Formation of lode‐style gold mineralisation during Tabberabberan wrench faulting at Lefroy,eastern Tasmania

The Lefroy Goldfield in eastern Tasmania is anomalous in southeastern Australia because mineralised fault reefs (i.e. reefs that are also faults) strike in an easterly direction at a high angle to the predominantly northwest strike of bedding and folds. Gold mineralisation is of Early to Middle Devonian age, with reef formation coinciding with a third regionally compressive deformation event (D₃), and a second phase of Tabberabberan orogenesis. Mineralised reefs are hosted by Mathinna Supergroup turbidites of Cambrian to Ordovician age and extend for up to 2 km across the boundary between the sandstone‐dominated Stony Head Sandstone and the shale‐dominated Turquoise Bluff Slate. Ore shoots in the reefs plunge moderately west and, in the Volunteer Mine, coincide with the intersection of the reef and a D₁/D₂ thrust contact. The subvertical orientation and discordant relationship of the mineralised reefs to bedding, as well as the lack of gold mineralisation along bedding and pre‐D₃ structures, indicate that the reefs formed during a period of wrench faulting. In contrast to lode‐style deposits in Victoria, the far‐field minimum compressive stress at Lefroy during reef formation was not vertical but, rather, occupied a subhorizontal orientation.     

Kilometre-scale structural setting of ore shoots in the Frasers gold deposit,Macraes mine,New Zealand

The Hyde-Macraes Shear Zone in southern New Zealand contains the circa 10 million ounce Macraes gold deposit, one of the larger Phanerozoic orogenic gold deposits discovered to date globally. Approximately 50% of this 10 million ounce resource is hosted by 5 major ore shoots up to 400 m wide and 1500 m long in the Frasers area at the southern end of the mine. Higher grade (>1.5 g/t Au) ore shoots are located along and immediately below the Hangingwall Shear, the principal strand of the Hyde-Macraes Shear Zone at the Frasers deposit. They typically trend parallel to the intersection of the shear and foliation in the underlying schist, commonly where the foliation dips more steeply that the overlying Hangingwall Shear. Especially thick zones of higher grade mineralised rock are located between the Hangingwall Shear and underlying second order splay shears whose position correlates with minor right-hand bends in the strike of the overlying Hangingwall Shear. Lower grade (<1.2 g/t Au), but economically significant, ore shoots are located within mineralised schists below the Hangingwall Shear. Outer margins of these lower grade ore shoots are generally parallel to the strike of the foliation in the host schist. They are most extensive where open disharmonic folding has resulted in the strike of the foliation diverging from that of the overlying Hangingwall Shear. No correlation exists between the position of any ore shoots and gently dipping jogs in the Hangingwall Shear, despite mineralisation occurring during reverse movement on the Hyde-Macraes Shear Zone. Instead the angular relationship between various strands of the Hyde-Macraes Shear Zone at Frasers and foliation in underlying schists is the most consistent structural feature likely to predict the location, extent, and orientation of ore shoots within the Frasers segment of the Hyde-Macraes Shear Zone.     

Deformation Mechanisms of Darreh Sary Metapelites,Sanandaj‒Sirjan Zone,Iran

The Darreh Sary metapelitic rocks are located in the northeast of Zagros orogenic belt and Sanandaj-Sirjan structural zone. The lithological composition of these rocks includes slate, phyllite, muscovitebiotite schist, garnet schist, staurolite-garnet schist and staurolite schist. The shale is the protolith of these metamorphic rocks, which was originated from the continental island arc tectonic setting and has been subjected to processes of Zagros orogeny. The deformation mechanisms in these rocks include bulging recrystallization (BLG), subgrain rotation recrystallization (SGR) and grain boundary migration recrystallization (GBM), which are considered as the key to estimate the deformation temperature of the rocks. The estimated ranges of deformation temperature and depth in these rocks show the temperatures of 275–375, 375–500, and >500°C and the depths of 10 to 17 km. The observed structures in these rocks such as faults, fractures and folds, often with the NW-SE direction coordinate with the structural trends of Zagros orogenic belt structures. The S-C mylonite fabrics is observed in these rocks with other microstructures such as mica fish, σ fabric and garnet deformation indicate the dextral shear deformation movements of study area. Based on the obtained results of this research, the stages of tectonic evolution of Darreh Sary area were developed.     

Geology of the Ranger Uranium Mine, Northern Territory, Australia: structural constraints on the timing of uranium emplacement

The geology of the No 1 and 3 pits at the Ranger Mine in the Pine Creek Inlier (PCI) of Australia is dominated by Palaeoproterozoic volcanic, carbonate and sedimentary sequences that unconformably overlie Archaean granitic gneiss of the Nanambu Complex (2470±50 Ma). These sequences are folded, faulted and sheared, and crosscut by east-trending granite (sensu stricto) dykes and pegmatite veins, and gently dipping N–NE trending mafic dykes of the Oenpelli Dolerite (1690 Ma). Regional metamorphism is to greenschist facies and contact metamorphism is to hornblende-hornfels facies.The rocks of the Ranger Mine have been subjected to at least two phases of ductile–brittle deformation (D2–D3) and one phase of brittle deformation (D4). These events were preceded by regional diastathermal or extension-related metamorphism (D1) and the development of an ubiquitous bedding-parallel cleavage (S1).D2 resulted in the development of NNE–NNW trending mesoscopic folds (F2) and a network of thrusts and dextral reverse shears. The modelled palaeo-stress directions for the emplacement of pegmatite veins suggests that they formed early in D2. D3 resulted in the development of WNW–NW trending mesoscopic folds (F3), a weakly defined axial planar cleavage (S3) and sinistral reactivation of D2 shears. D2–D3 are correlated with deformation during the Maud Creek Event of the Top End Orogeny (1870–1780 Ma), while the emplacement of granite dykes and pegmatite veins is correlated with emplacement of regional granites at 1870–1860 Ma.D4 is associated with brittle deformation and resulted in the development of normal faults and fault breccias during a period of east–west extension. This event is correlated with regional east–west extension during deposition of Palaeo- to Mesoproterozoic platform sequences.The sequence of tectonic events established in this study indicates that uranium-bearing ore shoots in the Ranger No 1 and 3 pits formed during extension in D4, and after emplacement of the Oenpelli Dolerite at 1690 Ma. However, the currently accepted 1737±20 U–Pb Ma age places the mineralising event at time of regional post-orogenic erosion, after the Top End Orogeny and before emplacement of the Oenpelli Dolerite and extension in D4. The U–Pb age is not consistent with Sm–Nd ages for primary uranium mineralisation at Nabarlek and Jabiluka at 1650 Ma [Econ. Geol. 84 (1989) 64] and does not concur with currently accepted regional tectonic data of Johnston [Johnston, J.D., 1984. Structural evolution of the Pine Creek Inlier and mineralisation therein, Northern Territory, Australia. Unpublished PhD Thesis, Monash University, Australia], Needham et al. [Precambrian Res. 40/41 (1988) 543] and others. Consequently, the absolute age of uranium mineralisation at the Ranger Mine is open.     

http://www.sciencedirect.com/science/article/pii/S1674987115000900

The Chertovo Koryto gold deposit(80 t Au at 1.84 g/t) in the Lena world-class province,Siberia,is hosted in a metamorphosed sequence of the Paleoproterozoic Mikhailovsk Formation that comprises the oldest black shale strata of the Baikal-Patom region.The mineralisation is confined to the thrust zone complicated with a conjugate anticline fold,zones of shearing and dislocation.The struaural position of the mineralisation is similar to that at the giant Sukhoi Log deposit in the neighbouring Mama-Bodaibo zone.In the latter,the isotope age data suggest that Khomolkho black shales,hosts to Sukhoi Log mineralisation,are of Ediacaran age and underwent prograde metamorphism during early Paleozoic.The geochemical composition of the terrigenous rocks that host Sukhoi Log,Chertovo Koryto,and a number of other deposits at the various stratigraphic levels throughout the Proterozoic sequence have much in common.They do not show elevated metal contents above the common black shale abundances,except for Au and As,which is at variance with the accepted view on diagenetic enrichment of black shales in the Lena province.The occurrence of sagenitic rutile in quartz and chlorite pseudomorphs after biotite and other petrographic observations provide evidence on a retrograde nature of the metamorphic mineral assemblages in the Mikhailovsk rocks.The sulphides are pyrrhotite and arsenopyrite with very minor pyrite at Chertovo Koryto,whereas pyrite is the predominant sulphide in the Sukhoi Log ore.Fluid inclusion data on both deposits emphasise a high-temperature nature of the mineralisation albeit revealing great contrast in the fluid composition.Sukhoi Log mineralisation was formed at mixing between low-salinity aqueous solutions and dense gaseous carbonic fluids,which facilitated effective gold scavenging and precipitation,as demonstrated by thermodynamic simulation.The precursory devolatilisation of the Mikhailovsk sediments at the prograde stage results in the paucity of gaseous carbonic fluid during retrograde metamorphism and mineralisation.The similarity in the styles and chemical parameters of mineralisation,and the predominant structural control of ore localisation within the same Precambrian regional tectonic unit support an idea that orogenic gold mineralisation in the Lena province was produced during a single early Paleozoic event.     

Talc mineralisation associated with soft hematite ore, Gongo Soco deposit, Minas Gerais, Brazil: petrography, mineral chemistry and boron-isotope composition of tourmaline

Talc mineralisation occurs as hematite–talc schist between soft hematite ore and dolomitic itabirite at Gongo Soco, Quadrilátero Ferrífero of Minas Gerais, Brazil. The hematite–talc schist and soft hematite have a prominent tectonic foliation of tabular hematite. Tabular hematite without preferential orientation is superimposed on the tectonic foliation. The talcose schist is enriched in F and has a constant Fe/S ratio. Electron-microprobe analyses indicate trace amounts of S in different generations of hematite. The whole-rock Fe/S ratio possibly represents sulfate S from hematite-hosted fluid inclusions. Fluid inclusions in foliation-overprinting hematite and chlorite geothermometry from talcose rocks suggest, respectively, temperatures from <200°C to ~300°C. Tourmaline, a rarely observed mineral in the hematite–talc schist, belongs to the alkali group and falls in the dravite compositional field. Boron-isotope determinations of tourmaline crystals, using secondary ion mass spectrometry, vary from −20‰ to −12‰ δ¹¹B. This compositional isotopic range and the tourmaline chemical composition suggest a meta-evaporitic origin. A non-marine evaporitic setting is the most likely source of acidic, highly oxidising fluids, which resulted in the abundant F-bearing talc and the presence of otherwise immobile Ti in hematite. Oxidising brines were channelled along shear zones and converted dolomitic itabirite into the Gongo Soco soft hematite and the talc mineralisation. The latter is envisaged as the hydrothermal wall-rock alteration of dolomitic itabirite, which gave rise to the soft hematite ore.     

The Syama and Tabakoroni goldfields,Mali

Gold deposits in the Syama and Tabakoroni goldfields in southern Mali occur along a north-northeast trending mineralised litho-structural corridor that trends for approximately 40 km. The deposits are interpreted to have formed during a craton-wide metallogenic event during the Eburnean orogeny. In the Syama goldfield, gold mineralisation in 9 deposits is hosted in the hanging-wall of the Syama-Bananso Shear Zone in basalt, greywacke, argillite, lamprophyre, and black shale. Gold is currently mined primarily from the oxidised-weathered zone of the ore bodies. In the Syama deposit, mineralisation hosted in altered basalt is associated with an intense ankerite–quartz–pyrite stockwork vein systems, whereas disseminated style mineralisation is also present in greywackes. In contrast, the Tellem deposit is hosted in quartz–porphyry rocks.In the Tabakoroni goldfield, gold mineralisation is hosted in quartz veins in tertiary splay shears of the Syama-Bananso Shear Zone. The Tabakoroni orebody is associated with quartz, carbonate and graphite (stylolite) veins, with pyrite and lesser amounts of arsenopyrite. There are four main styles of gold mineralisation including silica-sulphide lodes in carbonaceous fault zones, stylolitic quartz reefs in fault zones, quartz–Fe–carbonate–sulphide lodes in mafic volcanics, and quartz–sulphide stockwork veins in silicified sediments and porphyry dykes. The several deposit styles in the goldfield thus present a number of potential exploration targets spatially associated with the regional Syama-Bananso Shear Zone and generally classified as orogenic shear-hosted gold deposits.     

黑龙江东北部汤原断陷断块体运动特征及其对油气成藏的控制作用

应用构造运动学理论,以地质、地球物理和钻井资料为基础,对汤原断陷基底和各断块体的运动特征进行研究,证实断陷内第Ⅳ块体的基底伸展量最大,第Ⅴ块体的基底伸展量最小;通过对15个块体的实例计算总结出不同构造、不同时期断块体的翘倾运动程度存在很大差异;汤原断陷构造运动控制了油气藏类型。伸展运动和压扭性挤压运动形成构造油气藏,伸展运动早、中期在向斜部位形成岩性油气藏,断块体翘倾运动和抬升剥蚀作用形成地层油气藏。     

德兴大型铜金矿集区构造环境和成矿流体研究进展

江西德兴地区是我国东部成矿带中的大型矿集区之一,集中了铜厂斑岩铜矿、银山多金属矿和金山金矿等大型、超大型矿床。它又处在中国东南部大地构造的关键部位,因此,对德兴大型铜金矿集区的研究始终与该地区的构造背景及演化相伴随。目前对该地区构造格局的认识以NW侧的九岭地体与SE侧的怀玉地体沿赣东北深大断裂带的碰撞拼贴为主流;在这两个地体于晚元古代碰撞拼贴之后,该地区所经历的主要是板内(陆内)的构造活动。德兴大型铜金矿集区的成矿作用与燕山期构造—岩浆活动有着成因上的密切联系,而德兴地区的中元古界地层成矿元素含量较高,不同程度地为本区铜厂、金山、银山等矿床提供了成矿物质。成矿流体的研究成果已表明不同的矿床有不同的流体过程:铜厂斑岩铜矿成矿早阶段以岩浆派生流体为主、而晚阶段(主要成矿阶段)有大气降水的大量参与;银山多金属矿成矿流体主要为大气降水来源;金山金矿的成矿流体则以变质水为重要来源。     

内蒙古莫力达瓦旗哈达阳构造混杂岩地质特征及发现的意义

哈达阳构造混杂岩出露于嫩江黑河构造带之中.根据区域地质背景及构造混杂岩中岩块地质及地球化学特征,划分了基质、原地岩块及异地岩块3部分.基质主要为绿帘黑云绿泥构造片岩.原地岩块主要有绿帘黑云绿泥构造片岩及可能来自海沟外缘缓坡的砾岩.异地岩块主要有角闪石岩、混染闪长岩及变酸性火山岩.角闪石岩及混染闪长岩岩石地球化学特征表明,其形成于与消减作用相关的边缘海扩张环境,而变酸性火山岩具有岛弧钙碱性火山岩特征.上述特征说明,哈达阳构造混杂岩与板块俯冲消减-碰撞作用相关.沿红山梁、哈达阳直达依克特一带出露的古生代地层彼此之间均为断块接触,认为在该沿线存在一条早石炭世末的构造混杂岩带.哈达阳构造混杂岩的发现为正确认识嫩江黑河构造带性质,正确分析构造带结构都具有重要意义.     

印度-欧亚侧向碰撞带构造-岩浆演化的动力学背景与过程——以藏东三江地区构造演化为例

对于印度与欧亚板块的侧向碰撞带,即藏东三江地区的新生代构造分析揭示出三种不同性质的构造样式,它们形成于不同的地质时期,发育于不同的地壳层次：（1）区域规模至露头尺度上发育的具有薄皮属性的逆冲断层与推覆构造,它们广泛分布于三江地区,尤其是兰坪-思茅盆地内;（2）以红河-哀牢山断裂、澜沧江和怒江-高黎贡山断裂等为代表的区域高温型走滑韧性剪切带构造和局部发育的脆性走滑断裂构造,后者在中新生代盆地内部断裂更为发育;（3）遍布全区发育的变质核杂岩构造与地堑-半地堑盆地.区域岩浆活动性与区域构造事件的发生具有密切的时空联系.区域性递进收缩事件与走滑事件发生于碰撞过程的早期阶段,并随后伴随着早期具有岩石圈板块俯冲性质的碰撞弧高钾岩浆活动,而后期的递进伸展事件诱发了板内伸展环境中的晚期高钾岩浆活动.二者之间的碱性岩浆活动间歇期,对应着区域构造体制的转变与区域伸展作用的发生,变质核杂岩的发育与微弱的钙碱性岩浆活动是其最直接的表现.区域古地磁资料分析表明,印度-欧亚板块之间的板块相互作用、区域板块与地块的旋转以及由此所致的不同构造环境制约着各种地质事件的发生与发展.北向运动的印度板块的旋转致使三江地块在新生代演化中发生了两次规模与特点不一的地块旋转过程,即早期的大角度快速旋转和晚期的小角度慢速旋转事件.它们分别对应于早期的递进收缩变形、走滑事件和具有碰撞弧属性的碱性岩浆活动与中期的区域伸展、变质核杂岩的发育与微弱的钙碱性岩浆活动性,以及后期的递进伸展作用和晚期陆内碱性岩浆活动性.     

阜康矿区西部构造运动作用下煤储层渗透率分布特征

查明小范围内煤储层渗透率分布特征,可为合理井网部署、科学预测煤层气产能提供重要保障。对新疆阜康矿区西部煤岩层节理进行观测、统计和配套,获得了燕山晚期、喜马拉雅早期和喜马拉雅晚期3期构造应力场的主方向。结合构造运动反演法和煤层受力差异得出了研究区多期构造运动作用后14个块段内煤体结构及煤层的渗透率分布特征。结果表明:受多期构造运动作用影响,小范围内A₂煤储层渗透率非均质性强,位于向斜核部扬起端埋深较浅处的煤层,煤体结构以碎裂-原生结构煤为主,渗透性最好;东北部风氧化带以深及南翼块段,煤层变形较弱,煤层渗透率中等;向斜核部埋深较深部位受多期构造运动影响较大,煤体变形较严重,以碎粒-糜棱煤为主,渗透性差;南部及西北部,受多期构造运动作用影响最大,煤层渗透性最差。钻井取心及渗透率实测资料验证了预测结果的准确性,此研究方法为多期构造影响下的小范围内煤层渗透率预测提供了一种思路和借鉴。      

Characteristic features of salt tectonics offshore North Sinai, Egypt

Salt tectonic along offshore North Sinai was studied using seismic reflection data. The study revealed and identified various types of salt tectonics and structures in the study area. The triggering mechanism of salt tectonics was attributed to the pressure regime initiated from overloading sediments on the Messinian evaporites. The sediment load of 3,000?m exceeds the critical load (more than 1,000?m) and hence creates a pressure zone. The salt-generated structures resulted from thin-skinned extension that is driven by gravity gliding of the overloading sediments above the Messinian evaporite boundary, which acts as a detachment layer. These structures comprise normal growth faults and keystone grabens, trending roughly perpendicular to the slope of the continental margin. Salt tectonics in the study area were also triggered by the deformation of the movement of evaporite layer that causes stretching and fragmentation of the evaporite layer. Moving salt layer took place laterally and vertically, causing lateral and vertical pressures inside the Pliocene sediments. These movements of sediments led to the formation of salt rollers, salt weld, salt diapirs, rollover structures, and fault blocks. The interpretation of seismic data illustrates that the evaporite layer was switched off between the famous reflector M at its top and another reflector N at its base. M reflector is present and can be traced across the whole study area, while the N reflector pinched out in some parts of the study area.     

Contrasting coeval paragenesis of gold and scheelite in an orogenic hydrothermal system,Macraes mine,New Zealand

The Macraes deposit (> 10 Moz resource) is a Cretaceous orogenic system hosted in the Hyde-Macraes Shear Zone (HMSZ) which was mineralised under lower greenschist facies during later stages of lower greenschist facies metamorphism of host metasedimentary schists. Gold is encapsulated primarily in sulphides that have replaced silicates in ductile shears that are focussed in micaceous rocks. The shears anastomose around structurally competent lenses, and were enhanced by hydrothermal graphite deposition and alteration of albite to muscovite. In contrast, scheelite with minor auriferous sulphides occurs in multigenerational quartz veins that filled fractures in competent lithologies. Hence, scheelite was deposited coevally with gold, from the same hydrothermal fluid, but in different structural settings from most gold at all scales from millimetres to hundreds of metres. Consequentially, there is weak correlation between Au and W at all scales in the deposit. Multigenerational gold and scheelite mineralisation occurred during progressive deformation in the shear zone in two contrasting structural and mineralogical styles in syn-deformationally weakening gold-bearing micaceous shears, and in syn-deformationally hardened competent rocks that became silicified and veined with quartz and scheelite. Hydrothermal fluid flow in the gold-bearing shears occurred at the grain boundary, microshear, and microfracture scales, and was slow (< 1 m/year), continuous, and pervasive. In contrast, vein formation in more competent lithologies was episodic, locally rapid (> hundreds of m/year), and was controlled by fracture permeability. The Au and W enrichment in the Macraes deposit resulted from regional scale metal mobility, driven by coeval recrystallisation in higher-grade (upper greenschist to amphibolite facies) metamorphism that persisted structurally below the Macraes deposit for at least 10 Ma after mineralisation ceased.     

Thrust-controlled gold mineralisation at the Elandshoogte Mine,Sabie-Pilgrim's Rest goldfield,South Africa

Stratiform quartz-sulphide-gold veins, locally termed reefs are hosted within the Proterozoic Transvaal Sequence sedimentary succession, in the Sabie-Pilgrim's Rest goldfield, eastern Transvaal. These deposits have produced about 180 tonnes of gold and share many characteristics with those of Telfer, Western Australia. Detailed examination of the Elandshoogte Mine shows that gold deposition occurred in two stages, both linked to bedding-parallel thrust faulting within the sedimentary pile. Deformation being concentrated within incompetent shale beds, interlayered within more competent units. The majority of gold was introduced in the second stage of mineralisation and occurs within fractures in early-formed sulphide minerals. Deposition of competent quartz veins accompanying early sulphide and gold mineralisation resulted in a change in deformation style within the reef zone, from early shearing in shales to later duplex faulting of the quartz-reef. Fluids accompanying faulting are implied to have transported gold, and a magmatic source of mineralisation is suggested.     

湘中南大庙口地区构造变形特征及其对区域页岩气构造保存条件的启示

近几年来对湖南省页岩气地质条件进行了大量调查研究,但对页岩气的构造保存条件研究和评价很少,因而影响了区域页岩气勘查工作的科学部署。笔者在湘中南永州凹陷西北缘的水岭-大庙口地区开展了1∶50 000页岩气地质调查,对该地区构造特征和构造演化过程进行了研究,在此基础上探讨了页岩气保存和富集的构造条件。调查区构造变形强烈,主要构造类型有：上古生界盖层中发育的NNW-近SN向（主）褶皱和EW向（次）褶皱,下古生界中发育的NNE向和NE向膝折,切割上古生界和下古生界的NNW-SN向、NE向、NW向等3组断裂（主要为逆断裂、正断裂,少量为走滑断裂）,下古生界中极为发育的NNW向板劈理以及泥盆系跳马涧组中发育的SN向、NNE向破劈理等。结合区域构造背景,初步确定上述构造主要形成于早古生代以来的8期构造变形事件,其中以加里东运动、印支运动和早燕山运动的挤压事件以及白垩纪区域伸展事件等最为重要。奥陶系烟溪组和天马山组底部的黑色页岩为调查区页岩气勘探目标层,但钻孔岩心页岩气解吸实验表明含气性极差。分析认为,多期构造运动造成的抬升和剥蚀及形成的断裂、劈理,既导致页岩气的散逸,也使得目标层仅局部有保存;多期构造运动形成的复杂构造样式,使得上古生界之下目标层的空间展布特征难以探明;加里东运动和印支运动所诱发花岗质岩浆活动相关的高地热场区会显著增高有机质热演化程度,总体不利于页岩气的保存。调查区对页岩气富集和保存不利的构造条件基本适用于永州凹陷及周缘其它地区,因此认为永州凹陷及周缘页岩气成藏潜力非常有限。本研究成果对区域页岩气成藏条件的客观认识以及页岩气勘查工作的合理部署具有重要的启示意义。     

Ocean Plate Stratigraphy in East and Southeast Asia

Ancient accretionary wedges have been recognised by the presence of glaucophane schist, radiolarian chert and mélange. Recent techniques for the reconstruction of disrupted fragments of such wedges by means of radiolarian biostratigraphy, provide a more comprehensive history of ocean plate subduction and successive accretion of ocean floor materials from the oceanic plate through offscraping and underplating.Reconstructed ocean floor sequences found in ancient accretionary complexes in Japan comprise, from oldest to youngest, pillow basalt, limestone, radiolarian chert, siliceous shale, and shale and sandstone. Similar lithologies also occur in the mélange complexes of the Philippines, Indonesia, Thailand and other regions. This succession is called ‘Ocean Plate Stratigraphy’ (OPS), and it represents the following sequence of processes: birth of the oceanic plate at the oceanic ridge; formation of volcanic islands near the ridge, covered by calcareous reefs; sedimentation of calcilutite on the flanks of the volcanic islands where radiolarian chert is also deposited; deposition of radiolarian skeletons on the oceanic plate in a pelagic setting, and sedimentary mixing of radiolarian remains and detrital grains to form siliceous shale in a hemipelagic setting; and sedimentation of coarse-grained sandstone and shale at or near the trench of the convergent margin.Radiolarian biostratigraphy of detrital sedimentary rocks provides information on the time and duration of ocean plate subduction. The ages of detrital sediments becomes younger oceanward as younger packages of OPS are scraped off the downgoing plate.OPS reconstructed from ancient accretionary complexes give us the age of subduction and accretion, direction of subduction, and ancient tectonic environments and is an important key to understanding the paleoenvironment and history of the paleo-oceans now represented only in suture zones and orogenic belts.     

黑龙江东北部汤原断陷断块体运动特征及其对油气成藏的控制作用

应用构造运动学理论,以地质、地球物理和钻井资料为基础,对汤原断陷基底和各断块体的运动特征进行研究,证实断陷内第Ⅳ块体的基底伸展量最大,第Ⅴ块体的基底伸展量最小;通过对15个块体的实例计算总结出不同构造、不同时期断块体的翘倾运动程度存在很大差异;汤原断陷构造运动控制了油气藏类型.伸展运动和压扭性挤压运动形成构造油气藏,伸展运动早、中期在向斜部位形成岩性油气藏,断块体翘倾运动和抬升剥蚀作用形成地层油气藏.     

甘肃白银厂矿区及外围区域地质背景、成矿系列及找矿潜力

白银厂矿区及外围是北祁连铜多金属成矿带的主要地段.新元古代以来的大陆裂谷作用-活动陆缘的洋壳俯冲、弧后扩张-陆-陆碰撞造山作用,及其所导致的强烈多期次的火山活动、岩浆侵入及变质作用,为本区提供了优越的成矿条件.区内既有与岛弧海相酸性火山作用有关的白银厂黑矿型Cu-Pb-Zn-Au-Ag成矿系列,又有与弧后扩张脊蛇绿岩套和基性火山岩有关的塞浦露斯型Cu-Zn(Co)系列;与大陆裂陷火山作用有关的喷流沉积型Fe-Cu-Zn-Pb系列以及陆内造山早期与韧-脆性剪切作用有关的Au-Pb系列和与酸性岩浆作用有关的Au-Cu系列等.石青硐-白银厂火山岩带是本区最有找矿潜力、也是快速实现找矿突破的首选区带;朵家滩-白银南-青城皋兰群变质火山岩带,是值得探索的大型喷流沉积型Fe-Cu-Zn-Pb矿床远景区;老虎山-银洞沟-崛吴山火山岩带的塞浦露斯型Cu-Zn(Co)矿床具有扩大资源量和进一步发现矿床的前景;韧-脆性剪切带型Au矿床及与酸性侵入体有关的岩浆期后热液型Au-Cu矿床是两个具有重要意义的找矿新方向.     

坦桑尼亚恩泽加绿岩带玛汀杰金矿地质特征及成因初析

通过对坦桑尼亚恩泽加绿岩带玛汀杰金成矿区的4个金矿（化）体的成矿背景和地质特征进行分析,初步了解该区金矿体地质特征及矿床成因。玛汀杰金矿为产自韧性剪切带的石英脉型金矿,赋矿层位为太古代尼安兹超群绿片岩,矿体由NW向和EW向两组构造控制,矿石类型包括石英脉型、蚀变岩型和构造角砾岩型。普遍发育黄铁绢英云化。矿石w（Au）=0.62×10^-6~3.04×10^-6,部分矿石w（Au）值大于100×10^-6。玛汀杰地区金矿为典型的产自绿岩带韧性剪切带的石英脉型金矿,矿床成因为热液成因。