云南个旧大白岩铜锡矿床铜锡与共伴生组分赋存状态研究

位于个旧市南部的卡房矿田大白岩铜锡矿是个旧地区重要的铜矿产出地段,共伴生锡、金、银、钨、铋等有益组分。通过光薄片鉴定、电子探针测试和人工重砂分析发现,大白岩铜锡矿铜主要赋存状态为黄铜矿,其次为银黝铜矿和黝锡矿;锡主要以锡石,黝锡矿形式存在;伴生组分钨主要为白钨矿,铋元素以辉铋矿和自然铋存在,硫主要为磁黄铁矿、黄铁矿,其次为黄铜矿等硫化物,磁黄铁矿和黄铜矿中含有微量金。     

辽西义县晚白垩世大兴庄组流纹岩的地球化学特征及其成因

辽西义县晚白垩世大兴庄组流纹岩具有埃达克质火山岩的特征.这些流纹岩SiO₂≥68.62%、Al₂O₃≥14.40%、MgO < 1.2%(Mg# < 0.45)、Sr＞360μg/g、Yb < 1.1μg/g、Y < 12μg/g、La/Yb＞40、Sr/Y≥39和Nb/Ta＞17.5;轻稀土元素富集, 重稀土元素和高场强元素(如Nb、Ta、Ti)明显亏损, 轻重稀土元素强烈分馏, 具有弱的负铕异常; Nd、Sr同位素具有较低的143Nd/144Nd(0.511376~0.511441, ε_Nd(t)=-23.45~-22.16)和适中的87Sr/86Sr(0.7073~0.7074, ε_Sr(t)=32.38~32.8)比值, 具有富集地幔端员(EMI)特点.这些特征表明, 大兴庄组流纹质岩浆起源于较厚下地壳榴辉岩部分融熔, 也说明中生代晚期局部仍残留较厚的下地壳, 这为进一步理解燕山造山带中生代到新生代岩石圈减薄提供了重要信息.      

内蒙古胜利煤田共生锗矿的成因地球化学初探

用统计和作图的分析方法,对内蒙古胜利煤田中共生锗矿床的锗品位与挥发分、灰分、硫分的关系进行了研究。结果表明煤中锗品位与挥发分呈正相关、与原煤灰分负相关、与洗煤灰分正相关关系;全区煤属中硫煤,锗品位与原煤和洗煤硫分均呈正相关关系,煤的灰分指数较低(3 579);锗分布不均匀,富锗煤矿明显属于断裂坳陷边缘沉积,锗品位可以在煤层的顶部、中部、底部同时或单个部位呈现高值,大多数煤层中部出现锗高品位值,这有别于以往所报道的锗品位只在煤层顶、底部相对富集的研究结论。认为胜利煤田锗主要与有机质结合;锗的有利聚集条件是水动力较弱、地下水位较低、强还原的停滞沼泽环境;泥炭聚集阶段有机质的吸附作用是锗的主要富集机制。     

蒙古国东南部巴音苏赫图晚古生代—早中生代二长花岗岩地球化学特征及其对构造环境的约束

巴音苏赫图二长花岗岩位于西伯利亚板块东南缘陆缘增生带与二连—贺根山板块对接带北缘之间。该岩体由石炭纪及三叠—侏罗纪两期花岗岩组成,均以高硅、富Al2O3、K2O、Na2O,贫MgO、CaO为特征。微量元素表现为富集LILE、亏损HFSE。弱富集LREE,Eu负异常明显。岩石学和地球化学综合研究表明:两期花岗岩早期为高钾钙碱性、准铝质-过铝质花岗岩碰撞期I型花岗岩,晚期花岗岩具有A型花岗岩特点。Sr-Nd同位素研究表明:石炭纪二长花岗岩(87Sr/86Sr)i比值较低(0.700 62～0.704 82),εNd(t)为正值(0.9～1.5),岩浆来自于增生的岛弧或年轻的幔源物质,在岩浆上升过程中遭受了少量地壳物质的混染;晚三叠世—早侏罗世花岗岩(87Sr/86Sr)i比值较高(0.709 96～0.710 19),εNd(t)较低,为-0.3～0.3,该期次花岗岩与晚石炭世花岗岩同源,受地壳混染程度相对较高。应用LA-ICP-MS法测得石炭纪花岗岩U-Pb年龄为(296±3.5)Ma,结合区域构造演化特点及所测三叠纪花岗岩的地球化学特征认为,在晚石炭世,南蒙古额尔德尼查干地区已进入碰撞期构造环境,在三叠—侏罗纪仍有同碰撞花岗岩侵入,晚石炭世以后的碰撞期持续时间较长。     

东太平洋573孔始新世末渐新世纪地层特征及稀土元素地球化学

根据深海钻探样品分析，对东太平洋地区573孔始新世末渐新世初的地层进行了研究，尤其是研究了其稀土元素地球化学特征。各层球粒陨石标准化值曲线平缓，重稀土相对富集，各层Ce严重亏损（第2层轻度亏损），各层的Eu仅轻度亏损。始新世与渐新世的界线地层含钨粘土层的稀土元素含量明显比其它层含量高得多。此外，该层还富含Fe及指示地外成因的Ni、Co、Ir等元素，且底部富含微玻璃陨石。这些特征说明该含金属粘土层的形成与火山活动有显关系，其底部可能还与陨击作用相联系。从区域地质情况来看，始新世末期有明显的生物灭绝和环境变化，微玻璃陨石广泛发育，说明该时期明显的灾变事件发生。     

Correct nomenclature for the Angadimogar pluton, Kerala, southwestern India

The proper usage of modal composition and geochemical classification of granitoids is discussed for assigning a proper nomenclature for the Angadimogar pluton, Kerala, southwestern India. This discussion is mainly aimed at addressing questions concerning the nomenclature of Angadimogar pluton (syenitevs. granite). Modal composition and whole-rock XRD data clearly show that the pluton exposed near Angadimogar is a quartz-syenite and its geochemistry is typical of a ferroan, metaluminous, alkali (A-type) granitoid     

Facies of slurry-flow deposits, Britannia Formation (Lower Cretaceous), North Sea: implications for flow evolution and deposit geometry

ABSTRACT Mud‐rich sandstone beds in the Lower Cretaceous Britannia Formation, UK North Sea, were deposited by sediment flows transitional between debris flows and turbidity currents, termed slurry flows. Much of the mud in these flows was transported as sand‐ and silt‐sized grains that were approximately hydraulically equivalent to suspended quartz and feldspar. In the eastern Britannia Field, individual slurry beds are continuous over long distances, and abundant core makes it possible to document facies changes across the field. Most beds display regular areal grain‐size changes. In this study, fining trends, especially in the size of the largest grains, are used to estimate palaeoflow and palaeoslope directions. In the middle part of the Britannia Formation, stratigraphic zones 40 and 45, slurry flows moved from south‐west and south towards the north‐east and north. Most zone 45 beds lens out before reaching the northern edge of the field, apparently by wedging out against the northern basin slope. Zone 40 and 45 beds show downflow facies transitions from low‐mud‐content, dish‐structured and wispy‐laminated sandstone to high‐mud‐content banded units. In zone 50, at the top of the formation, flows moved from north to south or north‐west to south‐east, and their deposits show transitions from proximal mud‐rich banded and mixed slurried beds to more distal lower‐mud‐content banded and wispy‐laminated units. The contrasting facies trends in zones 40 and 45 and zone 50 may reflect differing grain‐size relationships between quartz and feldspar grains and mud particles in the depositing flows. In zones 40 and 45, quartz grains average 0·30–0·32 mm in diameter, ≈ 0·10 mm coarser than in zone 50. The medium‐grained quartz in zones 40 and 45 flows may have been slightly coarser than the associated mud grains, resulting in the preferential deposition of quartz in proximal areas and downslope enrichment of the flows in mud. In zone 50 flows, mud was probably slightly coarser than the associated fine‐grained quartz, resulting in early mud sedimentation and enrichment of the distal flows in fine‐grained quartz and feldspar. Mud particles in all flows may have had an effective grain size of ≈ 0·25 mm. Both mud content and suspended‐load fallout rate played key roles in the sedimentation of Britannia slurry flows and structuring of the resulting deposits. During deposition of zones 40 and 45, the area of the eastern Britannia Field in block 16/26 may have been a locally enclosed subbasin within which the depositing slurry flows were locally ponded. Slurry beds in the eastern Britannia Field are ‘lumpy’ sheet‐like bodies that show facies changes but little additional complexity. There is no thin‐bedded facies that might represent waning flows analogous to low‐density turbidity currents. The dominance of laminar, cohesion‐dominated shear layers during sedimentation prevented most bed erosion, and the deposystem lacked channel, levee and overbank facies that commonly make up turbidity current‐dominated systems. Britannia slurry flows, although turbulent and capable of size‐fractionating even fine‐grained sediments, left sand bodies with geometries and facies more like those deposited by poorly differentiated laminar debris flows.     

Geochemical Features of Ophiolite in Mianxian Lueyang Suture Zone，Qinling Orogenic Belt

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Platinum-group element distribution in chromite ores from ophiolite complexes: implications for their exploration

Compilation of some new data on ophiolites for Greece and Yugoslavia, and published data from previous studies, indicate that platinum-group element (PGE) and gold concentrations in chromite ores are generally low, ranging from less than 100 ppb to a few hundred ppb. However, samples from several ophiolite complexes exhibit an enrichment (of a few ppm) (a) only in Os, Ir and Ru,(b) only in Pt and/or Pd or (c) in all PGE. This enrichment (up to 10s ppm) is mainly related with chromitites hosted in supra-Moho dunites and dunites of the uppermost stratigraphic levels of the mantle sequence and it seems to be local, independent of the chromitite major element composition and the chromite potential of the ophiolite complexes. The contents of PGE combined with less chalcophile elements (Ni, Co, Cu), the ratios of incompatible/compatible elements, and PGE-patterns provide evidence for discrimination between chromitites derived from primitive magmas and those derived from partially fractionated magmas, although they have a similar major element composition. Thus, they can be used for a stratigraphic orientation in the mantle sequence, and therefore for exploration targets. Moreover, PGE data offer valuable information for the evaluation of the chromite potential in ophiolite complexes. The most promising ophiolites seem to be those which apart from the petrological and geochemical characteristics indicating extensive degree of partial melting in the mantle source contain only one chromite ore type (the other type being only in small proportion) of limited compositional variation, in both major elements and PGE, low ratios of , while PGE-enriched chromitites in the mantle sequence are only occasionally present. In contrast, ophiolites which contain both high-Cr and -Al chromitites, and where their chalcophile element data implies relatively extensive fractionation trend are not good exploration targets for chromite ores, although they are related with a SSZ environment.     

采矿环境地球化学研究

阐述了采矿对环境造成的负面影响 ,包括 :尾矿或废石堆中的杂质元素会进入表生地球化学循环 ,在不同气候条件下 ,呈现不同的特征模式 ,尾矿氧化带的酸性水的排放 ;矿山污染源对周围土壤和植物的影响使重金属元素等进入食物链 ,对人类和动物健康造成威胁。根据国内外的最新研究动向 ,指出建立环境地球化学模式 ,对采矿环境污染作出客观的监测和评价 ,能为防止污染和治理环境提供可靠的地球化学依据。