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J. S. Laberg M. Strasser T. M. Alves S. Gao K. Kawamura A. Kopf G. F. Moore 《Landslides》2017,14(3):849-860
The processes of flow deformation of marine mass-transport sediments, including their ability to affect the underlying substrate and add mass during sediment flow events, are addressed based on sedimentological analyses of strata from the distal part of a ～61-m-thick mass-transport deposit (MTD 6) drilled during Integrated Ocean Drilling Program (IODP) Expedition 333. Our analyses, supported by 3D seismic data, show a cohesive density flow deformed by folding, faulting and shear, except for its lowermost part (～7 m), where no deformation and sediment entrainment was identified. While the lowermost part moved as rigid sediment, the underlying sand layer acted as the basal shear zone for this part of the distal MTD 6. This shear zone was restricted to the sand, not involving the overlying sediments. From this, the studied part of MTD 6 was found to represent a case where the flow behaviour at least partly depended on the location and properties of the underlying sand layer, a situation that so far has received little attention in studies of marine flows. Our results also show that shear-induced mixing, located by the initial layering, is an important process in the flow transformation from cohesive slumps to mud flows and that this may occur over short distances (<4 km) without involving disintegration into blocks, probably due to only moderate prefailure consolidation of the sediments involved. In conclusion, we find that the bulk part of the flow was self-contained from a mass balance point of view and that that the overall amount of entrainment was limited. 相似文献
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The ductile shear zone-type gold deposit is a kind that both the ore-forming mechanism and ore-controlling factors are closely related to the ductile shear zone and its evolution. Ductile shear zone develops in Beishan area, Gansu of Northwest China, and develops especially well in the south belt. The controls of the ductile shear zone on gold deposits are as follows. (1) The regional distribution of gold deposits (and gold spots) is controlled by the ductile shear zone. (2) The ductile-brittle shear zone is formed in the evolution process of ductile shear zone and both are only ore-bearing structures and con- trol the shape, attitude, scale, and distribution of mineralization zones and ore-bodies. (3) Com- presso-shear ductile deformation results in that the main kind of gold mineralization is altered mylonite type and the main alteralization is metasomatic. (4) Ore-bearing fracture systems are mainly P-type ones, some D-type and R-type ones, but only individual R’-type and T-type ones. (5) Dynamic differen- tiation and dynamic metamorphic hydrothermal solution resulting from ductile deformation is one of the sources of ore-forming fluid of gold mineralization, and this is identical with that ore-forming ma- terials are mainly from metamorphic rocks, and ore-forming fluid is mainly composed of metamorphic water, and with the fluid inclusion and geo-chemical characteristics of the deposit. (6) There is a nega- tive correlation between the gold abundance and susceptibility anisotropy (P) of the altered mylonite samples from the deposit, which shows that the gold mineralization is slightly later than the structural deformation. All above further expound the ore-forming model of the ductile shear zone type of gold deposits. 相似文献
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东昆仑大干沟一带铜金锑矿特征及找矿意义 总被引：1，自引：1，他引：0
东昆仑地区处于中朝、塔里木-柴达木、扬子和印度板块的拼合部位,元古宙以来经历了多期次的裂解和拼合。该区以Au、Co、Cu、Pb、Zn、Hg、Sb、As元素组合为特征,其中多处已证实为矿致异常,共发现矿床、矿点等198处,初步显示了良好的找矿前景。目前在大干沟一带已发现铜多金属矿化带一条、金锑含矿构造蚀变带一条。矿化特征基本一致,均赋存于中三叠统闹仓坚沟组北西西向脆韧性剪切带内及两侧的灰白-烟灰色方解石石英脉内,且具有南侧金锑矿化、北侧铜多金属矿化的分带特征。 相似文献
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《Sedimentology》2018,65(4):1067-1096
Submarine landslides, including the basal shear surfaces along which they fail, and their subsequent infill, are commonly observed in modern seabed and seismic reflection data sets; their resultant relief impacts sediment routing and storage patterns on continental margins. Here, three stacked submarine landslides are documented from the Permian Ecca Group, Laingsburg depocentre, Karoo Basin, South Africa, including two superimposed lateral margins. The stratigraphic framework includes measured sections and correlated surfaces along a 3 km long, 150 m high outcrop. Two stacked 2·0 to 4·5 km wide and 90 m and 60 m deep erosion surfaces are recognized, with lateral gradients of 8° and 4°, respectively. The aim of this study was to understand the evolution of a submarine landslide complex, including: evolution of basal shear surfaces/zones; variation of infill confinement; and location of the submarine landslides in the context of basin‐scale sedimentation and degradation rates. Three stages of formation are identified: (i) failure of submarine landslide 1, with deposition of unconfined remobilized deposits; (ii) failure of submarine landslide 2, forming basal shear surface/zone 1, with infill of remobilized deposits and weakly confined turbidites; and (iii) failure of submarine landslide 3, forming basal shear surface/zone 2, with infill of remobilized deposits and confined turbidites, transitioning stratigraphically to unconfined deposits. The expression of basal shear varies laterally, from metres thick zones in silt‐rich strata to sharp stepped surfaces in sand‐rich strata. Faulting and rotation of overlying bedding suggest that the shear surfaces/zones were dynamic. Stacking of landslides resulted from multi‐phase slope failure, increasing down‐dip topography and confinement of infilling deposits. The failure slope was probably a low supply tilted basin margin evidenced by megaclast entrainment from underlying basin‐floor successions and the lack of channel systems. This study develops a generic model of landslide infill, as a function of sedimentation and degradation rates, which can be applied globally. 相似文献
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Meru volcano is located within the Northern Tanzanian Divergence Zone where the east branch of the East African Rift splits into several branches. The 4565-m-high Meru volcano is breached on the east flank by a horseshoe-shaped scar following a major collapse associated with the Momella debris avalanche approximately 9000 years ago. Remote sensing combined with detailed field mapping allowed the characterisation of the Momella debris avalanche deposit, structure, and texture. Hummocks, ridges, lineaments, lobes, grabens and shear zones are observed on the surface of the deposit. The most common facies observed are the mixed facies with indurated and shattered outcrops and the matrix facies. The collapse involved a volume of 20 ± 2 km3 with a deposit that spread over an area of 1250 km2, up to the base of Kilimanjaro. Based on field evidence, we suggest that water played a key role in the deformation, facies formation, avalanche emplacement and mobility of the entire deposit but to a lesser extent south of Ngurodoto complex. The deformation and emplacement of the avalanche were accommodated by both extension and shearing on a water-fluidised basal layer. 相似文献
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新疆北部阿尔泰地区金矿床发育.根据金矿床在成矿作用、主要控矿因素、矿石建造和组构、容矿岩石建造等方面的特征划分为2种金矿类型：造山带型金矿床和浅成低温热液金矿床.2种类型金矿床具有不同的矿化特征,受不同的构造类型控制.浅成低温热液金矿床受火山构造及脆性断裂控制,可进一步划为2种亚类型：高硫型和低硫型.造山带型金矿受韧性剪切带控制,也可划为2种亚类型：一为石英脉型,另一种为蚀变岩（糜棱岩）型.区内金矿床形成于3个时期：高硫型浅成低温热液金矿床形成于石炭纪,造山带型金矿床形成于二叠纪,低硫型浅成低温热液金矿床形成于中生代,并分别对应于海西期碰撞造山阶段、后碰撞造山阶段及中生代稳定陆块发育的地球动力学环境. 相似文献
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韧性剪切带型金矿是一种成矿机制与控矿因素都与韧性剪切带及其演化密切相关的金矿床类型。阿尔金北缘地区不同层次剪切带发育,金矿床受韧性剪切带控制明显,在区域上,韧性剪切带控制金矿床(点)的分布;在矿床范围内,韧性剪切带及其演化过程中形成的韧脆性剪切带既是唯一的赋(含)矿构造,也对矿化带、矿体的形态、产状、规模及分布起决定性的控制作用;压扭性韧性剪切变形特点决定了金矿化类型以蚀变糜棱岩型为主,交代蚀变作用发育。含矿构造裂隙以P型为主,少量D型和R型,个别为R~1型和T型;构造变形所引发的动力分异作用及其形成的动力变质热液是金矿成矿流体的主要来源之一,这与地球化学和成矿流体包裹体研究显示的大平沟金矿床成矿物质主要来源于变质岩、成矿流体有相当部分来源于变质水的特征相吻合。结合糜棱岩磁组构研究,发现磁各向异性度P值与金元素含量呈负相关关系,说明构造变形早于金矿化蚀变作用,这种时序关系进一步佐证了韧性剪切带型金矿床的成矿模式。即大面积的韧性变形构造动力分异作用形成的含金热液不是就地原位矿化,而是向上迁移并集中到范围比较窄小的韧-脆性或脆性裂隙中才发生金元素富集,最终形成金矿床。 相似文献
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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。 相似文献
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Olivier Rabeau Jean-Jacques Royer Michel Jébrak Alain Cheilletz 《Mineralium Deposita》2013,48(7):817-824
The location of potentially unrecognized gold deposits in the close vicinity of the Cadillac–Larder Lake Fault Zone in the Archean Abitibi Subprovince (Canada) is predicted by applying a stochastic approach to the distribution of known gold deposits. The methodology uses the distances between neighboring orogenic gold deposits along the fault trace. The cumulative distribution of the curvilinear inter-distances along the fault zone, are adequately represented by a log-uniform model. The average inter-distance is 1.95 km, and an upper inter-distance of 5.6 km is observed. The same distribution pattern appears along the Destor–Porcupine Fault Zone (Abitibi). This log-uniform distribution shows that the spatial distribution of gold deposits is regionally controlled by the major crustal shear zone. Lithologies and structures only seem to exert a local influence at the deposit scale. The log-uniform spacing could be interpreted as the result of the crustal failure locations induced by hydraulic overpressure along mechanically independent segments on the main fault. 相似文献
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阿尔金北缘红柳沟-拉配泉一带铜金矿床硫同位素特征及其意义 总被引：3，自引：0，他引：3
通过对阿尔金北缘地区铜金矿床的硫同位素研究, 结合矿床地质特征, 划分了区内矿床的成因类型, 认为主要有3类:似层状海相火山沉积型铜多金属矿床、韧性剪切带型(铜)金矿床、受裂隙控制的脉状岩浆热液型铜多金属矿床。结合区域构造演化特点, 探讨了矿床成因类型与区域构造演化阶段的关系, 认为区域成矿作用可分为3个阶段:第一阶段为早古生代早中期板块构造海底扩张作用时期, 形成以喀腊大湾为代表的海相火山沉积型铜多金属矿床; 第二阶段是早古生代晚期板块构造聚合碰撞作用时期, 形成以大平沟和红柳沟为代表的韧性剪切带型(动力变质热液型)(铜)金矿床; 第三阶段是早古生代末板块构造碰撞后的岩浆活动和偏脆性断裂构造活动时期, 形成以索尔库里北山和拉配泉为代表的受裂隙控制的岩浆热液型铜多金属矿床。从硫同位素特征、矿床成因类型及其与区域构造演化的关系上分析, 该区具有较好的铜金多金属矿床找矿远景。 相似文献
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浙江诸暨璜山金矿构造特征及深部找矿预测 总被引：1，自引：0，他引：1
诸暨璜山金矿是浙江省著名的金矿之一,位于江山-绍兴断裂带北东段。本文通过对璜山金矿和庙下畈金矿的构造特征进行对比研究,认为这两个金矿形成的构造背景和成矿时代基本相同,但矿体走向和剪切动向截然不同,璜山金矿赋存于NE走向的剪切带内,庙下畈金矿位于NW走向的剪切带内,二者构成共轭剪切带,叠加在江山-绍兴主干韧性剪切带之上。成矿后该区先后受到NW-SE和NNE-SSW方向的挤压,形成NW走向和近SN方向的脆性断裂,对矿体起到破坏作用。依据共轭剪切带的空间分布,推测江绍断裂南东侧可能存在与璜山金矿对应的赋矿剪切带,该带位于新元古代陈蔡群变质岩之下,埋藏较深,是璜山地区深部找矿的有利勘探区。 相似文献
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通过野外观察,在南川地区铝土矿含矿岩系中识别出一层底砾岩和一层分流河道沉积,结合岩性特征和B、Sr、Ba、Ga、Rb、MnO、TiO2等的地球化学特征,对南川地区铝土矿含矿岩系的沉积相进行了划分。认为南川地区铝土矿形成于中二叠世海侵过程中的陆缘近海湖环境,为沉积型铝土矿床。． 相似文献
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新疆鄯善县康古尔金矿带小尖山金矿位于星星峡谷带—旱山微板块中的雅满苏-红石山-黑鹰山晚古生代陆内裂谷带内康古尔金矿带的东部,产于苦水大断裂南侧的巨型韧性剪切带内,具有明显韧性剪切带控矿作用。矿体分为2类:蚀变岩型金矿、石英脉型金矿。矿区初步圈定了3条较具规模的蚀变岩型金矿体和2条石英脉型金矿体。其中,蚀变岩型金矿是主要矿床类型,赋存于安山质凝灰岩与英安质凝灰岩的接触带上安山质凝灰岩一侧,整个矿带受苦水断裂之次级韧性剪切带控制。通过综合分析,初步认为该区金矿属于与韧性剪切带有关的中—低温热液型金矿床,并总结了控矿构造、容矿岩石、岩浆岩、地球化学、热液蚀变等5个方面的找矿标志。 相似文献
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漠滨脆—韧性剪切带型金矿床控矿构造研究 总被引：4，自引：0，他引：4
层间右旋逆冲脆—韧性剪切带构造控制漠滨金矿床。剪切带变形过程经历了早、中、晚3个阶段。而金矿化的形成和富集又与剪切带多阶段的演化密切相关,金矿化是剪切构造作用形成的。因此,剪切带既是控矿因素,又是重要的成矿机制,属层间逆冲脆—韧性剪切带型金矿床。 相似文献
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There may be many as-yet-undiscovered porphyry copper deposits that exist as blind deposits deep within exposed rock bodies. The Kalamazoo porphyry copper-molybdenum deposit is a blind deposit present at depths up to at least 1,000 m (about 3,200 ft) that contains zoning features common to many of the known porphyry copper deposits found in western North and South America.As the preliminary phase in a geochemical study of the Kalamazoo deposit, whole-rock samples of core and cuttings from two drill holes have been analyzed for 60 different elements. Each hole represents a different major rock unit and each has penetrated completely through all the existing alteration zones and the ore zone.Plots of concentration vs. depth for 17 selected elements show distinct high- or low-concentration zones that are spatially related to the ore zone. For most of the ore-related elements no significant correlation with the two lithologies is apparent. The spatial distribution and abundance of elements such as Co, Cu, S, Se, Mn, Tl, Rb, Zn, B, and Li may be useful in determining the direction for exploration to proceed to locate a blind deposit. Trace element studies should be valuable in evaluating areas containing extensive outcrops of rocks with disseminated pyrite. Elemental zoning should be at least as useful as alteration-mineralization zoning for evaluating rock bodies thought to contain blind deposits similar to the Kalamazoo deposit. 相似文献
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西天山地区金矿床主要成因类型及找矿方向 总被引：13，自引：4，他引：13
西天山地区地处古亚洲构造域天山-兴蒙成矿带的西段，经历了漫长复杂的构造演化过程，尤其是海西期强烈的构造岩浆活动，为金成矿创造了有利的条件．近几年，本区找金工作取得了突破性的进展，相继发现了阿希、望峰、大山口等金矿床，显示了良好找金前景．根据前人和笔工作，讨论了本区主要金矿化类型浅成低温热液型(又进一步划分为冰长石-绢云母型和硅化岩型)斑岩型、韧性剪切带型穆龙套型等的成矿特征，在综合分析基础上，指出找矿方向． 相似文献
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康古尔塔格韧性剪切带是金矿重要控矿带,产有康古尔、马头滩、石英滩等重要矿床。野马泉西金矿即位于该韧性剪切带的东延苦水-雅满苏韧性剪切带上,属韧性剪切带控矿型金矿。本文在野外地质调查基础上采集了野马泉西金矿探矿工程坐标、工程内样品的分析测试成果等数据,采用地质块段法对野马泉西金矿资源量进行了估算,形成了数据集。数据集测试样品均委托有国家甲级资质的测试中心进行,内外检合格率90%以上,数据质量可靠,对周边同类型矿床的资源量估算具参考意义。 相似文献