Neotectonic Characteristics of Central Anatolia

The Central Anatolian Crystalline Complex and its Tertiary cover have been highly dissected by neotectonic structures. The period of neotectonic activity is dominated by three main fault systems in Central Anatolia—the Tuzgolu fault zone, the Ecemis fault zone, and the Yozgat-Akdagmadeni-Bogazliyan fault system. The Tuzgolu fault zone, trending in a NW-SE direction, is located WSW of the Central Anatolian Crystalline Complex (CACC). This fault zone consists of parallel to subparallel, normal, and oblique right-lateral strike-slip faults displaying a step-like half-graben and horst-graben pattern. It controls the eastern margin of Tuzgolu, fault-parallel depressions, and the western margin of the Central Anatolian volcanic province. The Ecemis fault zone is located east of the CACC and is characterized by NE-SW-trending, left-lateral strike-slip faults controlling the eastern margin of the Central Anatolian volcanic province. The Yozgat-Akdagmadeni-Bogazliyan region is dominated by NW-SE- and NE-SW-trending conjugate faults. These three fault systems control the widely distributed Plio-Quaternary depressions, calc-alkaline-alkaline volcanic activity, and deposition of talus, alluvial fan, travertine, and terrace deposits. Alignment of hot springs, cinder cones, drainage offsets, and linear valleys are the characteristic features of strike-slip fault patterns observed in the region. Both morphotectonic features and recent earthquakes strongly suggest that most of the segments of these fault zones are stilt active.     

Petrogenesis of collision-related plutonics in Central Anatolia, Turkey

Central Anatolia exhibits good examples of calc-alkaline and alkaline magmatism of similar age in a collision-related tectonic setting (continent–island arc collision). In the Central Anatolia region, late Cretaceous post-collisional plutonic rocks intrude Palaeozoic–Mesozoic metamorphic rocks overthrust by Upper Cretaceous ophiolitic units to make up the Central Anatolian Crystalline Complex.

In the complex, three different intrusive rock types may be recognised based on their geochemical characteristics: (i) calc-alkaline (Behrekdag, Cefalikdag, and Celebi); (ii) subalkaline-transitional (Baranadag); and (ii) alkaline (Hamit). The calc-alkaline and subalkaline plutonic rocks are metaluminous I-type plutons ranging from monzodiorite to granite. The alkaline plutonic rocks are metaluminous to peralkaline plutons, predominantly A-type, ranging from nepheline monzosyenite to quartz syenite.

All intrusive rocks show enrichment in LILE and LREE relative to HFSE, and have high ⁸⁷Sr/⁸⁶Sr and low ¹⁴³Nd/¹⁴⁴Nd ratios. These characteristics indicate an enriched mantle source region(s) carrying a subduction component inherited from pre-collision subduction events. The tectonic discrimination diagram of Rb vs. (Y+Nb) suggests that the calc-alkaline, subalkaline, and alkaline plutonic rocks have been affected by crustal assimilation combined with fractional crystallisation processes.

The coexistence of calc-alkaline and alkaline magmatism in the Central Anatolian Crystalline Complex may be attributed to mantle source heterogeneity before collision. The former carries a smaller intraplate component and pre-subduction enrichment compared to the latter. Either thermal perturbation of the metasomatised lithosphere by delamination of the thermal boundary layer (TBL), or removal of a subducted plate (slab breakoff) is the likely mechanism for the initiation of the post-collisional magmatism in the Complex.     

Formation and emplacement ages of the SSZ‐type Neotethyan ophiolites in Central Anatolia,Turkey: palaeotectonic implications

Isolated outcrops of ophiolitic rocks, termed the Central Anatolian Ophiolites, are found as allochthonous bodies in the Central Anatolian Crystalline Complex, that represent the metamorphosed passive northern edge of the Tauride–Anatolide Platform, central Turkey. In terms of pseudostratigraphic relationships of the magmatic units and their chemical designation, the Central Anatolian Ophiolites exhibit a supra‐subduction zone (fore‐arc) setting within the Vardar–İzmir–Ankara–Erzincan segment of the Neotethys. The epi‐ophiolitic sedimentary cover of the Central Anatolian Ophiolites is generally characterized by epiclastic volcanogenic deep‐sea sediments and debris flows intercalated with pelagic units. The richest and most significant planktonic foraminiferal association recorded from the lowest pelagic members infer a formation age of early–middle Turonian to early Santonian. K/Ar ages of post‐collisional granitoids (81–65 Ma) intruding the basement rocks as well as the Central Anatolian Ophiolites suggest a post‐early Santonian to pre‐middle Campanian emplacement age. The marked high volume of epiclastic volcanogenic sediments intercalated with the pelagics of the Central Anatolian Ophiolite is suggestive of rifting in a marginal sea adjacent to a volcanic arc. Penecontemporaneous tectonism is reflected in repetitions in the stratigraphy and in debris flows, which result from major slides and mass‐gravity reworking of pre‐existing units and of arc‐derived volcanics and sediments. Correlating the rock units and formation/obduction ages of the Central Anatolian Ophiolites with further supra‐subduction zone type ophiolites in the eastern (Turkey) and western (Greece) parts of the Vardar–İzmir–Ankara–Erzincan segment of Neotethys we conclude that the intraoceanic subduction in the east is definitely younger and the closure history of this segment is more complex than previously suggested. Copyright © 2000 John Wiley & Sons, Ltd.     

Extrusive Members of Postcollisional A-Type Magmatism in Central Anatolia: Karahidir Volcanics,Idis Dagi-Avanos Area,Turkey

The Idis Dagi Igneous Complex is one of a number of late-stage plutonic bodies within the Central Anatolian Crystalline Complex. It intrudes Paleozoic-Mesozoic metamorphic basement rocks and Late Cretaceous granitoids. The complex comprises mainly quartz syenites and alkali-feldspar quartz syenites known as the Idis Dagi Syenitoids.

Trachydacitic, trachyandesitic, and dacitic rocks (Karahidir Volcanics) have been recently found as dikes cutting the Idis Dagi Syenitoids or as huge blocks within an olistostromal unit of latest Cretaceous(?)-Early Paleocene age that immediately overlies the Idis Dagi Igneous Complex. Petrographic and geochemical data indicate that the Idis Dagi Syenitoids and the Karahidir Volcanics display similar humped patterns on chondrite- and MORB-normalized spider diagrams, with peaks at Rb, Th, and Ce, and also negative Nb anomalies. These features are similar to patterns considered typical of postcollisional, A-type igneous rocks. A postcollisional setting is also suggested by the distribution of data on tectonic discrimination diagrams involving Nb, Y, and Rb. As a whole, the geochemical data suggest that the Idis Dagi Syenitoids and Karahidir Volcanics are cogenetic. Thus, the Karahidir Volcanics represent the shallow intrusive and volcanic equivalents of the deeper-level Idis Dagi Syenitoids.

The syenitoid rocks are considered the final phase of the magmatism in the Central Anatolian Crystalline Complex and are classified as post-orogenic alkaline rocks. Their chemical features suggest a largely mantle-derived magma contribution, together with a noticeable crustal component in their genesis. They were formed during postcollisional uplift that followed crustal thickening related to the southward emplacement of ophiolitic nappes during closure of the Izmir-Ankara-Erzincan Oceanic strand of Neotethys. The Karahidir Volcanics were exposed during regional extension that resulted in the formation of latest Cretaceous(?)-Early Paleocene extensional basins, and were emplaced as huge blocks into the continental clastic rocks by gravity sliding. This extension phase is characteristic of the development of all the other latest Cretaceous-Early Tertiary intracratonic basins in central Anatolia.     

Geologic and Tectonic Setting of the Yozgat Batholith,Northern Central Anatolian Crystalline Complex,Turkey

The Yozgat Batholith lies along the northern edge of the Central Anatolian Crystalline Complex in Central Anatolia, Turkey. The batholith intruded the Paleozoic-Mesozoic metamorphics and Cretaceous ophiolitic mélange, and was nonconformably overlain by latest Maastrichtian-Paleocene and/or Eocene clastics, carbonates, and volcanics. The batholith itself may be subdivided into several mappable subunits bounded by Cretaceous ophiolitic mélange, Eocene cover, and/or faults.

Major- and trace-element as well as REE analyses of the subunits indicate that the granitoids of the Yozgat Batholith are principally metaluminous monzogranites, of subalkaline-calc-alkaline character, except for the peraluminous leucogranitoids of the Yozgat subunit. The granitoids were derived by thickening of the continental crust and related partial melting; the thickening was caused by emplacement of ophiolitic nappes during collisional events.     

华南隐伏-半隐伏脉钨矿床的地表标志带

一、脉钨矿床的形态分带和标志带概念华南地区的脉钨矿床,多与花岗岩有成因上的联系。按工业矿脉与成矿岩体的空间关系,可将脉钨矿床分成三类,即外接触带矿床、内接触带矿床和内外接触带矿床。这三类矿床都具有形态分带性。外接触带和内外接触带矿床的形态分带特征基本相同,发育良好、保存完全者在垂直方向上综观可作五形变分带,即自上而下为线脉带、细脉带、薄脉带、大脉带、消失带。下部大、薄脉是上部线、细脉合并变大而成的。内接触带矿床只能分出三个     

Petrology of the Kurancali Phlogopitic Metagabbro: An Island Arc-Type Ophiolitic Sliver in the Central Anatolian Crystalline Complex

The Kurancali metagabbro occurs as an isolated body in the central part of the Central Anatolian Crystalline Complex. It has been emplaced along a steep S-vergent thrust-plane onto the uppermost units of the Central Anatolian Metamorphics. The main body of the Kurancali metagabbro is characterized by distinct compositional layering. The layered gabbros comprise pyroxene and hornblende gabbros. Phlogopite-rich, plagioclase-hornblende gabbro occurs mainly as pegmatitic dikes intruding the layered gabbro sequence. The layered gabbros, in general, consist mainly of diopsidic augites, brown hornblendes, and plagioclase. Secondary phases are phlogopitic mica, brownish-green hornblende replacing clinopyroxenes, and fibrous, greenish actinolitic hornblende partially or completely replacing brown hornblende. The primary dark micas are phlogopitic in the range of phlogopite_(57-70) and annite_(30-43). The analyzed pyroxenes are diopsidic (En₃₂Fs₁₉Wo₄₉-En₃₅Fs₁₈Wo₄₈).

The whole-rock geochemistry of the gabbros indicates the presence of two distinct groups of rocks; a less pronounced group of phlogopite gabbro with island-arc calc-alkaline affinities, and a dominating layered gabbro sequence with island-arc tholeiite characteristics. They are extremely enriched in LILE, indicative of alkaline metasomatism in the source region, and display geochemical features of transitional backarc-basin basalts (BABB)/island-arc basalts (IAB)—and IAB-type oceanic crust. Based on their geochemical similarities to modern island-arc basements, we suggest that the Kurancali metagabbro may represent the basement of an initial island arc, generated in a suprasubduction zone setting within the Izmir-Ankara branch of Neotethys.     

A Review of the Nature of Magmatism in Central Anatolia during the Mesozoic Post-Collisional Period

Magmatism in central Anatolia is characterized by petrographically and chemically distinct granitic and syenitic rocks. The granitic magmatism comprises C-type (crustal-derived) and H-type (hybrid) monzogranites and monzonites. Garnet-bearing C-type leucogranites represent the oldest magmatic phase, but younger hornblende ± biotite ± K-feldspar H-type plutons dominate the geology of the Central Anatolian Crystalline Complex (CACC). These typically include mafic microgranular enclaves. The granitic magmatism predates syenitic intrusions, among which quartz-bearing syenites were emplaced prior to feldspathoid-bearing ones.

The nature of magmatism in central Anatolia varies through time from peraluminous to metaluminous to alkaline. These different magma types reflect distinct stages of postcollisional magmatism, in which interaction between crust and mantle varied considerably. The C-type granites of the early stages of postcollisional magmatism were likely derived by partial melting of the lower continental crust induced by mafic magma underplating as a result of lithospheric delamination. The H-type granites and syenites of the mature and advanced stages of postcollisional magmatism indicate a significant contribution from mande-derived magma within a continuous or episodic extensional tectonic regime.     

Isobaric cooling and anti-clockwise P–T paths in the Variscan Odenwald Crystalline Complex, Germany

Mineral assemblages in Al₂O₃‐rich, SiO₂‐ and K₂O‐poor metapelitic rocks from the western Odenwald Crystalline Complex (Variscan Mid‐German Crystalline Rise, southern Germany) include corundum, spinel, cordierite, sillimanite, garnet and staurolite. Quartz is absent from almost all samples. Therefore, the applicability of conventional geothermobarometry is very limited or even impossible. Detailed petrographic investigation on selected samples permits inference of the sequence of appearance and disappearance of several mineral assemblages. The recognition of such partial re‐equilibration stages and their associated mineral assemblages, together with mineral stabilities predicted from KFMASH pseudosections, enables the determination of the pressure‐temperature (P–T) trajectories experienced by these rocks during the Variscan metamorphism. The rocks were metamorphosed under low‐P/high‐T conditions and underwent an anti‐clockwise P–T evolution. A pressure increase from about 2 kbar to 4 ± 0.5 kbar was accompanied by heating. Peak metamorphic conditions were reached at pressures of 4 ± 0.5 kbar and temperatures of at least 640 °C, probably even higher. The retrograde evolution is characterised by near‐isobaric cooling from ≥ 640 °C to approximately 550 °C. The rocks underwent the anti‐clockwise evolution in a subduction‐related magmatic arc setting. The close spatial association of the low‐P/high‐T rocks with recently discovered metabasic eclogites in the eastern part of the Odenwald Crystalline Complex may indicate a fossil paired metamorphic belt in the Central European Variscides.     

Petrotectonic Summary of Less Intensively Studied UHP Regions

This paper summaries tectonic settings and mineral parageneses of several recognized ultrahigh-pressure (UHP) terranes other than the well-studied Kokchetav Massif of northern Kazakhstan, the Western Gneiss Region of Norway, the Dora-Maira massif of the Western Alps, and the Dabie-Sulu terrane of east-central China. Diamond-bearing terranes include the Beni Bousera/Ronda peridotite massif, the Erzgebirge Crystalline Complex, mantle peridotite from a Tibetan ophiolite, and possibly the Maksyutov Complex. Coesite-bearing UHP terranes are the Zermatt-Saas area, Western Alps; the Mali eclogites from West Africa; the Makabal complex of western Tien Shan; the Bohemian massif; and the newly reported Central Indonesia terrane and Himalayan eclogites from the upper Kaghan Valley of Pakistan. Except for the diamond-bearing Tibetan ophiolite, most UHP terranes share similar petrotectonic assemblages and lie within major continental collision belts in Eurasia and Africa. Using new approaches (including new geobarometers) and technologies, additional UHP terranes are expected to be recognized in other Phanenorozic orogenic sutures.     

First evidence of a distal early Holocene ash layer in Eastern Mediterranean deep-sea sediments derived from the Anatolian volcanic province

A hitherto unknown distal volcanic ash layer has been detected in a sediment core recovered from the southeastern Levantine Sea (Eastern Mediterranean Sea). Radiometric, stratigraphic and sedimentological data show that the tephra, here termed as S1 tephra, was deposited between 8970 and 8690 cal yr BP. The high-silica rhyolitic composition excludes an origin from any known eruptions of the Italian, Aegean or Arabian volcanic provinces but suggests a prevailing Central Anatolian provenance. We compare the S1 tephra with proximal to medial-distal tephra deposits from well-known Mediterranean ash layers and ash fall deposits from the Central Anatolian volcanic field using electron probe microanalyses on volcanic glass shards and morphological analyses on ash particles. We postulate a correlation with the Early Holocene ‘Dikkart?n’ dome eruption of Erciyes Da? volcano (Cappadocia, Turkey). So far, no tephra of the Central Anatolian volcanic province has been detected in marine sediment archives in the Eastern Mediterranean region. The occurrence of the S1 tephra in the south-eastern part of the Levantine Sea indicates a wide dispersal of pyroclastic material from Erciyes Da? more than 600 km to the south and is therefore an important tephrostratigraphical marker in sediments of the easternmost Mediterranean Sea and the adjacent hinterland.     

Temporal and spatial distribution,deposit type and tectonic setting of East Tianshan tungsten deposit. Acta Petrologica SinicaSCIEI北大核心CSCD

东天山是中亚增生造山带的重要组成部分,蕴含了重要的铁、铜、镍、铅锌、金、钼、铷等矿床。近年来,东天山地区陆续发现了十余个大中型钨矿床,有望成为重要的钨矿资源基地。本文介绍了东天山地区钨矿床的地质特征、时空分布与构造背景,总结了东天山钨矿成矿规律,开展了成矿预测。东天山地区钨矿类型主要包括矽卡岩型、石英脉型及云英岩型,钨矿床的空间分布明显受控于前寒武纪结晶基底,成矿时间主要聚焦于三叠纪和晚石炭世。其中,中天山地块的矽卡岩型钨矿和东南缘的石英脉型钨矿形成于三叠纪,而中天山西南缘的矽卡岩型钨矿形成于晚石炭世,均与洋盆闭合之后的碰撞造山作用有关。根据东天山地区钨矿成矿规律,本文认为东天山地区钨矿找矿潜力巨大,提出了“前寒武纪基底+花岗岩+化探异常”的钨矿找矿预测思路,针对不同尺度的钨矿找矿勘查提出了建议。     

Neotectonic evolution of the northwestward arched segment of the Central Anatolian Fault Zone,Central Anatolia,Turkey

Central Anatolia has undergone complex Neotectonic deformation since Late Miocene–Pliocene times. Many faults and intracontinental basins in this region were either formed, or have been reactivated, during this period. The eastern part of central Anatolia is dominated by a NE–SW-trending, left lateral transcurrent structure named the Central Anatolian fault zone located between Sivas in the northeast and west of Mersin in the southwest. Around the central part, it is characterized by transtensional depressions formed by left stepping and southward bending of the fault zone.Pre-Upper Miocene basement rocks of the region consist of the central Anatolian crystalline complex and a sedimentary cover of Tertiary age. These rock units were strongly deformed by N–S convergence. The entire area emerged to become the site of erosion and formed a vast plateau before the Late Miocene. A NE–SW-trending extensional basin developed on this plateau in Late Miocene–Early Pliocene times. Rock units of this basin are characterized by a thick succession of pyroclastic rocks intercalated with calcalkaline–alkaline volcanics. The volcanic sequence is unconformably overlain by Pliocene lacustrine–fluviatile deposits intercalated with ignimbrites and tuffs. Thick, coarse grained alluvial/colluvial fan deposits of marginal facies and fine grained clastics and carbonates of central facies display characteristic synsedimentary structures with volcanic intercalations. These are the main lines of evidence for development of a new transtensional Hırka–Kızılırmak basin in Pliocene times. Reactivation of the main segment of the Central Anatolian fault zone has triggered development of depressions around the left stepping and southward bending of the central part of this sinistral fault zone in the ignimbritic plateau during Late Pliocene–Quaternary time. These transtensional basins are named the Tuzla Gölü and Sultansazlığı pull-apart basins. The Sultansazlığı basin has a lazy S to rhomboidal shape and displays characteristic morphologic features including a steep and stepped western margin, large alluvial and colluvial fans, and a huge composite volcano (the Erciyes Dağı).The geometry of faulting and formation of pull-apart basins can be explained within the framework of tectonic escape of the wedge-like Anatolian block, bounded by sinistral East Anatolian fault zone and dextral North Anatolian transform fault zone. This escape may have been accomplished as lateral continental extrusion of the Anatolian Plate caused by final collision of the Arabian Plate with the Eurasian Plate.     

加拿大拜韦尔特半岛金-铜矿集区成矿地质背景与矿床特征

拜韦尔特半岛矿产资源主要包括铜、金和石棉,区域地层和构造是控制矿床形成、发展和叠加改造的主要因素。这些矿产资源主要赋存在拜韦尔特海洋带达利吉带圣母玛利亚亚带的早奥陶世潜次火山岩中,包括起源于超俯冲作用带的蛇绿岩套和火山岩盖层。其蛇绿岩套超镁铁堆积岩的热液蚀变岩中产出石棉,火山成因的块状硫化物型(VMS型)铜±金矿产在基性和双峰式火山岩中,金矿产在基性和超基性的热液蚀变岩中。而蛇绿岩套火山岩盖层中则产出与条带状含铁建造(BIF)有关的后生金矿,石英脉型或相关的交代型矿床则大多赋存在蚀变和变形的基性岩中。拜韦尔特半岛的构造样式和几何结构非常复杂。     

Neotectonic evolution of the northwestward arched segment of the Central Anatolian Fault Zone,Central Anatolia,Turkey

Abstract

Central Anatolia has undergone complex Neotectonic deformation since Late Miocene-Pliocene times. Many faults and intracontinental basins in this region were either formed, or have been reactivated, during this period. The eastern part of central Anatolia is dominated by a NE-SW-trending, left lateral transcurrent structure named the Central Anatolian fault zone located between Sivas in the northeast and west of Mersin in the southwest. Around the central part, it is characterized by transtensional depressions formed by left stepping and southward bending of the fault zone. Pre-Upper Miocene basement rocks of the region consist of the central Anatolian crystalline complex and a sedimentary cover of Tertiary age. These rock units were strongly deformed by N-S con- vergence. The entire area emerged to become the site of erosion and formed a vast plateau before the Late Miocene. A NE-SW- trending extensional basin developed on this plateau in Late Miocene-Early Pliocene times. Rock units of this basin are characterized by a thick succession of pyroclastic rocks intercalated with calcalkaline-alkaline volcanics. The volcanic sequence is uncon- formably overlain by Pliocene lacustrine-fluviatile deposits interrelated with ignimbrites and tuffs. Thick, coarse grained alluvial/colluvial fan deposits of marginal facies and fine grained elastics and carbonates of central facies display characteristic synsedimentary structures with volcanic intercalations. These are the main lines of evidence for development of a new transtensional H?rka— k?zd?rmak basin in Pliocene times. Reactivation of the main segment of the Central Anatolian fault zone has triggered development of depressions around the left stepping and southward bending of the central part of this sinistral fault zone in the ignimbritic plateau during Late Pliocene-Quaternary time. These transtensional basins are named the Tuzla Gölü and Sultansazl??? pull-apart basins. The Sultansazl??? basin has a lazy S to rhomboidal shape and displays characteristic morphologic features including a steep and stepped western margin, large alluvial and colluvial fans, and a huge composite volcano (the Erciyes Da??).

The geometry of faulting and formation of pull-apart basins can be explained within the framework of tectonic escape of the wedgelike Anatolian block, bounded by sinistral East Anatolian fault zone and dextral North Anatolian transform fault zone. This escape may have been accomplished as lateral continental extrusion of the Anatolian Plate caused by final collision of the Arabian Plate with the Eurasian Plate. © 2001 Éditions scientifiques et médicales Elsevier SAS     

闽中地区次火山-热液金（银）矿床成矿系列及资源潜力

闽中地区是福建省金银成矿集中区,其上规模成矿主要集中于晚侏罗世次火山活动阶段。次火山-热液金(银)矿床的形成,矿、热、水“三源”是基本必要条件,北西、北东向两组构造带的复合是成矿定位的关键。在断隆带、坳中隆、坳中凹不同构造环境中,相应地递次形成(次)辉绿岩-闪长玢岩、(次)英安斑岩、(次)流纹斑岩等区域次火山-热液金(银)矿床成矿系列的3个亚系列;在垂向空间分布上,自上而下构成(微)细粒浸染型、石英脉型、破碎带蚀变岩型、隐爆角砾岩型、次火山岩型等工业矿床类型分带序列。金矿资源潜力在50t以上。     

Mineral Deposit Densities for Estimating Mineral Resources

Estimates of numbers of mineral deposits are fundamental to assessing undiscovered mineral resources. Just as frequencies of grades and tonnages of well-explored deposits can be used to represent the grades and tonnages of undiscovered deposits, the density of deposits (deposits/area) in well-explored control areas can serve to represent the number of deposits. Empirical evidence presented here indicates that the processes affecting the number and quantity of resources in geological settings are very general across many types of mineral deposits. For podiform chromite, porphyry copper, and volcanogenic massive sulfide deposit types, the size of tract that geologically could contain the deposits is an excellent predictor of the total number of deposits. The number of mineral deposits is also proportional to the type’s size. The total amount of mineralized rock is also proportional to size of the permissive area and the median deposit type’s size. Regressions using these variables provide a means to estimate the density of deposits and the total amount of mineralization. These powerful estimators are based on analysis of ten different types of mineral deposits (Climax Mo, Cuban Mn, Cyprus massive sulfide, Franciscan Mn, kuroko massive sulfide, low-sulfide quartz-Au vein, placer Au, podiform Cr, porphyry Cu, and W vein) from 108 permissive control tracts around the world therefore generalizing across deposit types. Despite the diverse and complex geological settings of deposit types studied here, the relationships observed indicate universal controls on the accumulation and preservation of mineral resources that operate across all scales. The strength of the relationships (R ²=0.91 for density and 0.95 for mineralized rock) argues for their broad use. Deposit densities can now be used to provide a guideline for expert judgment or used directly for estimating the number of most kinds of mineral deposits.     

一种新类型铜矿床的地球化学特征及其热水沉积成因

对兰坪－思茅沉积盆地几个代表性脉状铜矿床的研究发展，矿石构造以角砾状为主；金属矿物组合中出现较多的黝铜矿系列矿物（Ｃｕ１２Ｓｂ４Ｓ１３－Ｃｕ１２Ａｓ４Ｓ１３），约占金属矿物总量的５０％以上，部分矿石达８０％以上，其中尤以砷黝铜矿占优势；矿床的元素组合以Ｃｕ－Ａｓ－Ｓｂ－Ａｇ－Ｚｎ－（Ａｕ）－（Ｈｇ）－（Ｃｏ）－（Ｇａ）为特征；脉石矿物的稀土元素表现出特异的富中组稀土（Ｓｍ－Ｈｏ）、弱或无铕异常的曲     

La Formation glaciaire de la Mambéré (République Centrafricaine): Reconstitution paléogéographique et implications à l'échelle du Paléozoique africain

The Mambéré Formation constitutes a horizontal unit located in the western and southwestern part of the Central African Republic. Stratigraphical and sedimentological study provides strong argument to attribute these deposits a glacial origin. A palaeogeographical reconstruction has been outlined in order to precise the age of the formation. Two main categories of glacial deposits have been recognized:

glaciogenic deposits made of basal tills (with facetted pebbles) and flow tills (with flattened blunt pebbles);

reworked glacial deposits formed of sandstones and conglomeratic sandstones, in continuous beds, lenses or isolated blocks, together with siltstones and bedded sandstones.

The southerly provenance of the detrital material is demonstrated by quartz grain surface analysis and heavy-mineral study. This material results essentially from the dismantling of the Precambrian Schistoquartzitic Complex and secondarily from the Granitogneissic Complex. According to the palaeomagnetic polar paths and the migration of the glacial centers over the African continent during the Palaeozoic, the Mambéré Formation may be attributed a Lower Silurian age by reference to similar formations observed in Cameroon or a Lower Carboniferous age by comparison with the glacial formations reported from Niger and Egypt.     

A review of the occurrence, form and origin of C-bearing species in the Khibiny Alkaline Igneous Complex, Kola Peninsula, NW Russia

The Khibiny Complex hosts a wide variety of carbon-bearing species that include both oxidized and reduced varieties. Oxidised varieties include carbonate minerals, especially in the carbonatite complex at the eastern end of the pluton, and Na-carbonate phases. Reduced varieties include abiogenic hydrocarbon gases, particularly methane and ethane, dispersed bitumens, solid organic substances and graphite. The majority of the carbon in the Khibiny Complex is hosted in either the carbonatite complex or within the so-called “Central Arch”. The Central Arch is a ring-shaped structure which separates khibinites (coarse-grained eudialite-bearing nepheline-syenites) in the outer part of the complex from lyavochorrites (medium-grained nepheline-syenites) and foyaites in the inner part. The Central Arch is petrologically diverse and hosts the major REE-enriched apatite–nepheline deposits for which the complex is best known. It also hosts zones with elevated hydrocarbon (dominantly methane) gas content and zones of hydrothermally deposited Na-carbonate mineralisation. The hydrocarbon gases are most likely the product of a series of post-magmatic abiogenic reactions. It is likely that the concentration of apatite-nepheline deposits, hydrocarbon gases and Na-carbonate mineralisation, is a function of long lived fluid percolation through the Central Arch. Fluid migration was facilitated by stress release during cooling and uplift of the Khibiny Complex. As a result, carbon with a mantle signature was concentrated into a narrow ring-shaped zone.