甘肃北山地区骆驼山镁铁--超镁铁岩体岩石成因

骆驼山镁铁--超镁铁岩体主要岩石类型有单辉橄长岩、橄榄辉长苏长岩、橄长岩、辉长苏长岩、辉长岩。橄榄石Fo为76~83,为贵橄榄石。辉石化学特征以及主量元素特征表明其属拉斑玄武岩系列,稀土元素配分曲线总体表现为轻稀土稍富集、重稀土微分异的特征。微量元素具有大离子亲石元素(Rb、Ba、Sr)相对富集,高场强元素Ta、Hf、Th相对亏损的特征。岩浆演化过程中分离结晶作用主要受单斜辉石控制。Nb/U、Ce/Pb值更接近于地壳值以及敏感元素比值协变关系表明岩浆演化过程发生了同化混染作用。Th/Yb-Nb/Yb、La/Ba-La/Nb之间的关系指示岩浆源区可能为流体交代改造的富集型岩石圈地幔。     

新疆东天山黑白山镁铁超镁铁岩地球化学、U-Pb年代学、Hf同位素特征及地质意义

黑白山镁铁超镁铁岩位于新疆中天山地块与觉罗塔格构造带的分界断裂——阿其克库都克大断裂南侧约4 km处。该岩体主要由阳起石化橄榄辉石岩、辉橄岩、辉石岩、蚀变细粒辉长岩组成,对岩体的主微量及稀土元素地球化学特征研究表明,岩体属铁质镁铁超镁铁岩,具低钾拉斑玄武质岩的分异特征;岩石具相对较低SiO₂(43.90%~52.80%)、相对富Na₂O(0.38%~2.97%),贫K₂O(0.11%~0.47%)及Na₂O>K₂O特征;MgO值变化大且较高(4.25%~32.49%),较高Mg#(63.94~82.98),相对富集轻稀土((La/Yb)N为2.03~5.76),富集大离子亲石元素Rb,Ba,U,La,亏损高场强元素Nb,Ta,Ce,Ti,强烈富集Pb,说明岩石具幔源特征和岛弧岩浆特征。LA-ICP-MS锆石UPb年龄(392.7±4.5)Ma表明,该岩体属早泥盆世岩浆活动的产物。Hf同位素等地球化学特征和岩相学显示,岩浆起源于含有早期俯冲洋壳的亏损软流圈地幔,在岩浆演化过程中受到地壳及围岩混染,但混染作用较弱。黑白山岩体的发现为北天山洋在早古生代沿阿其克库都克断裂向南俯冲提供了新的证据。     

新疆东昆仑达拉库岸镁铁-超镁铁质岩体年代学、地球化学及成矿条件

达拉库岸镁铁-超镁铁质岩体位于东昆仑造山带南带之喀拉米兰晚古生代沟弧系,主要由二辉橄榄岩、单辉橄榄岩、橄榄二辉岩、单辉辉石岩和辉长岩组成。辉长岩的锆石U-Pb谐和年龄为244.4±1.5Ma,属于中三叠世。岩石普遍弱富集稀土元素和大离子亲石元素(Rb、Ba、Sr),亏损不相容元素(Nb、Ta)。岩体原生岩浆为高镁拉斑玄武质岩浆(Mg O 11.4%,Fe O10.8%)。元素地球化学和Nd、Sr同位素组成特征表明岩浆源区为富集岩石圈地幔,岩浆运移和侵位过程中遭受不同程度地壳物质的同化混染作用。依据橄榄石组分模拟获得橄榄石结晶过程中母岩浆达到硫饱和,并发生硫化物的熔离作用。从岩体特征、矿石结构、原生岩浆性质、深部硫化物熔离和物探信息等方面综合分析,岩体具有形成岩浆型铜镍硫化物矿床的良好条件。     

新疆且末县几克里阔勒镁铁—超镁铁岩体 地球化学特征及岩石成因

新疆且末县几克里阔勒镁铁—超镁铁岩体位于塔里木板块南缘活动带之喀拉米兰晚古生代沟弧系中段北侧,侵入下石炭统满达拉恰普组第三段海相碎屑岩、碳酸盐岩及中酸性火山岩建造中。主要岩石类型有纯橄岩、二辉橄榄岩、单辉橄榄岩、含长橄榄二辉岩、二辉岩、橄榄辉长岩、淡色辉长岩。岩石地球化学及岩相学特征表明:岩浆作用早期,分离结晶作用主导了岩浆演化过程和岩体形成过程,橄榄石和斜方辉石呈分离/堆晶相;矿物结晶顺序是:尖晶石/橄榄石→斜方辉石→单斜辉石→单斜辉石+斜长石→褐色普通角闪石/黑云母。原生岩浆可能来自原始地幔或中等程度熔融的高镁玄武质岩浆,属拉斑玄武岩系列,形成过程中受到了一定程度同化混染作用的影响,但硫化物熔离程度较弱。岩浆源区位于尖晶石稳定域。     

新疆东昆仑达拉库岸镁铁-超镁铁岩的矿物化学及其属性

达拉库岸镁铁-超镁铁岩位于东昆仑造山带南带之喀拉米兰晚古生代沟弧系,由二辉橄榄岩、单辉橄榄岩、橄榄辉石岩、单辉岩、含长辉石岩和辉长岩组成。单辉橄榄岩和橄榄辉石岩中橄榄石均为贵橄榄石(Fo=84.55~89.08),其MnO含量为0.13%~0.29%,NiO含量为0.09%~0.28%;单斜辉石为透辉石和普通辉石,其MgO含量为15.12%~16.98%,Fe O含量为3.84%~5.34%,CaO含量为21.10%~22.95%;与蛇绿岩套中的同类岩石的橄榄石和单斜辉石成分存在较大差异,与夏日哈木和金川镁铁-超镁铁岩中同类岩石的矿物成分类似,表明达拉库岸岩体不是蛇绿岩套的组成部分,而是陆壳中的侵入体。单斜辉石成分表明其母岩浆为拉斑玄武质岩浆,可能形成于与俯冲有关的大陆边缘裂谷环境。达拉库岸岩体具有形成岩浆型铜镍硫化物矿床的条件。     

中天山白石泉镁铁-超镁铁质岩体岩石学与矿物学研究

白石泉地区镁铁一超镁铁质岩体处于塔里木板块前缘活动带与中天山地块接合部位，是中天山地块华力西中期岩浆活动的产物。主要岩石类型有辉石橄榄岩（斜方辉石橄榄岩、斜长二辉橄榄岩）、橄榄辉石岩、橄长岩、辉长岩及角闪辉长岩等，主要造岩矿物为橄榄石、斜方辉石、单斜辉石、角闪石、斜长石及黑云母。橄榄石均为贵橄榄石，其Fo值（78-85）位于含铜镍硫化物矿橄榄石的Fo值范围之内；辉石主要有顽火辉石、古铜辉石、紫苏辉石、透辉石等；斜长石的环带构造较为发育；角闪石的FeO含量随着岩浆的演化逐渐增加。它们与造山带环境中的东疆型镁铁一超镁铁杂岩中的造岩矿物具有相同的特征。这些特征表明了白石泉地区的镁铁一超镁铁质岩体的原始岩浆为高镁的拉斑玄武质岩浆。     

青海省乌兰地区肯得隆富钛铁矿镁铁-超镁铁质岩体的岩石与矿石成因

肯得隆镁铁-超镁铁质岩体位于青海柴达木盆地北缘欧龙布鲁克微陆块中。岩体为半隐伏岩体,地表零星出露。岩体岩石类型丰富,有蛇纹岩、单辉橄榄岩、二辉橄榄岩、橄榄二辉岩、橄榄单辉岩、橄榄苏长辉长岩、橄榄角闪辉长岩、角闪辉长岩、蚀变辉长岩、斜长岩。辉长岩、辉石岩中见稀疏浸染状、星点浸染状钛铁矿。钛铁矿含量以5%~10%为主,个别含量可达10%~20%,具海绵陨铁结构,属岩浆晚期矿化作用产物。岩体中辉长岩锆石U-Pb年龄为491±3Ma(MSWD=0.7)。岩体岩石的化学组成属于拉斑玄武质系列,各岩性岩石的稀土元素配分形式基本一致,均呈轻稀土富集的右倾型。微量元素特征表现为富集大离子亲石元素(Cs、Rb、Ba、Th、U),亏损高场强元素(Nb、Ta、Ti、P)。岩体(87Sr/86Sr)i值为0.704731~0.710280,εNd(t)=-4.49~+0.83。岩浆在冷凝过程中发生了橄榄石-单斜辉石-斜方辉石-斜长石-普通角闪石的分离结晶作用。岩石地球化学特征表明岩体受到同化混染作用。肯得隆岩体的原生岩浆为普通的玄武质岩浆,源自被古生代俯冲熔/流体交代的富集岩石圈地幔。钛铁矿的富集机制是:岩浆在氧逸度低于NNO条件下经历了相对高度的分异演化而最终达到钛铁矿富集。     

东昆仑石头坑德镁铁-超镁铁质岩体矿物学特征及成矿指示

石头坑德镁铁-超镁铁质岩体位于东昆仑造山带东段五龙沟地区,邻近昆中大断裂,主要岩性为辉石岩、橄辉岩、橄榄岩、辉长岩等,铜镍矿体主要赋存于Ⅰ号岩体的辉石岩、橄辉岩和橄榄岩中。岩石地球化学特征表明,其镁铁比值(m/f)变化范围在2.77~6.01之间,属铁质系列的镁铁-超镁铁岩,有利于成铜镍矿。稀土总量总体较低,轻稀土元素之间分馏强,重稀土元素之间分馏弱。岩石总体富集LILE(Rb、Ba、Th、U),贫HFSE(Nb、Ta、Zr、Y),具有明显的Rb、U正异常及Nb、Ta的负异常。超镁铁岩类橄榄石中的Ni普遍亏损,指示深部存在硫化物的熔离作用,在橄榄石结晶之前,大量的Ni进入到硫化物中,极有利于形成富矿岩浆或矿浆。可见,伴随同化混染作用的发生,岩浆中S达到过饱和,进而硫化物发生不混溶作用,富含硫化物的岩浆运移至东昆仑造山带邻近昆中断裂构造薄弱的部位成岩成矿。铜镍矿体多赋存在含橄榄石的超镁铁质岩体内,指示石头坑德岩体深部存在高度富集铜镍的部位,是下一步的找矿方向。     

新疆库鲁克塔格地区兴地Ⅱ号镁铁-超镁铁质岩体的地球化学特征与岩石成因

兴地Ⅱ号镁铁-超镁铁质岩体位于塔里木盆地东北缘的库鲁克塔格地区,形态为不规则的漏斗状岩盆,出露面积约10km²。岩石类型主要有方辉橄榄岩、二辉橄榄岩、(含长)单辉橄榄岩、橄榄辉石岩、方辉辉石岩、二辉辉石岩、单辉辉石岩、橄榄辉长苏长岩、辉长苏长岩、橄榄辉长岩、辉长岩等,岩石类型属拉斑玄武岩系列。岩体的稀土元素含量低(∑REE=10.73×10^-6~77.44×10^-6),富集轻稀土元素(La/Yb)_N=4.06~7.73和大离子亲石元素(Cs、Rb、Sr、Ba),亏损高场强元素尤其是Nb、Ta、Ti、P等,δEu为0.90~2.46多数岩石显示出正铕异常。岩相学及地球化学特征表明,岩浆运移过程中主要发生了橄榄石、斜方辉石、单斜辉石的分离结晶作用以及斜长石的聚集/堆晶。原生岩浆为富镁拉斑玄武岩,岩浆源区为富集型岩石圈地幔,岩浆上升侵位过程中局部遭受了陆壳的同化混染。兴地Ⅱ号岩体与金川岩体具有很多的相似之处,而且兴地Ⅱ号岩体已见有铜镍矿化。因此,兴地Ⅱ号岩体具有很好的找矿前景。     

东天山黄山南镁铁-超镁铁岩体的岩浆演化过程:矿物学、Sr-Nd同位素特征的指示

黄山南镁铁-超镁铁质岩体位于东天山造山带觉罗塔格构造带内,属于土墩-黄山-图拉尔根镁铁-超镁铁质岩带。本文在前人研究的基础上,从橄榄石、辉石矿物学组成和全岩Sr、Nd同位素等方面对黄山南岩体进行了分析研究,并与黄山、黄山东、香山等典型含矿岩体作了对比,旨在进一步查明黄山南岩体的岩浆源区和母岩浆性质及其岩浆演化过程。Sr-Nd同位素特征表明黄山南岩体来自一个弱亏损的地幔源区,相较黄山、黄山东、香山等岩体的源区具有更加富集的特征。黄山南岩体中的橄榄石属于贵橄榄石,斜方辉石主要为古铜辉石,少数为紫苏辉石,单斜辉石主要为顽透辉石、普通辉石和少数的透辉石。单斜辉石和橄榄石的成分特征表明形成黄山南岩体的母岩浆为演化程度较低的拉斑玄武质岩浆,且母岩浆成分具有高Mg、高Ni的特点。计算得到黄山南岩体母岩浆的Fe O~T=13.20%、MgO=16.96%、Ni=377.2×10~(-6),且母岩浆在结晶分异过程中没有经历充分的硫化物熔离作用,这也是造成母岩浆中Ni含量较高以及岩体含矿性较差的主要因素。     

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.