西藏列廷冈铁多金属矿床磁铁矿元素地球化学特征及地质意义

西藏列廷冈矿床是林周盆地Fe-Mo-Cu-Pb-Zn矿集区内近年来新发现不久、规模较大的矽卡岩型铁多金属矿床。矿区磁铁矿发育,主要包括块状、浸染状和脉状3种类型。基于详细的野外地质调查和室内矿相学研究,将矿床成矿期划分为矽卡岩期和热液期2期,进而划分为5个成矿阶段:早期矽卡岩阶段、退化蚀变阶段、早期热液阶段、石英-硫化物阶段和碳酸盐阶段,其中,块状磁铁矿主要形成于退化蚀变阶段,浸染状和脉状磁铁矿主要形成于早期热液阶段。以磁铁矿为主要研究对象,采用电子探针(EPMA)和单矿物微量稀土元素ICP-MS分析实验,重点对磁铁矿元素地球化学特征、成因矿物学进行系统研究。研究结果表明,3种不同类型磁铁矿内均含Ti、Si、Ca等次要元素以及Na、K、Cr、Ni、Co、Pb、Ba、Sn、Sr、Sb、Cu等多种可检测到的微量元素,且矿物内主要发生了Al、Mg、Mn等元素的类质同像置换,综合TiO_2-Al_2O_3-MgO、TiO_2-Al_2O_3-(MgO+Mn O)和(Ca+Al+Mn)-(Ti+V)、Ni/(Cr+Mn)-(Ti+V)等多种磁铁矿成因判别图解投图结果及矿体野外宏观地质特征,表明矿区磁铁矿均为热液成因。块状磁铁矿具明显的Eu正异常,浸染状和脉状磁铁矿具Eu负异常,均无明显Ce异常特征,表明富Eu成矿流体在矽卡岩期的高温氧化环境下形成了矽卡岩型块状磁铁矿体,在热液期则逐渐转变为低温还原环境,形成浸染状和脉状磁铁矿及多种金属硫化物,且铁的物质来源主要与矿区花岗闪长岩和花岗斑岩紧密相关。     

老挝帕莱通铁矿床西矿段磁铁矿地球化学特征及其成矿意义

帕莱通铁矿床是老挝万象—呵叻中新生代盆地中最大规模的铁矿床,分为东、西2个矿段,西矿段为豆状、块状富磁铁矿矿体,东部则主要发育角砾状贫赤铁矿矿体。其中,西矿段主要产于新生代富铁质玄武岩中。文章对西矿段中豆状、块状磁铁矿进行了详细的野外地质调查和显微结构分析,发现块状磁铁矿具有细粒他形结构特征,豆状磁铁矿具有球粒同心圆状结构特征。对较为新鲜的磁铁矿进行电子探针(EPMA)以及激光剥蚀电感耦合等离子质谱(LA-ICP-MS)分析显示:帕莱通铁矿床磁铁矿TiO_2-Al_2O_3-MgO三角图落入岩浆岩区域;微量元素富集V、Ti、Cr、Co、Ni及Ga等元素,亏损Sr、Ba及Mg等不相容元素;w(Co)和w(Ni)较高,且较高的Ni/Co比值可以反映成因与深源物质;w(Ti)较高且Ni/Cr比值≤1,在Ti-Ni/Cr图中落入了热液型磁铁矿的范围;Ga-Sn图解表明磁铁矿属于斑岩型热液成因;(Ca+Al+Mn)-(Ti+V)或Ni/(Cr+Mn)-(Ti+V)成因判别图显示该矿床兼具Kiruna型和斑岩型矿床的特征;w(V)表明磁铁矿在较低氧化环境中形成;(Al+Mn)-(Ti+V)形成温度判别图表明磁铁矿形成温度处于300～500℃范围内。文章认为帕莱通铁矿床成矿物质主要源于岩浆演化作用形成的富铁流体,后期由于岩浆热液流体的交代作用,使得磁铁矿具有了热液成因的特征。岩浆型矿床类型在老挝及邻区分布较为广泛,研究帕莱通铁矿的成因,对于总结区域成矿规律,指导同类型矿床找矿预测具有重要意义。     

滇东南都龙锡锌铟多金属矿床磁铁矿矿物化学组成特征及其对成矿作用的约束

都龙锡锌铟多金属矿床位于著名的滇东南钨锡多金属成矿区之老君山矿集区,成矿与白垩纪大规模花岗岩活动关系密切,沿隐伏花岗岩接触带周边发育石榴子石、透辉-透闪石等矽卡岩蚀变和条带状(似层状)、脉状(囊状)的锡石、闪锌矿及磁铁矿、辉钼矿、黄铁黄铜矿等矿化,形成超大规模的岩浆热液-矽卡岩成矿系统。野外观测及研究发现,早期(矽卡岩期)高温阶段形成的磁铁矿可分为I阶段交代型磁铁矿(I-Mag)和II阶段充填型磁铁矿(II-Mag)两类:前者多呈囊状、条带状,与矽卡岩矿物共生;后者为脉状,与金属硫化矿物共生。利用ICP-AES、ICP-MS对两类磁铁矿进行主、微量元素测试,从I-Mag到II-Mag,Si、Ca、Mn及ΣREE、Pb、Zn、Ti含量增加,Mg及Sn、W、In、V、Cr、Ga含量减少,REE配分型式也由平缓向右倾的逐渐变化。TiO 2-Al 2 O 3-(MgO+MnO)、(Ti+V)-(Ca+Al+Mn)、Ni/Cr-Ti、(Ti+V)-Ni/(Cr+Mn)成因判别图解表明,磁铁矿属岩浆热液-矽卡岩成因类型;Ti、V与Zr、Hf、Nb、Ta,以及Y/Ho(24~3414)、Ni/Co(<2→>2)、Ti/V(<25→>25)、Hf/Zr(003~006→004~005)存在着线性关系和规律变化特征,指示两类型磁铁矿具有相同的物质来源,为同一成矿过程不同阶段的产物。而代表成矿流体REE组成的II-Mag的REE组成继承了老君山花岗岩REE配分趋势和Eu负异常特征,表明磁铁矿与白垩纪老君山花岗岩具有一致的物质来源。Cr-V、(Ti+V)-(Al+Mn)、Ga-Mg及Ga-Sn图解显示相同的成因类型和一致的线性关系,指示磁铁矿主体形成于较高氧逸度和温度(约300℃)的成矿环境下,并且从I-Mag到II-Mag,存在着氧逸度逐渐升高、温度逐渐降低的演化趋势。     

鄂东程潮铁矿床磁铁矿的微量元素组成及其矿床成因意义

程潮铁矿床是长江中下游成矿带最大的矽卡岩型铁矿床,位于鄂东南矿集区北缘,矿体主要产于鄂城杂岩体与下三叠统大冶组碳酸盐岩的接触带。本文报道程潮铁矿床不同产状磁铁矿的LA-ICPMS(激光剥蚀等离子体质谱)微量元素分析结果,以讨论磁铁矿的微量元素组成和变化规律及其与成矿环境的关系,为深入认识程潮铁矿床的矿床成因及成矿演化提供重要制约。研究结果显示,程潮铁矿床与成矿有关岩体(花岗岩)中的岩浆磁铁矿(副矿物)与内矽卡岩和外矽卡岩中的热液磁铁矿在显微结构和微量元素组成上具有显著差异。花岗岩中的磁铁矿不发育环带,也没有遭受后期热液的交代。内矽卡岩以发育具有振荡环带的富Si磁铁矿为特征,而外矽卡岩中的磁铁矿则以无明显环带的富Mg磁铁矿为主。内矽卡岩和外矽卡岩中的原生磁铁矿都遭受了广泛的热液交代作用而形成次生磁铁矿,即具有明显的磁铁矿溶解-再沉淀作用。与矽卡岩矿石中的热液磁铁矿相比,岩体中的副矿物磁铁矿具有高得多的V、Ti、Ni、Cr、Co及Ga等亲铁元素(相容元素)和较低的Si、Al、Mg、Sr及Ba等亲石元素(不相容元素)。这种岩浆副矿物磁铁矿和矿石矿物磁铁矿微量元素组成的系统差异表明,程潮铁矿床属于典型的矽卡岩型矿床,而非矿浆型铁矿。另一方面,内矽卡岩和外矽卡岩矿石中的原生磁铁矿也具有明显不同的微量元素组成:前者具有较高的V、Ti、Ni、Cr、Ga、Sr和Ba等,而后者具有较高的Sn、Zn、U和Sn/Ga、Zn/V及Co/Ni比值,表明外矽卡岩中的磁铁矿受地层围岩成分的影响较大,而内矽卡岩中的磁铁矿则更多地受岩浆流体组分的控制。对原生磁铁矿和次生磁铁矿微量元素的系统分析结果表明,在磁铁矿的溶解-再沉淀过程中,内矽卡岩中的次生磁铁矿相对原生磁铁矿具有显著不同的微量元素组成,前者的Si、Al、Mg、Ti、Sr及Ga等元素含量大大降低,而Zn、V、Mn、Pb、Th及U等元素含量则升高,Co、Ni、Sn及Ba等元素基本不变。外矽卡岩中的原生磁铁矿被交代形成次生磁铁矿时,Mg、Mn、Al、Zn及Co等元素发生丢失,Pb、U、Nb及Sr等元素发生富集,而Sn和Ga的含量基本不变。根据不同产状、不同结构和不同成因磁铁矿的微量元素分析可以得出以下认识:(1)程潮铁矿床属于典型的热液成因,矿区不存在矿浆型铁矿;(2)磁铁矿的溶解-再沉淀作用使大部分微量元素发生明显亏损,少部分元素发生富集,表明流体交代对磁铁矿的微量元素组成具有显著影响;(3)对磁铁矿微量元素组成的研究可为磁铁矿及矽卡岩型铁矿床的矿床成因和成矿演化提供重要信息;对磁铁矿的原位微量元素分析必须建立在详细的显微结构研究基础上,对发生过溶解-再沉淀作用的磁铁矿,需要分别对原生和次生磁铁矿区域进行高精度、高分辨率的微量元素分析,只有这样才能对磁铁矿及含磁铁矿矿床的成因进行正确的分析和认识。     

滇中腊梅铁矿床磁铁矿地球化学特征及其指示意义

滇中腊梅铁矿床位于西南“三江”地区金沙江-哀牢山-红河富碱斑岩带中段,其矿化类型不明,成矿机制和资源潜力不清,制约了该区找矿勘查的深入研究。本次研究工作在详细的地质调查基础上,根据矿(化)体产出特征,将磁铁矿划分为正长斑岩内的豆状-星点状磁铁矿(Ⅰ-Mag)、透辉石角岩内浸染状-团块状磁铁矿(Ⅱ-Mag)和层间破碎带内脉状及囊状充填型磁铁矿(Ⅲ-Mag)3种类型。通过LA-ICP-MS原位微区成分对比,发现3类磁铁矿总体富集Ti、Mn、V、Mg、Zn及Ni,贫Sn、Ga及Sc等元素,并且从Ⅰ-Mag→Ⅱ-Mag→Ⅲ-Mag, Mg、V、Zn含量及Ni/Cr值逐渐增加,Cr、Sn及REE含量逐渐降低,反映3类磁铁矿具有从岩浆成因向热液成因演化的特征。结合Ni/(Cr+Mn)-(Ti+V)、(Al+Mn)-(Ti+V)图解及磁铁矿矿相学特征,认为该矿床属于接触交代热液型铁矿床,其成矿物质来源与富碱斑岩密切相关。3类磁铁矿形成温度约300～500℃,Ⅰ-Mag→Ⅱ-Mag→Ⅲ-Mag的氧逸度有逐渐降低的趋势。地球化学特征及成矿温度、氧逸度等信息指示,腊梅铁矿床深部具斑岩型铜多金属矿床的成矿潜...     

智利卡门铁矿床磁铁矿元素地球化学特征及矿床成因意义

卡门铁矿床位于智利著名的中生代铁-铜-金成矿带内,本文根据矿石组构和矿物共生特征将卡门铁矿床成矿期次划分为硅化阶段、磁铁矿阶段、黄铜矿阶段和晚期热液脉阶段4个阶段。卡门铁矿床磁铁矿有两种类型:含硫化物块状磁铁矿、与阳起石共生磁铁矿,以含硫化物块状磁铁矿为主。电子探针研究表明,该矿床与阳起石共生磁铁矿的Fe O_T含量略高于含硫化物块状磁铁矿;整体上来看,磁铁矿的Fe O_T与Si O_2、Al_2O_3、Mg O呈负相关关系。激光剥蚀电感耦合等离子体质谱(LA-ICP-MS)微量元素成分分析表明,卡门磁铁矿轻稀土元素亏损,重稀土元素富集且分馏程度相对较大;Co、Ni元素含量高,与夕卡岩型磁铁矿较为接近,但Ni/Co比值变化较大,与夕卡岩型有明显差异,说明卡门磁铁矿与典型夕卡岩成因的磁铁矿存在一定差别,同时较高的Ni/Co比值反映了其成因与深源物质有关。卡门铁矿床磁铁矿Ti O_2-Al_2O_3-(Mg O+Mn O)三角图表明该矿床具有热液交代特征,与夕卡岩相关;(Ca+Al+Mn)-(Ti+V)成因判别图也显示该矿床有夕卡岩型铁矿特征,但同时也与IOCG型矿床有一定的相似性,这进一步证明卡门铁矿床可能并非典型的夕卡岩矿床,其成矿可能与铁氧化物铜金(IOCG)型成矿过程岩浆热液活动密切相关,这与卡门铁矿床处于智利IOCG成矿带的地质事实一致。     

磁铁矿显微结构及化学成分对铜绿山矽卡岩型铜铁矿床成矿过程的指示

铜绿山矽卡岩型铜铁多金属矿床是长江中下游鄂东南矿集区的一个典型矿床,矿体产于铜绿山岩体与三叠系碳酸盐岩地层的接触带.磁铁矿是铜绿山铜铁矿床中广泛发育的矿石矿物,选取内矽卡岩和外矽卡岩中的热液磁铁矿以及岩体中副矿物磁铁矿为研究对象,对其开展系统的显微结构观察和电子探针分析.热液磁铁矿中普遍发育有钛尖晶石出溶结构和富硅环带结构,且没有明显的后期热液交代改造现象.钛尖晶石出溶结构指示铜绿山矿床的早期热液磁铁矿具有较高的Ti含量,磁铁矿结晶后经历了降温和氧逸度降低过程导致钛尖晶石出溶.热液磁铁矿中还普遍含有较高含量的Si、Al、Cr、V、Mn、Mg、Co和Ni等元素,Si4+、Al3+、Mg2+、Mn2+等以类质同象方式进入磁铁矿晶格;但在不同产状的磁铁矿中,替代强度和机制略有不同,说明流体成分、温度、压力等物理化学条件影响元素替代强度和方式.外矽卡岩中磁铁矿的Al₂O₃/MgO比值小于4,内矽卡岩中磁铁矿的Al₂O₃/MgO比值为5~8,而副矿物磁铁矿的Al₂O₃/MgO比值约为13.岩体副矿物磁铁矿具有最高的V₂O₃含量（平均值为0.31%）,与岩体接触的内矽卡岩中的磁铁矿次之（平均值为0.14%）,外矽卡岩中磁铁矿的V₂O₃含量最低（平均值为0.01%~0.03%）.Al₂O₃/MgO比值和V₂O₃含量说明磁铁矿生长环境（熔体/热液）、围岩的成分及水-岩反应等对磁铁矿的化学组成均有影响.铜绿山矿床从岩体到内矽卡岩、再到外矽卡岩,磁铁矿的形成温度逐步下降,其成分的变化指示了磁铁矿可以作为矽卡岩矿床成矿过程的重要指示矿物.      

内蒙古赤峰市阿根他拉钠长斑岩型铁矿矿床地质特征与成因探讨

内蒙古赤峰市阿根他拉铁矿是一个可以小规模开采的铁矿与钠长石矿。铁矿所赋存的岩体为原生钠长斑岩,其可能由深部的花岗闪长岩岩浆演化而来。铁矿化可分为两个阶段,第一阶段为黑云母/绿泥石—石英—磁铁矿阶段,为本区主要的铁矿化阶段,形成网脉状—浸染状的磁铁矿矿石。该阶段成矿岩体为斑岩、网脉状矿化、伴生矿化组合与斑岩型矿床可类比及磁铁矿的(Ca+Al+Mn)—(Ti+V)图解位于斑岩型矿床中,表明该阶段具有类似于斑岩型矿床的特征。第二阶段为绿帘石—磁铁矿/赤铁矿阶段,形成可达工业品位的团块状磁铁矿/赤铁矿矿石。该阶段类似于矽卡岩型铁矿的团块状矿石,及磁铁矿的(Ca+Al+Mn)—(Ti+V)图解位于矽卡岩型铁铜矿床中,表明该阶段具有类似于矽卡岩型铁矿床的特征。将如上与钠长斑岩有关,前期表现为类似斑岩型矿床特征,后期表现为类似矽卡岩型铁矿床特征的铁矿,称为钠长斑岩型铁矿。这类铁矿应注重与绿帘石伴生的团块状铁矿的寻找。对比研究表明,钠长斑岩型铁矿明显有别于长江中下游的玢岩铁矿。     

南太行邯邢地区白涧矽卡岩型铁矿中磁铁矿与赤铁矿交代现象对矿床成因的启示

对邯邢地区白涧铁矿中磁铁矿与赤铁矿进行成因矿物学研究,精细刻画了铁的成矿过程。在岩相学观察过程中作者发现该矿床中存在2个期次的赤铁矿,其分别交代磁铁矿或被磁铁矿交代。根据磁铁矿和赤铁矿的交代关系,我们将赤铁矿划分为早、晚2个期次,并根据成矿流体的演化,将铁矿化过程划分为4个阶段。成矿流体从岩浆中分离并交代碳酸盐围岩形成矽卡岩,同时形成接触带矿(第1成矿期),随着接触带磁铁矿的形成,具有更高氧逸度的演化的流体沿着断裂带充填和交代碳酸盐地层形成早期赤铁矿(第2成矿期)。随着赤铁矿形成,氧逸度降低至磁铁矿-赤铁矿缓冲线之下,形成层间的磁铁矿(第3成矿期),SO42-转化成HS-,同时形成大量自由氧,导致成矿流体的氧逸度进一步升高,从而形成晚期赤铁矿(第4成矿期),伴随温度和氧逸度的进一步降低,成矿作用进入硫化物形成时期。整个成矿过程中氧逸度控制了成矿过程及其产物,对矽卡岩型铁矿的形成起到了主导作用。     

冀南邯邢地区白涧矽卡岩型铁矿磁铁矿成分特征与地质意义

对邯邢地区白涧铁矿矿体和岩体中磁铁矿的成分特征进行详细的成分分析,通过成因矿物学研究认为白涧铁矿矿床主要为接触交代成因,而非矿浆贯入成矿。富铁的岩浆热液在有利的断裂构造条件下充填到接触带和围岩裂隙当中,与碳酸盐围岩发生接触交代作用,形成矽卡岩型矿床。研究发现,矿区内磁铁矿以自形-半自形为主,部分有被赤铁矿、黄铁矿、黄铜矿等矿物交代的现象.围岩蚀变以矽卡岩化和钠长石化为主,具有分带性。矿体磁铁矿与岩体磁铁矿相比表现出富Mg、Mn、Si、Ca贫Fe2+、V、Cr的特征,且与典型的矿浆型磁铁矿成分差别明显。根据成因投图及单位分子中各阳离子数之间的协变图解发现,Mg、Mn与Fe2+、Si与Fe3+呈现明显的负相关,Ca与Si呈现正相关。此外,成矿过程中发生的非氧化还原反应亦可以解释矿区上方出现气孔状矿石的现象,这些成分之间的差异、相关性及发生的非氧化还原反应具有典型矽卡岩型矿床的特征。     

Police, politics, and the right to the city

Space and spatiality have recently been at the core of debates concerning the political possibilities of the city. The arguments advanced in this paper might be seen as an attempt to contribute to these debates through a reflection on the spatiality of (in) justice, politics, and the right to the city. The case of French urban policy, with its focus on distressed urban areas, and the `suburban problem' in France are used as examples to make arguments more concrete.     

Rb-Sr, K-Ar, H-and O-Isotope systematics of the Middle Riphean shales from the Debengda Formation, the Olenek Uplift, North Sibera

Clay subfractions (SFs) of <0.1, 0.1–0.2, 0.2–0.3, 0.3–0.6, 0.6–2 and 2–5 μm separated from Middle Riphean shales of the Debengda Formation are studied using the TEM, XRD, K-Ar and Rb-Sr isotopic methods. The oxygen and hydrogen isotope compositions in the SFs are studied as well. The low-temperature illite-smectite is dominant mineral in all the SFs except for the coarsest ones. The XRD, chemical and isotopic data imply that two generations of authigenic illite-smectite different in age are mixed in the SFs. The illite crystallinity index decreases in parallel with size diminishing of clay particles. As compared to coarser SFs, illite of fine-grained subfractions is enriched in Al relative to Fe and Mg, contains more K, and reveals higher K/Rb and Rb/Sr ratios. The Rb-Sr age calculated by means of the leachochron (“inner isochron”) method declines gradually from 1254-1272 Ma in the coarsest SFs to 1038-1044 Ma in finest ones, while the K-Ar age decreases simultaneously from 1225–1240 to 1080 Ma. The established positive correlation of δ¹⁸O and δD values with dimensions of clay particles in the SFs seems to be also consistent with the mixing systematics. The isotopic systematics along with data on mineral composition and morphology lead to the conclusion that mixedlayer illite-smectite was formed in the Debengda shales during two periods 1211–1272 and 1038–1080 Ma ago. The first period is likely close to the deposition time of sediments and corresponds to events of burial catagenesis, whereas the second one is correlative with the regional uplift and changes in hydrological regime during the pre-Khaipakh break in sedimentation.     

Isotopic systematics of He,Ar, S,Cu, Ni,Re, Os,Pb, U,Sm, Nd,Rb, Sr,Lu, and Hf in the rocks and ores of the Norilsk deposits

This paper reports the first results of a study of 11 isotope systems (³He/⁴He, ⁴⁰Ar/³⁶Ar, ³⁴S/³²S, ⁶⁵Cu/⁶³Cu, ⁶²Ni/⁶⁰Ni, ⁸⁷Sr/⁸⁶Sr, ¹⁴³Nd/¹⁴⁴Nd, ^206–208Pb/²⁰⁴Pb, Hf–Nd, U–Pb, and Re–Os) in the rocks and ores of the Cu–Ni–PGE deposits of the Norilsk ore district. Almost all the results were obtained at the Center of Isotopic Research of the Karpinskii All-Russia Research Institute of Geology. The use of a number of independent genetic isotopic signatures and comprehensive isotopic knowledge provided a methodic basis for the interpretation of approximately 5000 isotopic analyses of various elements. The presence of materials from two sources, crust and mantle, was detected in the composition of the rocks and ores. The contribution of the crustal source is especially significant in the paleofluids (gas–liquid microinclusions) of the ore-forming medium. Crustal solutions were probably a transport medium during ore formation. Air argon is dominant in the ores, which indicates a connection between the paleofluids and the atmosphere. This suggests intense groundwater circulation during the crystallization of ore minerals. The age of the rocks and ores of the Norilsk deposits was determined. The stage of orebody formation is restricted to a narrow age interval of 250 ± 10 Ma. An isotopic criterion was proposed for the ore-bearing potential of mafic intrusions in the Norilsk–Taimyr region. It includes several interrelated isotopic ratios of various elements: He, Ar, S, and others.     

Influences of the unsaturated,saturated, and riparian zones on the transport of nitrate near the Merced River,California, USA

Transport and transformation of nitrate was evaluated along a 1-km groundwater transect from an almond orchard to the Merced River, California, USA, within an irrigated agricultural setting. As indicated by measurements of pore-water nitrate and modeling using the root zone water quality model, about 63% of the applied nitrogen was transported through a 6.5-m unsaturated zone. Transport times from recharge locations to the edge of a riparian zone ranged from approximately 6 months to greater than 100 years. This allowed for partial denitrification in horizons having mildly reducing conditions, and essentially no denitrification in horizons with oxidizing conditions. Transport times across a 50–100-m-wide riparian zone of less than a year to over 6 years and more strongly reducing conditions resulted in greater rates of denitrification. Isotopic measurements and concentrations of excess N₂ in water were indicative of denitrification with the highest rates below the Merced River. Discharge of water and nitrate into the river was dependent on gradients driven by irrigation or river stage. The results suggest that the assimilative capacity for nitrate of the groundwater system, and particularly the riverbed, is limiting the nitrate load to the Merced River in the study area.     

扬子北缘马元铅锌矿床闪锌矿微量元素及S-Pb-He-Ar-C同位素地球化学研究

马元铅锌矿床是近年扬子陆块北缘铅锌找矿的新突破。矿体呈层状、似层状产于碑坝隆起翼部震旦系灯影组角砾状白云岩层间构造带中,围岩蚀变很弱。矿石中硫化物以闪锌矿、方铅矿为主,中粗粒晶质结构,充填于白云岩角砾间。闪锌矿富集Cd、Ge、Ag,贫In、Tl、Se,Ga/In为6~132,Ge/In多1000,成矿温度以中-低温为主。金属硫化物ε~(34)S值相对集中,为12.9‰~19.4‰,平均为17.4‰,来自于海相硫酸盐的还原。铅同位素组成稳定,~(206)Pb/~(204)Pb为17.858~17.918:~(207)Pb/~(204)Pb为15.603~15.694;~(208)Pb/~(204)Pb为37.756~38.046,具有造山带和上地壳铅的特征,震旦系可能提供了金属成矿物质。闪锌矿中流体包裹体的~3He/~4He为0.03Ra~1.05Ra,~(40)Ar/~(36)Ar为326.1~765.1,~(38)Ar/~(36)Ar为0.183~0.204,表明成矿流体主要为地壳流体和饱和大气水(大气降水或海水)的混合。闪锌矿内流体包裹体挥发分δ~(13)C_(CH_4)值为-36.01‰~-28.80‰,δ~(13)C_(C_2H_6)值为-27.72‰~-22.44‰,δ~(13)C_(CO_2)值为-23.24‰~-9.68‰,表明有机流体参与了成矿作用。石英、方解石的H-O同位素结果表明具有海水和有机水混合的特征。可见,成矿流体具有两种流体混合的特征,一为蒸发海水与围岩反应所形成的盆地卤水,二为有机流体。推测矿区可能存在一个古油气藏,由于TSR生成一高硫气藏,为区内还原性有机流体的主要来源。当富含Pb、Zn等成矿物质的成矿流体运移至富含CH_4和H_2S的还原性流体的矿区角砾岩带时,两种流体混合,Pb、Zn等遇到H_2S发生反应而沉淀成矿,并伴生热液白云石等,形成了马元铅锌矿床。综上所述,我们认为马元矿床属MVT型铅锌矿床。     

贵州岑巩羊桥罗家塘杷榔动物群的发现及其后生动物早期演化的意义

岑巩县羊桥乡罗家塘杷榔组仅出露中-上部地层,岩性单一,均为青灰、灰绿色粉砂质泥、页岩.在其上部层位发现了俞氏贵州始海百合(Guizhoueocrinus yui Zhao,Parsley et Peng,2007),计有棘皮动物始海百合、腕足动物、软体动物-软舌螺、节肢动物-三叶虫等8属9种,包括了2个未定名的新种和1...     

Breakthroughs in the biodiversity, biogeography, biostratigraphy, and basin analysis of the Beaufort group

Over the past decade researchers working on the rocks of the Beaufort Group in the main Karoo Basin of South Africa have vastly increased our understanding of this important Permo-Triassic sequence. Many new fossil forms have been discovered, allowing for breakthroughs into the biodiversity, biogeography and biostratigraphy of the group. Taxonomic and phylogenetic advances are many and varied, and cover most of the vertebrate taxa, but with emphasis placed on the temnospondyl amphibians, archosauriforms and non-mammalian synapsids, in particular the anomodontia. Biostratigraphic breakthroughs have centered on the Middle Permian Eodicynodon and Tapinocephalus assemblage zones, the Late Permian Dicynodon Assemblage Zone, and the Triassic Lystrosaurus and Cynognathus assemblage zones. Correlation of these biozones with better dated sequences in Europe, Russia and China has allowed for many chronostratigraphic refinements, which are in turn vital for sequence stratigraphical analysis of the basin fill. Based on fossil data, both the lower (Ecca–Beaufort) and upper (Beaufort–Molteno) contacts of the group have been proved to be highly diachronous. The refined chronostratigraphic framework has also allowed for a better analysis of the basin evolution through time, particularly in terms of the correlation of external stimuli that affect basin sedimentation patterns.     

Delivery of Trace Metals (Al,Fe, Mn,V, Co,Ni, Cu,Cd, Ag,Pb) from the Trinity River Watershed Towards the Ocean

The Trinity River (Texas, USA) contains in its watershed 23 different reservoir lakes, the largest one being Lake Livingston situated in the lower Trinity River watershed and two potentially polluting metroplexes, Dallas and Houston. In order to determine fluxes of nutrients and trace metals to Galveston Bay, a survey that included 24 discreet samples collected over a year and at various stages of discharge was carried out during 2000–2001. Geochemical (i.e., sorption by Fe oxyhydroxides), biological (i.e., seasonal uptake by sinking algae in Lake Livingston), and hydrological (i.e., dilution effects by increasing flow rates) controls were found to be mainly responsible for variations in dissolved trace metal concentrations rather than pollution sources. The Trinity River loads of suspended sediments and pollutant trace metals entering Galveston Bay at Anahuac were <20% of those reaching Lake Livingston, and only a few percent of the total upstream trace metal load is entering the Gulf of Mexico. Thus, during the transit through the 23 man-made lakes and an estuary, >96% of the pollutant trace metal load is lost to sediments.     

深港西部通道填海区地下水铜、钒、铊、镉、钨迁移的实验研究

填海工程使滨海地区的地下水物理化学条件改变,导致该区域地下水中重金属浓度升高。本文以深港西部通道填海区为例,采用实验室模拟填海条件的办法,初步探讨了影响填海区地下水重金属迁移的关键因素。模拟实验结果表明,填海区地下水中钨元素含量升高与地下水淡化、淤泥氧化过程以及填料风化有关;铜元素含量升高则与淤泥氧化过程以及填料风化有关;钒元素含量升高与地下水淡化和淤泥氧化过程有关,而其他元素含量升高则主要与填料风化释放有关。