测定的结果：通常石盐（岩）的37Cl／35Cl比值和δ37Cl（％）值高于钾石盐（岩）；钾石盐高于光卤石（岩）。例如：西班牙Catalonia盆地钾盐矿床，其石盐岩为0．31958—0．31941和＋1．002─＋0．470‰，钾石盐岩为0．31913和─0．407‰，光卤石岩为0．31887和─1．221‰，等等。这说明了这些蒸发岩是在水体浓缩的不同阶段形成的，是氯同位素分馏作用长期不断进行的结果。其氯同位素组成与Br、K和Mg含量有着密切关系。困而在我国找钾过程中，可将氯同位素组成及Br、K、Mg含量结合起来作为找钾标志考虑。     

南极乔治王岛菲尔德斯半岛湖泊堆积物的物相组成特征及其环境意义

本文根据南极乔治王岛菲尔德斯半岛燕鸥湖、西湖和基太克湖三个堆积剖面物相组成与丰度的资料，讨论其物相组成特征、物质来源及其环境意义。研究结果表明，湖泊堆积物主要来自该岛广泛分布的火山岩。在南极地区干冷环境条件下，源区母岩所经受的风化作用以物理风化为主，化学风化微弱。高岭石、方解石丰度与年龄关系曲线在湖积层与冰碛层之间的陡削变化表明，相应的环境变化是突变式的，可能与这两种堆积物搬运方式的不同和冰碛物的保护作用有关。