内蒙古乌兰沟埃达克岩锆石U-Pb年龄及构造环境

内蒙古中部贺根山缝合带的梅劳特乌拉蛇绿岩中,新发现乌兰沟埃达克岩,岩性为花岗闪长岩。LA-ICP-MS锆石UPb测年结果表明,乌兰沟埃达克岩的侵位年龄为279.3±1.4Ma,其形成时代为早二叠世。乌兰沟埃达克岩SiO_2含量为65.92%~69.65%,MgO为1.34%~2.16%,Al_2O_3为15.30%~17.33%,Na_2O/K_2O值为3.95~14.09,Sr=359.60×10~(-6)~734.00×10~(-6),Yb=0.83×10~(-6)~2.02×10~(-6),Y=6.65×10~(-6)~12.84×10~(-6);富集K、Rb、Sr等大离子亲石元素,亏损Nb、Ta、Ti、P等高场强元素;稀土元素总量为32.18×10~(-6)~65.41×10~(-6),明显较低,轻、重稀土元素分馏明显,(La/Yb)N值为2.84~7.56,无明显Eu异常,显示出高硅埃达克岩(HSA)的地球化学特征。该埃达克岩具有岛弧型岩浆岩特征,形成于俯冲带岛弧环境,可能为洋内俯冲洋壳+俯冲深积物部分熔融并与上覆地幔楔橄榄岩反应成因。根据乌兰沟埃达克岩与梅劳特乌拉蛇绿岩的时空分布与演化特征,贺根山缝合带在早二叠世可能存在洋内俯冲作用。     

内蒙古梅劳特乌拉蛇绿岩中早二叠世埃达克岩与古亚洲洋东段洋内俯冲

贺根山缝合带东部晚石炭世梅劳特乌拉SSZ型蛇绿岩中的埃达克岩,岩性为安山岩和英安岩。LA-ICP-MS锆石U-Pb定年结果显示,埃达克岩的形成时间为294.1±2.2 Ma,时代为早二叠世。地球化学特征显示,该埃达克岩属于低钾拉斑系列和中钾钙碱性岩石,具有高硅(Si O_2=64.12%～69.12%)、高铝(Al_2O_3=16.05%～18.59%)、富钠贫钾(Na_2O=5.08%～6.80%,K_2O=0.70%～1.22%,Na_2O/K_2O=4.50～7.26)、高Sr (291.22×10~(-6)～762.20×10~(-6)),低Yb (0.74×10~(-6)～1.28×10~(-6))、低Y(7.33×10~(-6)～12.74×10~(-6))等特征。相对富集大离子亲石元素(如K、Rb和Sr),亏损高场强元素(如Nb、Ta、Zr、Ti和P),稀土元素总量较低(40.97×10~(-6)～108.69×10~(-6)),贫重稀土元素,无明显的负Eu异常,为典型的埃达克岩。梅劳特乌拉埃达克岩形成于俯冲带岛弧环境,可能为俯冲洋壳部分熔融而形成的埃达克质熔体,经俯冲带上升过程中与地幔楔橄榄岩发生相互作用而形成。埃达克岩和梅劳特乌拉蛇绿岩(308 Ma)的蛇纹石化方辉橄榄岩、层状-块状辉长岩、枕状拉斑玄武岩、玻安岩、富Nb玄武岩和高镁安山岩等构成洋内初始俯冲作用形成的较丰富且完整的岩石组合序列。研究结果表明,晚石炭世—早二叠世古亚洲洋东段开启了洋内初始俯冲作用。     

甘肃北山牛圈子地区志留纪骆驼圈西岩体的岩石成因及构造意义

北山牛圈子地区的骆驼圈西埃达克岩为过铝质钙碱性岩浆系列,具有高的SiO_2(57.94%)、Al_2O_3(16.66%)和低的MgO(4.32%)含量,较高的Na_2O/K_2O比值(3.13),显示富钠的特征;而在微量元素上,高Sr(589×10~(-6)~1170×10~(-6)),低Y(4.60×10~(-6)~13.90×10~(-6))和Yb(0.43×10~(-6)~1.32×10~(-6));轻重稀土分异明显(La/Dy)N=4.60~13.87、(La/Yb)N=7.17~20.58,Eu异常不明显(Eu/Eu*=0.85~1.32);富集轻稀土和大离子亲石元素,而亏损高场强元素Nb,Ta,Ti和重稀土HREE,与世界上典型的俯冲洋壳熔融形成的埃达克岩特征相似。结合区域上埃达克岩的研究成果和岀露的构造位置,以及与牛圈子蛇绿岩的关系,认为骆驼圈西埃达克岩是志留纪(U-Pb年龄为428.9 Ma)时期热的洋壳向公婆泉—东七一山早古生代活动陆缘带俯冲过程中部分熔融的产物。对该岩体的研究,为进一步研究北山造山带早古生代北山洋盆闭合和晚古生代北山洋盆重新裂开提供新的依据。     

北祁连山东段银硐粱早古生代高镁埃达克岩：地球动力学及成矿意义

银硐粱早古生代花岗闪长岩分布在北祁连造山带东段屈吴山地区,侵入于原阴沟群和前寒武纪变质岩系中。它与米家山、扁强沟、清凹山以及南华山花岗岩类共同构成长约220千米的构造—花岗岩带,沿 NW-NWW 向展布。地球化学研究结果表明,银硐粱花岗闪长岩具有典型的高镁埃达克岩的地球化学特征,它们具有富 Na 贫 K,SiO_2>56%,Al_2O_3>15%,Na_2O>4.0%(4.51%～4.92%),K_2O(1.96～2.77%),Na_2O/K_2O=1.63～2.40,属钙碱性侵入岩;高 Sr(599～691×10~(-6)),低 Y(6.3～8.1×10~(-6)),Sr/Y>40(81～94),Y/Yb>10(Yb<1.9×10~(-6)),La/Yh>20(22～45)以及相对于典型的埃达克岩,具有更高的 Mg~#(58～64,平均59)和相容元素 Ni(31～38×10~(-6))和 Cr(35～43×10~(-6))含量;富集轻稀土元素(LREE),亏损重稀土元素(HREE),(La/Yb)_N>10(16～32),轻微负 Eu 异常(Eu/Eu*平均为0.94),∑REE(85～112)×10~(-6);微量元素蛛网图显示,岩石富集大离子亲石元素(Rb、Ba、Sr),Nb-Ta 和 Ti 负异常,相对于 Ce 和 Nd,Sr 为正异常。由于银硐粱高镁埃达克岩是俯冲洋壳部分熔融的产物,因此,它的存在表明,老虎山弧后洋盆在早古生代早期发生了向北的俯冲作用。银硐粱 Cu-Au 成矿作用与高镁埃达克岩关系密切,表明在北祁连构造带东段寻找与埃达克岩有关的 Cu-Au 矿床是一个新的找矿思路。     

内蒙古梅劳特乌拉蛇绿岩中埃达克岩的发现及其演化模式

本文报道在内蒙古西乌旗梅劳特乌拉SSZ型蛇绿岩中新发现的早二叠世洋内弧呼和德埃达克岩。该埃达克岩位于贺根山缝合带内,侵位于晚石炭世梅劳特乌拉SSZ型蛇绿岩带之中,岩性为细粒-中粒花岗闪长岩。锆石LA-ICP-MS U-Pb测年表明,呼和德埃达克岩的侵位年龄为294.7±1.7Ma,其形成时代为早二叠世。呼和德埃达克岩属于低钾拉斑系列与中钾钙碱性系列的过渡型岩石,SiO_2为64.93%~69.50%,MgO为0.80%~1.48%,Al_2O_3为15.72%~19.11%,Na2O/K2O为3.01~8.60;Sr为368×10~(-6)~700.40×10~(-6),Yb为0.95×10~(-6)~1.76×10~(-6),Y为5.26×10~(-6)~9.27×10~(-6);相对富集大离子亲石元素(LILE)K、Rb和Sr等,亏损高场强元素(HFSE)Nb、Ta、Zr、Ti和P等;稀土元素总量较低(32.68×10~(-6)~66.69×10~(-6)),轻重稀土分馏明显,(La/Yb)N为3.31~5.10,无明显的Eu负异常,显示了典型埃达克岩的地球化学特征。呼和德埃达克岩与梅劳特乌拉SSZ型蛇绿岩,构成梅劳特洋内弧初始俯冲作用较为完整连续的蛇纹石化方辉橄榄岩、层状-块状辉长岩、枕状拉斑玄武岩、玻安岩、富Nb玄武岩和高镁或镁安山岩等岩石组合序列。岩石学和地球化学特征表明,呼和德埃达克岩形成于洋内弧环境,为洋内弧初始俯冲作用早期的深成岩。这标志着古亚洲洋贺根山缝合带洋壳初始俯冲发生于早二叠世。根据晚石炭世-早二叠世梅劳特乌拉洋内弧的主要特征和识别标志,初步建立了晚石炭世-早二叠世梅劳特乌拉洋内弧初始俯冲系统形成演化模式。     

昌宁-孟连结合带牛井山早古生代埃达克岩锆石U-Pb年龄、岩石成因及其地质意义

昌宁-孟连结合带是西南三江地区重要的古特提斯结合带,本文报道该带牛井山蛇绿混杂岩带内的早古生代英云闪长岩的锆石U-Pb年龄和Hf同位素、全岩地球化学特征,探讨其岩石成因,揭示早古生代(原)特提斯演化过程和恢复古地理格局。利用LA-ICP-MS对英云闪长岩进行锆石U-Pb定年,获得~(206)Pb/~(238)U加权平均年龄为468±2Ma(MSWD=1.4,n=22),代表岩浆岩结晶时代。对锆石进行原位微区Hf同位素分析获得锆石ε_(Hf)(t)=+1.6~+2.8。牛井山英云闪长岩具有高的SiO_2(61.6%~67.16%),Al_2O_3(15.4%~17.64%),Na_2O(2.93%~3.25%)含量,高的Na_2O/K_2O(3.9~5.4)比值。微量元素具有高Sr(469×10~(-6)~533×10~(-6)),低Yb(0.66×10~(-6)~1.22×10~(-6))和Y(8.5×10~(-6)~16.3×10~(-6)),Eu正异常(1.01~1.37)的特征。此外,在同等SiO 2条件下,还具有相对高的Mg~#和MgO(Mg~#=50~51,MgO=2.84%~3.58%)。这些特征表明英云闪长岩具有高镁埃达克岩的性质。岩石成因研究表明牛井山高镁埃达克岩很可能是俯冲洋壳加上部分大洋沉积物部分熔融并与上覆地幔橄榄岩反应的产物。早古生代洋壳俯冲成因的埃达克岩的发现证明昌宁-孟连特提斯洋演化历史可追溯至约468Ma。昌宁-孟连结合带早古生代岩浆作用与龙木错-双湖结合带早古生代洋壳残片的时代一致、构造属性相似,我们认为昌宁-孟连结合带与木错-双湖结合带可对比,它们代表了一个统一的古生代特提斯大洋残余。     

阿尼玛卿蛇绿岩带花岗—英云闪长岩锆石U—Pb同位素定年及大地构造意义

对阿尼玛卿蛇绿岩带布青山段花岗—英云闪长岩进行的锆石U—Pb同位素定年及岩石化学研究表明,该岩体锆石U—Pb年龄为402±24Ma,归属加里东末期,并非二叠-三叠纪同造山岩浆活动的产物;岩石属钙碱系列,具岛弧花岗岩特征,暗示着本区在早古生代发生过洋壳俯冲及岛弧岩浆活动事件,并为本区早古生代蛇绿岩的存在提供了佐证。     

内蒙古查干拜兴晚石炭世埃达克岩的成因及其洋内俯冲作用的约束

由于缺少可靠的埃达克岩石的发现和系统研究,内蒙古索伦地区有无洋内初始弧火成岩组合和洋内俯冲作用尚不清楚,制约了古亚洲洋东段古生代古大洋俯冲消亡过程的进一步认识.本文报道在内蒙古苏尼特右旗蛇绿混杂岩带中新发现的晚石炭世埃达克岩,岩性为英云闪长岩.锆石LA-ICP-MS U-Pb定年显示,查干拜兴埃达克岩的形成时间为322.3±5.2 Ma,时代为晚石炭世.该埃达克岩属于低钾拉斑系列-中钾钙碱性系列岩石,SiO2含量为65.57％～67.89％,Al2O3为15.48％～16.55％,MgO为0.76％～1.63％,Na2O/K2O为2.39～18.09,Sr为371×10-6～486×10-6,Yb为0.60×10-6～1.76×10-6,Y为4.87×10-6～7.82×10-6.相对富集大离子亲石元素K、Rb和Sr等,亏损高场强元素Nb、Ta、Zr、Ti和P,稀土元素总量(∑REE)较低(22.83×10-6～80.63×10-6),贫重稀土元素,无明显的Eu异常,显示了典型埃达克岩的地球化学特征.查干拜兴埃达克岩具有岛弧型岩浆岩特征,形成于俯冲带岛弧环境,可能为俯冲洋壳部分熔融而形成的埃达克质熔体,经俯冲带上升过程中与地幔楔橄榄岩发生相互作用而形成.根据查干拜兴埃达克岩与区域石炭纪蛇绿岩的时空分布与演化特征,表明古亚洲洋东段索伦缝合带在晚石炭世存在洋内俯冲作用.     

大兴安岭南段东麓中生代O型埃达克质火山岩及其成因、古构造环境和找矿意义

蒙东西拉禾伦河北侧查干木伦河流域,属中生代大兴安岭火山-侵入杂岩带南段。最近区内晚侏罗世满克头鄂博组陆相火山杂岩火山盾中,发现有埃达克质火山岩,与少量钠质流纹岩和玄武岩共生。埃达克岩 Al_2O_3>15%,MgO<3.4%,K_2O 平均=1.77%,Na_2O/K_2O>1,LREE 富集,HREE 及 LIRE 强烈亏损,无负铕异常,高 Sr(497.91～896.40×10~(-6)),低 Y(4.33～15.77<18×10~(-6)),低 Yb(0.35～1.54<1.9×10~(-6)),I_(Sr)=0.70374～0.70594,ε_(Nd)(t)为-0.45～ 6.58,在 K-Na-Ca、Rb-Sr-Ba、Sr/Y-Y 和 Sr/Yb-Yb 等图中属埃达克岩,具奥长花岗岩演化趋势,是典型的 O 型埃达克岩。其与共生岩石ε_(Nd)(t)、I_(Sr)与晚古生代玄武岩的接近,部分岩石 t_(DM)(677～845Ma)与晚古生代俯冲洋壳(t_(DM)=627～998Ma)相同,Sr-Nd 同位素及Zr/Hf-Nb/Ta 比值具有亏损地幔与下地壳混合特征,另有岩石(t_(DM)=343～453Ma)源于古生代年轻地幔。据此推论其源岩是以晚元古代俯冲洋壳为主,多源物质混合的增生地体下地壳。La_N/Yb_N-Yb_N 及 La/Sm-La 图证明埃达质岩浆是榴辉岩化源岩部分熔融的原始岩浆,钠质流纹岩是该原始岩浆分离结晶产物,玄武岩浆则可能是源岩深度熔融的结果。岩石成分及微量元素判别该火山活动环境是大陆边缘弧。大兴安岭地区在中生代出现埃达克质火山岩及该类火山弧,未必与环太平洋或者鄂霍茨克海俯冲构造直接相关,而是晚古生代古亚洲洋残存洋壳在中生代沿续存俯冲断裂继续向增生地体下地壳俯冲并发生部分熔融结果。区内与满克头鄂博组有关的铁、铜、金矿化,应有大矿前景。     

新疆东准噶尔早志留世埃达克岩——来自锆石U-Pb年龄、地球化学及Sr-Nd-Hf同位素的证据

新疆东准噶尔野马泉地区索尔巴斯塔乌石英闪长岩锆石U-Pb年龄为442.5±5.6 Ma。该岩体SiO_2为63.75%~65.40%,Al_2O_3为17.07%~18.00%,Na_2O/K_2O比值为5.28~6.82,MgO为1.11%~1.35%;富集大离子亲石元素(LILE,如K、Rb、Ba和Sr),而亏损高场强元素(HFSE,如Ta、Nb、Zr和Ti)及P,Sr为783×10~(-6)~1 030×10~(-6),Y为8.10×10~(-6)~10.80×10~(-6),Yb为0.84×10~(-6)~1.04×10~(-6),Sr/Y比值为82.59~112.32,具埃达克岩的典型特征;具有相对低的(~(87)Sr/~(86)Sr)i值(0.703 77~0.704 04)和相对高的εNd(t)值(+6.9~+7.2),且锆石具有相对高的εHf(t)值(+10.7~+13.7),暗示岩浆很可能起源于亏损的年轻地幔源区,与俯冲洋壳熔融形成的埃达克岩相似。结合区域地质背景,认为索尔巴斯塔乌石英闪长岩是由俯冲的大洋板片边缘受到来自板片窗高温软流圈地幔物质的烘烤发生部分熔融形成的,为阿尔曼泰蛇绿岩代表的古亚洲洋于早志留世向南俯冲消减过程中形成的岩浆弧记录。     

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.     

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。     

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.     

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.     

海南长塘岭矿区大坡岩体岩石学、地球化学特征及其含矿性初探

海南大坡岩体位于五指山褶皱带内,主要受昌江—琼海构造带、琼西构造带与潭爷断陷构造带控制.岩石地球化学及岩石学研究表明,大坡岩体形成于海西-印支晚期,岩性单一,主要为中细粒似斑状黑云母二长花岗岩.岩体显示为Ⅰ型花岗岩与S型花岗岩的混合,主体以地壳物质部分熔融为主,形成过程有少量地幔物质加入.元素对的比值及稀土元素配分特征说明岩体钨锡等多金属含矿性可能较差.     

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.