High-resolution sedimentary record of lead in the coastal mud of the East China Sea in the past one hundred and fifty years

In the East China Sea （ECS）, there are some mud areas, including the south coastal mud area, the north coastal mud area, and the mud area to the southwest of Cheju Island. X-ray fluorescence （XRF） techniques and Thermal Ionization Mass Spectrometry （TIMS） were used to study the high-resolution sedimentary record of Pb concentrations and Pb stable isotopic compositions in the past one hundred and fifty years in the coastal mud of the ECS. Pb concentrations of a ^210Pb dating S5 core in the study area have increased rapidly since 1980, and reached the maximal value with 65.08 μg/g in 2000, corresponding to the fast economic development of China since the implementation of the ＂Reform and Open Policy＂ in 1978; ^206Pb/^207Pb ratios generally had stabilized at 1.195 from 1860 to 1966, and decreased gradually from 1966 to 2000, indicating that the anthropogenic source Pb contribution to the ECS has increased gradually since 1966, especially since 1980. Pb concentrations decreased distinctly from 2000 to 2003 and ^206Pb/^207Pb ratios increased from 2001 to 2003, corresponding closely to the ban of lead gasoline from 2000 in China. From 1950 to 2003, there occurred four distinct decrease events of ^206Pb/^207Pb, possibly responding to the Changjiang River （Yangtze River） catastrophic floods in 1998, 1991, 1981 and 1954; from 1860 to 1966, there were two decrease periods of ^206Pb/^207Pb, which may respond to the catastrophic floods of Changjiang River in 1931 and 1935, and 1870. As a result of the erosion and drowning by the catastrophic floods, the anthropogenic lead accumulated in soil and water environments over a long period of time was brought into the Changjiang River, then part of them was finally transported into the ECS, which leads to changes in Pb stable isotopic composition.     

Speciation of adsorbed arsenate on the surface of hydrous iron oxide

Adsorption of arsenate on hydrous iron oxide is an important process controlling geochemical cycling of arsenic in environment as well as the fate of arsenic-bearing mining wastes. The widely accepted view on the mechanism of adsorption is that arsenate is adsorbed via bidentate binuclear inner-sphere complexation. In this study, we characterized the arsenate-hydrous iron oxide sorption solids synthesized at pH=3-8 using Fourier transformed infrared spectroscopy （FTIR） and X-ray diffraction （XRD）. It has been determined that poorly crystalline ferric arsenate developed on the surface of iron oxide when arsenate was sorbed at acidic pH, while at alkaline pH the adsorption of arsenate was via bidentate complexation.     

XANES analysis of the mechanisms of arsenic removal in biological iron and manganese treatment unit

Biological iron and manganese removal utilizing indigenous iron and manganese oxidizing bacteria （IRB hereafter） in groundwater can also be applied to arsenic removal according to our pilot-scale test. The arsenic removal probably occurred through sorption and complexation of arsenic to iron and manganese oxides formed by enzymic action of IRB. We investigated the chemical properties of iron and manganese oxides in IRB floc and the valence state of arsenic sorbed to the floc to clarify the mechanisms of the arsenic [especially As （Ⅲ）] removal. The floc samples were collected from two drinking water plants using IRB （Jyoyo and Yamatokoriyama, Japan）, and our pilot - scale test site where arsenic and iron removal using IRB is under way （Mukoh, Japan）. The Jyoyo and Yamatokoriyama IRB floc samples were subjected to As （Ⅲ） and As（Ⅴ） sorption experiments. The elemental composition of the floc samples was measured. XANES spectra were collected on As, Fe and Mn K-edges at synchrotron radiation facility Spring 8 （Hyogo, Japan）. FT-IR and the X-ray diffraction spectra of the samples were also obtained. The IRB floc contained ca. 35 % Fe, 0.3%-3.5% Mn and 2%-6% P. The samples were highly amorphous and contained ferrihidrites and hydrated iron phosphate. According to XANES analyses of IRB, As associated with IRB was in ＋5 valence state when As （Ⅲ） （or As （Ⅴ）） was added in laboratory sorption test, Fe in ＋3 valence state, and Mn a mixture of＋3 and ＋4 valence states. Small shift was observed in the XANES spectra of IRB on As K-edge as the equilibration time of the sorption experiment was increased. Gradual oxidation of a small amount of As （Ⅲ） associated with IRB or change in arsenic binding with sorption site were the probable mechanism.     

Stratigraphic evolution of a fluvial–eolian succession: The example of the Upper Jurassic—Lower Cretaceous Guará and Botucatu formations, Paraná Basin, Southernmost Brazil

The Guará and Botucatu formations comprise an 80 to 120 m thick continental succession that crops out on the western portion of the Rio Grande do Sul State (Southernmost Brazil). The Guará Formation (Upper Jurassic) displays a well-defined facies shift along its outcrop belt. On its northern portion it is characterised by coarse-grained to conglomeratic sandstones with trough and planar cross-bedding, as well as low-angle lamination, which are interpreted to represent braided river deposits. Southwards these fluvial facies thin out and interfinger with fine- to medium-grained sandstones with large-scale cross-stratification and horizontal lamination, interpreted as eolian dune and eolian sand sheets deposits, respectively. The Botucatu Formation is characterised by large-scale cross-strata formed by successive climbing of eolian dunes, without interdune and/or fluvial accumulation (dry eolian system). The contact between the Guará and the Botucatu formations is delineated by a basin-wide deflation surface (supersurface). The abrupt change in the depositional conditions that took place across this supersurface suggests a major climate change, from semi-arid (Upper Jurassic) to hyper-arid (Lower Cretaceous) conditions. A rearrangement of the Paraná Basin depocenters is contemporaneous to this climate change, which seems to have changed from a more restrict accumulation area in the Guará Formation to a wider sedimentary context in the Botucatu Formation.     

Early Cretaceous U–Pb zircon ages for the Copiapó plutonic complex and implications for the IOCG mineralization at Candelaria, Atacama Region, Chile

Four of the major plutons in the vicinity of the Candelaria mine (470 Mt at 0.95% Cu, 0.22 g/t Au, 3.1 g/t Ag) and a dike–sill system exposed in the Candelaria open pit have been dated with the U–Pb zircon method. The new geochronological data indicate that dacite magmatism around 123 Ma preceded the crystallization of hornblende diorite (Khd) at 118 ± 1 Ma, quartz–monzonite porphyry (Kqm) at 116.3 ± 0.4 Ma, monzodiorite (Kmd) at 115.5 ± 0.4 Ma, and tonalite (Kt) at 110.7 ± 0.4 Ma. The new ages of the plutons are consistent with field relationships regarding the relative timing of emplacement. Plutonism temporally overlaps with the iron oxide Cu–Au mineralization (Re–Os molybdenite ages at ∼115 Ma) and silicate alteration (ages mainly from 114 to 116 and 110 to 112 Ma) in the Candelaria–Punta del Cobre district. The dated dacite porphyry and hornblende diorite intrusions preceded the ore formation. A genetic link of the metallic mineralization with the quartz–monzonite porphyry and/or the monzodiorite is likely. Both of these metaluminous, shoshonitic (high-K) intrusions could have provided energy and contributed fluids, metals, and sulfur to the hydrothermal system that caused the iron oxide Cu–Au mineralization. The age of the tonalite at 110.7 Ma falls in the same range as the late alteration at 110 to 112 Ma. Tonalite emplacement may have sustained existing or driven newly developed hydrothermal cells that caused this late alteration or modified ⁴⁰Ar/³⁹Ar and K/Ar systematic in some areas.     

鄂尔多斯盆地北部底河道砂岩型铀矿地质特征

鄂尔多斯盆地北部直罗组中的铀矿,是典型的产于河道中的砂岩铀矿,该矿床发育较好的卷状矿体。通过对该铀矿地质特征的研究,认识到发育卷状矿体的底河道砂岩型铀矿必须具备两大条件:其一是成矿砂体条件,即砂体要有较好的成层性、连通性和渗透性;其二是地层结构条件,即砂体必须存在较好的上、下隔水岩层。就砂体而言,河流相辫状沉积砂体是形成卷状矿体的主要砂体,并且以具有从辫状河向曲流河完整演化的辫状沉积砂体较好。砂体的上、下隔水岩层则有多种表现形式:下隔水层可由不透水的基岩或湖相沉积泥岩等构成;上隔水层由不透水的湖相泥岩、曲流沉积地层或岩浆岩等构成。在层间氧化作用过程上,存在纵横两个方向的氧化,即存在与河道方向一致的纵向氧化和与河道垂直的横向氧化,两种氧化作用成矿常叠加形成复杂的矿体类型;在矿化赋存的部位上,铀砂体通常发育在基底之上或不同建造之间;在古气候演变上,成矿作用发生在干旱气候条件下,或由潮湿向干旱的气候转变阶段。     

吉尔嘎朗图凹陷宝饶洼槽下白垩统层序地层与沉积体系

运用高分辨率层序地层学原理和方法,通过对钻井和地震资料的综合分析,在二连盆地吉尔嘎朗图凹陷下白垩统中识别出1个超长期基准面旋回(二级层序)SSC1和5个长期基准面旋回(三级层序):LSC1,LSC2,LSC3,LSC4,LSC5,分析了各旋回的发育特征。识别出五种类型的沉积体系:滨浅湖近岸水下扇、较深水湖浊积扇、滨浅湖扇三角洲、滨浅湖辫状河三角洲和河流沉积体系,并在等时地层格架内分析了各基准面旋回的沉积体系构成和储层砂体的发育情况。综合分析生、诸、盖条件后认为,在垂向上,LSC3旋回为本区最有利的储集层段,在平面上,本区的油气勘探应主要寻找宝饶构造带辫状河三角洲前缘砂体,主要储层砂体类型为前缘分流水道砂和前缘席状砂。     

藏南地区金和锑矿床(点)类型及其时空分布特征

本文首次对藏南地区金和锑矿床(点)地质特征、成因类型和空间分布特点进行了总结，对金和锑成矿作用与中新生代构造一岩浆活动的关系进行了论证，对区域地壳演化过程中金和锑成矿动力学机制进行了讨论。该区的金和锑矿床(点)可按容矿围岩划分为：①变质岩为主要容矿围岩矿床(点)，包括金和金一锑矿床(点)；②沉积岩为主要容矿围岩矿床(点)，包括金、锑、金一锑和锑多金属矿床(点)；③火山岩为主要容矿围岩矿床(点)，以金一银矿床为代表。根据金和锑矿床(点)空间分布特点和地质特点，将本区划分为4个矿化集中区：拉昂错一马攸木一帕羊金矿化集中区(A)，然勒金和锑矿化集中区(B)，洛扎一措美锑矿化集中区(C)和邛多江金一锑矿化集中区(D)。各矿化集中区内大多数金和锑矿床(点)与燕山晚期～喜马拉雅早期富碱火成岩具密切时空分布关系，它们是古板块对接碰撞期和碰撞期后大规模构造一岩浆活动的产物。近东西向挤压性和南北向张性断裂交汇部位以及富碱火成岩发育区是寻找金和锑矿床(点)的有利场所。     

新疆卡拉麦里金矿带成矿规律及找矿预测

新疆卡拉麦里成矿带内地层较全、构造发育、岩浆活动频繁，志留系、泥盆系和石炭系在带内广泛发育，为本区主要含金地层．卡拉麦里深断裂严格控制区内侵入岩、次一级构造和矿产分布，构成岩浆侵入的主要通道，与此有关的次一级断层和裂隙则构成良好的赋存空间．卡拉麦里深大断裂纵贯全区，金成矿地质条件优越，沿走向Au异常、金矿床(点)成群成带分布，最后确定了7个金找矿远景区．     

滇西龙川江盆地铀矿化特征

龙川江盆地是滇西主要的铀矿赋矿盆地之一,现已探明一批砂岩型铀矿床。本文根据野外地质调查及室内系列编图,运用水成铀矿成矿理论,对龙川江盆地的基本特征及铀矿化特征进行了讨论,认为铀矿床主要分布于西部斜坡带,赋存于冲积扇沉积体系砂体中,且与潜水层间氧化带关系密切。