山东招远栾家河断裂北段表土矿物蚀变特征

经过对栾家河断裂北段表土矿物成分鉴定和化学分析,该研究区的表土来自经受过低温(<150℃)中至弱碱性热液作用的岩石,主要由斜长石、钾长石、白云母、石英、风化成因的高岭石和热液叠加而成的蒙脱石等矿物混合而成.根据表土矿物蚀变特征与已知矿化带顶部表土特征的对比,工作区内高岭石矿物主要为风化成因,而蒙脱石系热液作用而成.从蚀变粘土矿物特征推断,其深部存在热液金矿化.     

辽东裂谷Au、Ag、Pb、Zn、Cu、Co金属矿床地质特征和成矿条件

Au、Ag、Pb、Zn、Cu、Co是辽东裂谷最主要的金属矿床 ,产于辽河群的不同层位。矿床成因至少可分沉积—变质热液成因、岩浆热液成因和接触交代成因三类。成矿受含矿层、构造、岩浆活动和变质作用控制。矿源层是成矿前提 ,构造—岩浆活动是成矿必要条件。构造—岩浆活动叠加改造的矿源层是最佳的成矿和找矿地区。     

广西来宾蓬莱滩剖面中上二叠统硅质岩的地球化学特征及沉积背景

广西来宾地区中上二叠统广泛发育硅质岩,蓬莱滩剖面和铁桥剖面是本地区中上二叠统出露最好的剖面.本文对蓬莱滩剖面28件硅质岩(分别为中二叠统茅口组3件与上二叠统合山组25件)的主量和稀土元素进行了分析研究,并结合岩石学特征,认为:蓬莱滩剖面合山组硅质岩沉积于受到陆源物质影响的边缘海盆环境,它们的硅质主要来源于硅质生物,为生物成因;而其茅口组硅质岩则沉积于远离陆源物质影响的边缘海盆环境,它们的硅质主要来源于热液,为热液成因.通过与铁桥剖面的热液成因硅质岩的沉积背景对比研究,结果表明:中晚二叠世时期,来宾地区为富硅的边缘海盆环境,而陆源物质输入程度的差异是造成本地区形成不同成因硅质岩的主要因素.     

广西大厂锡多金属矿床方解石的REE地球化学特征

方解石是广西大厂锡多金属矿床矿石中重要的脉石矿物.对不同产状矿体中方解石的REE地球化学特征研究表明:方解石在不同类型矿体中REE含量、有关参数和稀土配分模式等均变化较大,但在地球化学特征上具有连续变化规律,显示同源不同阶段的产物;矿床的成矿流体具有岩浆来源的特征,不排除地幔来源的可能;成矿环境表现为还原向氧化环境的变化.     

Isotope geochemistry (S,C, O,Sr, Pb) of the Chaudfontaine mineralization (Belgium)

Investigations on S, C, O, Sr, and Pb isotopes in ores, gangue, and country rocks of the Chaudfontaine ore deposit confirm that interbedded barite and white sparry calcites are cogenetic. They emphasize the marine origin of S and the nonmarine origin of the metals. They underline the important role played by the bacterial reduction at the site of deposition. Hypotheses concerning the source of the metals and the nature of the brines involved in their transportation are briefly discussed.     

Chemical evidence for,and implications of,a primary FeS phase in the Ankarvattnet Zn-Cu-Pb massive sulphide deposit,central Swedish Caledonides

The origin of the pyrrhotite in the Ankarvattnet massive sulphide deposit is discussed, based on chemical relations between the different mineralization types. A metamorphic genesis is rejected and a premetamorphic origin is alternatively suggested, which is in agreement with similar ideas for the origin of the pyrrhotite in other deposits. The pyrrhotite is thought to have formed in the stringer zone to a massive pyritic layer with similar formation mechanisms as for volcanogenic massive sulphide deposits. The recognition of a stringer zone mineralogy provides better possibilities to understand the physico-chemical character of the ore forming environment.     

云南哀牢山金矿床的成矿条件

成矿作用包括矿物质的来源、搬运及沉淀的全过程,其中最活跃因素为成矿流体。可以说,没有流体就不会形成矿床,但也不是所有流体都成矿。笔者通过哀牢山蛇绿混杂岩带典型金矿床的物质组成、成矿规律、蚀变及控矿作用的研究,对哀牢山金矿带的成矿流体来源,成矿流体动力学、地球化学及物理化学性质进行了详细地讨论;对金矿的成矿物质来源,金在成矿流体中的存在形式,迁移过程中平衡、失稳－沉淀先进进行了详细地分析和探讨。     

Submarine origin for the Neoproterozoic Wonoka canyons,South Australia

An examination of the deeply incised Ediacaran Wonoka canyons in the Adelaide Geosyncline (most recently interpreted as subaerial valleys) demonstrates their submarine origin, and confirms them as some of the best examples of ancient outcropping submarine canyons in the world. The entire canyon-fill succession is interpreted to be of deep-water (below wave base) origin, consisting of calcareous shale and siltstone together with a variety of mass-flow deposits including turbidites, grain flows and debris flows. The canyon fill lacks definitive shallow-water structures (e.g. mud cracks, fenestral fabrics or wave ripples) at all stratigraphic levels. Canyon-lining carbonate crusts that have previously been interpreted as non-marine calcretes or tufas (and used to suggest a non-marine origin for the canyons) are argued to be of deep-water, marine, microbial origin. Extremely negative carbon isotope values from the canyon-fill and canyon-lining crusts have a primary marine origin. Previously interpreted deepening upward trends in the canyon fill (used as evidence of a subaerial erosion episode followed by drowning) are suggested to be fining upward trends, caused by the transition from canyon cutting to canyon filling, with the majority of the fill being of deep-water slope origin. The basal conglomeratic canyon-fill sediments represent the last vestiges of the high-energy, deep-water, canyon-erosion environment in which the incisions formed. A deep-water origin for the canyons is consistent with all previous stratigraphic observations of the Wonoka canyons, including the conspicuous lack of regional unconformities in the lower Wonoka Formation, and their emanation from the deep-water facies of the Wonoka Formation. A submarine canyon origin also removes the need for extreme (~ 1 km) relative sea level fluctuation and associated problems (i.e. an enclosed basin with Messinian-style evaporative drawdown or thermal uplift above a migrating mantle plume) required by the subaerial valley hypotheses.     

云南白牛厂银多金属矿床喷流沉积成因证据:容矿岩石的地球化学约束

滇东南是否存在广泛的热水沉积活动已成为制约滇东南三大多金属矿床(个旧、都龙、白牛厂)成因研究的主要因素之一。系统研究了白牛厂银多金属矿床容矿岩石的地球化学特征,研究表明:矿床容矿岩石主量元素数据均投影于火山及海底热卤水成因区域内;稀土元素明显分为两组,稀土元素总量较高的样品可能与较多的正常沉积物的加入有关;稀土元素总量较低的样品具有与加拿大沙利文矿山的条带状富电气石热液沉积岩和加拿大Agnico-Eugle矿山的铁建造中的条带状燧石岩相似的稀土元素配分模式与标准化参数;同时,微量元素对的演化趋势与现代大洋热水沉积物相似,而且As、Sb和Ag含量与大厂和个旧热水沉积硅质岩相当。推测白牛厂银多金属矿床属热水沉积成矿,只是在距花岗岩体较近的部位遭受了部分叠加改造。     

A morphological, sedimentological and geophysical investigation of the Woore Moraine, Shropshire, England

The Bar Hill-Whitchurch-Wrexham Morainic Complex is a large-scale glacial landform thought to represent either the maximum extent or the re-advance of the British-Irish Ice Sheet during the Late Devensian. The origin of the moraine remains uncertain as its key characteristics have not been studied in detail due to a lack of exposures from which its large-scale structure can be determined. The development of new technologies has enabled detailed examination of the topography and internal structure of such large-scale landforms. This paper describes a multi-disciplinary approach involving digital geomorphological mapping using enhanced resolution NextMAP™ digital surface models, geophysical imaging (electrical resistivity tomography) and conventional sedimentological analyses. This combination of techniques is useful for elucidating the origin of a large glacial landform in a region of poor exposure. Digital elevation models such as NextMAP™ offer an efficient and accurate method for landform-mapping, whilst electrical resistivity tomography was able to map the major constituent sediments of the moraine, which had in turn been identified in the single exposure available. Additional geophysical techniques should however be applied to provide further structural data and thereby enable a more detailed interpretation of the moraine's internal structure. Preliminary findings indicate that the moraine is a glaciotectonic landform composed of diamicton and glaciofluvial sediments, an origin consistent with recent suggestions that the Cheshire Plain contained an active ice lobe during the last glacial maximum.     

On the origin of non-tidal flaser bedding in point bar deposits of the river Ajay, Bihar and West Bengal, NE India

Flaser bedding of non-tidal origin has been described from point bar deposits of the Ajay river, NE India. Mud drapes are deposited during waning flood phases. The preferential accumulation of curled, desiccated mud laminae in ripple troughs during periods of exposure produces mud streaks resembling classical flaser bedding. This process of non-tidal flaser formation is unlike the common tidal origin related to flood and ebb cycles, and the less common mechanism of formation in fluvial systems by deposition of mud in ripple troughs after floods.     

新疆三塘湖盆地二叠系湖相白云岩形成机理初探

利用薄片染色、微量元素和稳定同位素测试等方法对三塘湖盆地中二叠统芦草沟组与湖相暗色泥岩共存的白云岩的形成机理进行了探讨。白云岩分为纹层状藻云岩和斑块白云岩两种类型。白云岩的微量元素和同位素特征表明其形成于较高盐度、高Mg/Ca比、强还原的沉积环境。通过对白云岩镁离子来源的分析,认为纹层状藻云岩形成于准同生期,而斑块白云岩则是在埋藏成岩期火山物质淋滤、交代作用下形成的。     

安徽铜陵地区成矿控制因素的探讨

铜陵地区是长江中下游铁铜硫金成矿带的重要成矿区。区内矿床众多，类型复杂，成因多样。为了查明本区的控矿因素，本文运用宏、微观相结合，地质观察研究与同位素、稀土元素等地球化学以及流体包裹体分析相结合的方法，区域地质背景、地层岩性、岩浆岩、构造及成矿流体性质等与成矿的关系，认为不同成因、不同类型的矿床所受的控制因素具有明显差异。     

Geochemistry of magmatic rocks of the Koksharovka alkaline-ultrabasic massif,primorye, and results of trace-element modeling

New geochemical data are presented on the magmatic rocks of the Late Jurassic Koksharovka alkaline-ultrabasic massif, which is associated with deposits of vermiculite, apatite, V-bearing titanomagnetite, and placer isoferroplatinum. The REE geochemistry and strontium, oxygen, and carbon isotopic composition of carbonatites and related ijolites and pyroxenites, together with geological observations, point to the magmatic origin of the Koksharovka carbonatites. The origin of associated magmatic rocks is discussed. Trace element modeling of partial melting of mantle sources was conducted to decipher the genesis of the melts of the Koksharovka carbonatites and host titanite-kaersutite pyroxenites.     

On the chemical composition of the ore breccia at Luossavaara,northern Sweden

An important argument for a magmatic affiliation of the Kiruna type of ore is the presence of ore breccia which accompany the main ore bodies. According to Parák (1975a and b) the main ore bodies are not of the same origin as the breccias. This is based on data from the Luossavaara deposit in northern Sweden: the main ore and the breccia have different chemical compositions. Microprobe analyses made in the present study, however, clearly demonstrate similarity in chemical composition, strengthening the hypothesis of a common origin for both formations.     

The Inka mummy from Mount Aconcagua: Decoding the geographic origin of the “Messenger to the Deities” by means of stable carbon,nitrogen, and sulfur isotope analysis

Human sacrifices were a ritual practice during the expansion of the Inka Empire. Nevertheless, the homeland of the victims has never been clearly determined. A mummy recently found in a mediterranean environment in the Andes of Argentina provides a unique opportunity to shed some light on the matter. His clothing and funerary trousseau give no evidence regarding his ethnic filiation, geographic origin, nor whether he belonged to the local population or to the Inka elite. Therefore, a decodification of his geographic origin was attempted. This was done through the reconstruction of his palaeodiet: A diet based on continental products would indicate a local origin whereas one including marine food would suggest ties with the Pacific littoral and, indirectly, a foreign origin. Carbon, nitrogen, and sulfur isotope ratios of the mummy's bone collagen and hair were compared with values from archaeological populations from littoral and altiplanic environments of South America. The carbon and nitrogen isotopic values of bone collagen were ambiguous tracers, indicating either a continental diet with a high percentage of maize, one including a certain amount of marine products, or a combination of both. The carbon and sulfur isotopic values of hair were conclusive, indicating a clear continental origin of the diet, at least during the period of a year and a half before death. © 1999 John Wiley & Sons, Inc.     

资阳地区震旦系灯影组白云岩成因研究

本文通过实际资料将资阳地区震旦系灯影组划分为四种主要岩石类型及三种主要沉积相。依据最新的白云岩成因理论,结合先进的室内测试手段,对这几类白云岩进行成因分析,证明资阳地区灯影组白云岩具原生和重结晶两种成因类型。     

Petrology, geochemistry and paleogeographic reconstruction of the East Sulawesi Ophiolite, Indonesia

The East Sulawesi Ophiolite (ESO) is tectonically dismembered and widely distributed in Central and East Sulawesi. It comprises, from base to top, residual mantle peridotite and mafic–ultramafic cumulate through layered to isotropic gabbro, to sheeted dolerites and basaltic volcanic rocks. Residual peridotite is dominantly spinel lherzolite intercalated with harzburgite and dunite. Ultramafic rocks from different locations display significant differences in rock composition and mineral. However, the clinopyroxene of peridotite displays REE pattern similarities with those of mid-ocean ridge (MOR) origin, rather than those of suprasubduction zone (SSZ) origin. The gabbroic unit consists of massive gabbro, layered gabbro, mafic and ultramafic cumulate and anorthosite. The observed crystallization sequence of gabbroic unit, which is olivine→(spinel)→plagioclase→clinopyroxene→(orthopyroxene)→(hornblende), and the mineral chemistry data indicate that the ESO gabbro has similarities with MOR setting.Major and trace element geochemistry of basalt and dolerite suggests MOR, oceanic plateau and minor SSZ origins. A possible oceanic plateau origin is supported by the following: (i) the 15-km thickness is comparable with the thickness of oceanic plateau rather than normal oceanic lithosphere; (ii) there are no or only minor olivine phenocrysts in the basalt; and (iii) predominance of aphyric texture in the basalts. The REE pattern of ESO basalt exhibits N-MORB-like signatures. However, a negative Nb anomaly in the trace element spider diagram may be attributed to mantle heterogeneity of an OPB source.The geochemical variations and disparities for both peridotite and basalt and the noncogenetic relationship between crust and mantle sections in several locations suggest that the ESO may have been formed at one tectonic setting and was later overprinted by magmatism in different environments through its birth to emplacement. A possible Cretaceous origin of an oceanic plateau component of the ESO is indicated on the basis of calculated paleopositions using plate trajectory analyses together with previously published paleolatitude data. The ESO can be traced back to the proximity of the presently active region of the SW Pacific Superplume.     

四川大宝山铜矿区矿床地质特征及找矿方向

层控矿床属火山-沉积变质成因;含铜石英脉型矿床为热液充填成因.根据成矿控制因素和找矿标志,对大宝山地区的成矿远景进行了划分,指出了进一步的找矿方向.     

Origin of the acidic volcanics of the Tolfa district,Tuscan Province,central Italy: an elemental and Sr-isotopic study

Volcanic rocks from the southern part of the Tuscan Province, the Tolfa district, range in composition from dacites to rhyolites. They have relatively high contents of many incompatible elements and their ⁸⁷Sr/⁸⁶Sr ratios vary between 0.7129 and 0.7148 (28 analyses) with one analysis of 0.7112. The four major eruption centres of the district can be distinguished geochemically. It is shown that the variation of major and trace elements within each area can be explained by fractional crystallization without significant crustal assimilation. The geochemical patterns of the incompatible elements of the investigated volcanics have a close similarity to the alkaline undersaturated volcanics from the nearby Roman Province. The geochemical and isotopic similarity between the Tolfa volcanics and those of the Roman Province suggests a common origin for these components of the magmas. It is suggested that, while the origin of the LIL-element enrichment of the Roman Province magmas is a mantle which was metasomatised by fluids or melts derived from upper crustal material of sedimentary origin recycled into the mantle by subduction, the Tolfa volcanics were derived directly from the subducted material by melting.