L'unité ophiolitique de Pineto (Corse) : signification du détritisme continental dans sa couverture de flysch albo-cénomanien

The Jurassic N-MORB ophiolites of the Pineto Unit, which were unaffected by Alpine metamorphism, can be compared to the Apennine ophiolites. They are, however, distinguished by their cover rocks that include a silico-clastic flysch that we have dated as Albian–Cenomanian. Clastic deposits of the same type, but coarser grained, are known from the normal cover rocks of the Balagne Nappe E-MORB ophiolites, originally located on a thinned continental crust and/or near a continental margin. The Pineto Unit thus indicates that the detrital input of continental material was able to extend to a domain of clearly oceanic character in the Ligurian palaeo-ocean. To cite this article: M. Durand-Delga et al., C. R. Geoscience 337 (2005).     

Porphyry Cu–Au mineralisation associated with a multi-phase intrusion, and related replacement fronts in limestones in an island arc setting near the Gümü hane village (Artvin) in the Eastern Black Sea Province (Turkey)

The Gümü hane area near Artvin is highly characteristic due to a significant hydrothermal alteration zone genetically associated with a microdiorite stock and its late-stage derivatives in the form of porphyry plugs that intruded into all the pre-Middle Eocene lithologies. The porphyry intrusion is multi-stage, intermediate to felsic in composition, and divided into pre-ore feldspar porphyries and quartz–feldspar porphyries, syn-ore feldspar–amphibole porphyries, and post-ore feldspar porphyries. Sericitic alteration is dominant, but K-silicate alteration is also observed and is characterised mainly by secondary feldspars, biotites, quartz, anhydrite, magnetite and pyrite veinlets. The central part of the alteration and the porphyry system where syn-ore feldspar–amphibole porphyry outcrops coincides with intense quartz stock-working with anomalous but uneconomical Cu and Au values. In this zone, pyrite is ubiquitous and is accompanied by chalcopyrite and lesser sphalerite, sulphosalts, molybdenite, bornite and magnetite. Chemical analyses of surface and drill core samples show that overall Au and Cu values are around 0.5 ppm and 0.3%, respectively, and that they are in the ranges of 1–2 ppm and 0.3–0.4%, respectively, in the densest stock-work zones.Multi-phase intrusion of porphyries into Late Cretaceous limestone also caused replacement fronts along re-crystallised limestone and porphyry contacts. This type of mineralisation is enriched in Mn, Zn, Cu, Au and Ba, and contains on average 4.7% MnO, 3.2% FeO, 3.1% Zn, 0.95% Cu, 0.3% Pb, 200 ppb Au, 900 ppm Bi and 660 ppm Ba, present in Fe- and Mn-oxides, pyrite, chalcopyrite, sphalerite and lesser bornite, sulphosalts and gold. Supergene oxidation is well developed in these zones.Hydrothermal alteration mass change calculations reflect an intimate relationship between the two types of mineralisation. The lithologies near mineralised fronts are highly depleted in MnO and Zn, and the intensity of depletion is reduced away from the contact into the porphyry. The leached elements are added to the re-crystallised limestone block in which MnO and Zn show an 81-fold and 472-fold increase, respectively, over the least altered limestone. Au and Cu are enriched along the contact both in the porphyry and in the limestone, implying that they may have been derived either from other lithologies in the vicinity or the magma itself.     

辽西八家子斑岩成矿分带系列的应用及其找矿效果

为了在八家子铅一锌一银矿田寻找新的矿种——钼矿，通过对八家子一杨家杖子成矿带上矿床特征的对比研究，认为此成矿带上每隔10km就出现一个矿集区，每个矿集区由数个或数十个矿床构成；在同一个矿集区中，围绕岩体这个成矿中心，金属矿化和成矿元素出现明显分带性。而八家子铅-锌-银矿床具有此类似特征。因此，提出八家子矿田存在一个完整的成矿分带系列，其成矿中心是炉沟的花岗斑岩体，岩体具备了寻找兰家沟式大型斑岩钼矿床的各种地质条件。此后，经对物化探异常的验证，发现八家子铅-锌-银多金属矿田的Mo异常内存在厚大钼矿体。     

内蒙古小东沟钼多金属矿床地质特征

阐述了小东沟钼多金属矿床的矿体、矿化蚀变、硫同位素等地质特征，初步确定成矿物质来源于深源岩浆。矿床属于与燕山早期晚阶段小东沟花岗岩体有关的斑岩型钼矿床—中低温铅锌矿床。     

内蒙古霍各乞铜多金属矿床的含矿建造及矿床成因分析

内蒙古霍各乞矿床是狼山地区著名的大型铜多金属矿床,含矿建造层序依次为中元古界陆缘裂谷拉斑玄武岩系→矿化热水沉积岩系→陆源碎屑岩系。拉斑玄武岩及基性侵入岩大部分变质为绿泥石片岩,但局部残留基性火山岩和辉长岩类变余结构构造,局部达到斜长角闪岩相,且w(Na2O)>w(K2O)。变余辉长岩的稀土总量较低,且轻、重稀土基本没有分异,黑云绿泥片岩的稀土总量较高,其配分曲线呈轻稀土富集、重稀土亏损型。黑云绿泥片岩中B、F、K、Ti、Zn、Rb、Sn、Nb、Ag、Ba、Pb、U相对富集,Cu、Pb、Zn富集系数高于变余辉长岩,表明绿泥石片岩具有热液蚀变的特征。含矿岩段条带状石英岩、透辉透闪石岩的稀土总量偏低,轻、重稀土有明显分异,并表现为特征的正Eu异常。除矿化富集外,微量元素Be、B、F、Rb、Ag、Ba、Th、U也有明显富集,表现了热水富集成因的特征。矿床矿化受岩性层控制的特征明显,并且在一定的构造部位富集,具有热液叠加改造的特征。硫同位素变化范围大,多表现为正值,硫化物δ34S值的大小排序为黄铁矿>磁黄铁矿>黄铜矿>方铅矿、闪锌矿。矿床成因分析表明霍各乞多金属矿床为热水沉积块状硫化物矿化叠加变质热液改造富集而形成的矿床。     

内蒙古北山东段珠斯楞铜金矿床的基本特征

珠斯楞铜金矿位于晚古生代板块缝合部位,产于华力西晚期花岗斑岩和闪长玢岩岩脉中,通过矿区基础地质、物化探等的研究,确定有2个矿体、1个矿化体。主要矿石矿物为黄铜矿、黄铁矿、磁黄铁矿、闪锌矿、方铅矿、毒砂等,呈浸染状、细脉状分布。化探垂直分带性表明,Au和前缘晕元素在浅部富集,Cu在中深部富集。矿床为斑岩型,主要发育青磐岩化带,其可作为区域上大型斑岩铜矿的找矿标志。     

德兴铜矿花岗闪长斑岩物质来源的微量元素研究

对德兴铜矿铜厂和富家坞花岗闪长斑岩样品的微量元素和稀土元素分配特征分析研究表明,铜厂和富家坞两个矿区的花岗闪长斑岩具有一致的来源,两个斑岩体均由混有少量地壳物质的地幔岩浆演化而来.结晶分异作用可能是岩浆演化的主要原因.     

准苏吉花敖包铜多金属矿控矿因素分析

准苏吉花敖包铜多金属矿区位于东乌旗-二连浩特多金属成矿带西段,地质情况复杂.因部分地层中含有碳质板岩,对地球物理工作的结果产生了一定的影响.通过结合地质、地球物理、地球化学特征分析,总结出了该区的找矿方向.     

4: Transpressional tectonics, lower crust decoupling and intrusion of deep mafic sills: A model for the unusual metallogenesis of SW Iberia

SW Iberia is interpreted as an accretionary magmatic belt resulting from the collision between the South Portuguese Zone and the autochthonous Iberian terrane in Variscan times (350 to 330 Ma). In the South Portuguese Zone, pull-apart basins were filled with a thick sequence of siliciclastic sediments and bimodal volcanic rocks that host the giant massive sulphides of the Iberian Pyrite Belt. Massive sulphides precipitated in highly efficient geochemical traps where metal-rich but sulphur-depleted fluids of dominant basinal derivation mixed with sulphide-rich modified seawater. Massive sulphides formed either in porous/reactive volcanic rocks by sub-seafloor replacement, or in dark shale by replacement of mud or by exhalation within confined basins with high biogenic activity. Crustal thinning and magma intrusion were responsible for thermal maturation and dehydration of sedimentary rocks, while magmatic fluids probably had a minor influence on the observed geochemical signatures.The Ossa Morena Zone was a coeval calc-alkaline magmatic arc. It was the site for unusual mineralization, particularly magmatic Ni–(Cu) and hydrothermal Fe-oxide–Cu–Au ores (IOCG). Most magmatism and mineralization took place at local extensional zones along first-order strike-slip faults and thrusts. The source of magmas and IOCG and Ni–(Cu) deposits probably lay in a large mafic–ultramafic layered complex intruded along a detachment at the boundary between the upper and lower crust. Here, juvenile melts extensively interacted with low-grade metamorphic rocks, inducing widespread anatexis, magma contamination and further exsolution of hydrothermal fluids. Hypersaline fluids (δ¹⁸O_fluid > 5.4‰ to 12‰) were focused upward into thrusts and faults, leading to early magnetite mineralization associated with a high-temperature (> 500 °C) albite–actinolite–salite alteration and subsequent copper–gold-bearing vein mineralization at somewhat lower temperatures. Assimilation of sediments by magmas led in turn to the formation of immiscible sulphide and silicate melts that accumulated in the footwall of the layered igneous complex. Further injection of both basic and sulphide-rich magmas into the upper crust led to the formation of Ni–(Cu)-rich breccia pipes.Younger (330 to 280 Ma?) peraluminous granitoids probably reflect the slow ascent of relatively dry and viscous magmas formed by contact anatexis. These granitoids have W–(Sn)- and Pb–Zn-related mineralization that also shows geochemical evidence of major mantle–crust interaction. Late epithermal Hg–(Cu–Sb) and Pb–Zn–(Ag) mineralization was driven by convective hydrothermal cells resulting from the high geothermal gradients that were set up in the zone by intrusion of the layered igneous complex. In all cases, most of the sulphur seems to have been derived from leaching of the host sedimentary rocks (δ³⁴S = 7‰ to 20‰) with only limited mixing with sulphur of magmatic derivation.The metallogenic characteristics of the two terranes are quite different. In the Ossa Morena Zone, juvenile magmatism played a major role as the source of metals, and controlled the styles of mineralization. In the South Portuguese Zone, magmas only acted as heat sources but seem to have had no major influence as sources of metals and fluids, which are dominated by crustal signatures. Most of the magmatic and tectonic features related to the Variscan subduction and collision seem to be masked by those resulting from transpressional deformation and deep mafic intrusion, which led to the development of a metallogenic belt with little resemblance to other accretionary magmatic arcs.     

Environmental study on a long history of Cu mining in Hubei, central China

The Tonglushan Cu mine situated in a densely populated, humid temperate ecoregional domain, so called the Birthplace of the Bronze age in the world, has been mined for over three thousand years. However, there is no significant pollution in surrounding area yet. To understand the mechanism controlling the environment the geological controls, including regional geology, deposit type, deposit size, host rocks, mineralogy, texture, alteration, ore controls, were studied by re-evaluating data from mineral exploration and mining activities; the geochemical factors including soils both in rice field and dry land, underground water and rice were investigated in 2003-2004. The results show that the ground water around the mine is not contaminated,