滇西墨江金厂金矿床时空四维结构模型

对墨江金厂金矿关键性地质问题研究结果表明,矿区金厂韧性剪切带（ＳＺｊｃ）、ＮＷＷ向褶皱构造和金矿超镁铁岩体侵位构造是不同成矿期的控矿构造,金矿床有三种成因类型,分别对应三期三种不同类型的成矿作用。     

Petrogeochemical typification of the ultramafic rocks from the Idar greenstone belt,Kan block,East Sayan

The ultramafic rocks of the Kan block, East Sayan, are confined mainly to the Idar greenstone belt. In terms of formational affiliation, they are subdivided into two groups: magmatic (Kingash Complex) and residual (Idar Complex) ones. The magmatic ultramafic rocks compose hypabyssal and subvolcanic bodies, which are represented by rocks of dunite-wehrlite-picrite association with cumulate textures. Uninterrupted chemical variations of the magmatic ultramafic rocks indicate subsequent magmatic differentiation of parental picritic melt in the intermediate deep-seated chambers and emplacement of its derivatives in the crystallization site. Differentiation leads to proportional increase of all rare-earth and other incompatible elements. The residual ultramafics occur as boudined dunite-harzburgite bodies showing metamorphic granoblastic textures. They have more homogenous chemical composition close to those of ophiolite complexes, which represent strongly depleted mantle rocks brought to the upper lithospheric levels via deep-seated thrusts. Residual ultramafics differ from magmatic rocks in notably lower contents of some trace and rare earth elements.     

Structural controls on orogenic gold mineralisation in the Klondike goldfield,Canada

The Klondike Schist that forms the basement rocks for the famous Klondike placer goldfield was emplaced as km-scale thrust slices in Early Jurassic time, along with some thin (10 to 30 m-scale) slices of greenstone and ultramafic rocks. Permian metamorphic fabrics in the schists were deformed during thrust emplacement by structures formed as the rocks passed through the brittle–ductile transition. Early-formed thrust-related structures were almost-pervasive recumbent folds that affected both the schist and greenstone/ultramafic slices and imposed a spaced cleavage with minor recrystallisation of micas. These structures gave way to shallow-dipping phacoidal cleavage near (within <100 m of) thrust structures. Thrust-related structures have been overprinted locally by well-defined steeply dipping reverse fault-fold zones, and associated upright folding on regional (km) to mesoscopic (m) scales. The fold-fault zones occur as two orthogonal sets of structures oriented NW to N and NE to E. Some of these steeply dipping fault zones have been reactivated by Late Cretaceous normal faulting. Orogenic (mesothermal) gold-bearing veins were emplaced in local sites of extension during or after formation of the compressional fault-fold zones and before normal fault reactivation. Over 400 veins (m to cm-scale) observed in this study imply a general NW strike for mineralised structures (W to N), but with a broad scatter of orientations. Vein emplacement was controlled principally by fold axial surfaces of kink folds of the fault-fold generation. However, some other local extension sites have opened along preexisting structures to host veins locally, including metamorphic foliation and spaced cleavage planes. In addition, irregular extensional fractures with no obvious structural control host some veins. The Klondike mineralised veins formed as swarms with broad regional structural control, but represent relatively diffuse mineralised zones, with numerous scattered small veins, compared to most orogenic vein systems. These diffuse vein swarms appear to be sufficient sources for the rich and geographically localised placer gold deposits that formed in overlying gravels during erosion of the Klondike Schist basement.     

Geology and structural history of the southwest Precordillera margin, northern Mendoza Province, Argentina

Rocks and structures in the southwest Precordillera terrane, located in western Argentina, constrain the Paleozoic distribution of continents and the development of the western margin of Gondwana. Detailed mapping of an area in the southwest Precordillera allowed identification of several pre-Carboniferous rock units formed in distinct tectonic environments and were later tectonically juxtaposed. The pre-Carboniferous rock units comprise carbonate metasiltstone, metasandstone, massive diabase, and quartzo-feldspathic gneiss intruded by ultramafic rocks and layered gabbro. Preliminary structural analysis indicates that the present distribution of units is due to two contractional deformation episodes, an east-directed Devonian ductile event and a west-directed Tertiary brittle event. The metasedimentary rocks, which form the structural base of the area and are part of the western Precordilleran passive margin sequence, were juxtaposed along minor ductile shear zones early in the ductile event. Their contact was then folded during continued ductile deformation; at this time the ultramafic/layered gabbro complex and the massive diabase were emplaced over the metasedimentary units along narrow ductile shear zones. Brittle deformation, associated with the Andean orogeny, involved open folding, thrust faulting, and reactivation of some ductile features.     

A preliminary study of komatiites in Anshan-Benxi-Fushun region,Northeast China

Discovered for the first time in the Lower Anshan Group with a metamorphic grade from amphibolite to granulite facies, komatiites occur as bedded ultramafic volcanic rocks on the ocean-floor. The komatiites in the Anshan-Benxi-Fushun region occurring in the metamorphic rocks are some monomineralic rocks such as hornblendite, clinopyroxene and hypersthenite. Local komatiites are found retaining some typical pre-existing structures and textures of volcanic rocks, such as blastovariolitic and blastodoleritic textures. The chemical composition of komatiites in this region is much similar to that of other well-known model komatiites in the world, and so are their geochemical characteristics. The occurrence of komatiites in the Anshan-Benxi-Fushun region provides strong evidence showing that this region is an Archean greenstone belt. Studies on komatiites in this region will shed much light on the stratigraphic division of the Anshan Group and the paleo-structure of the greenstone belt as well as on the rules governing metallogenesis in the Anshan-Benxi-Fushun region.     

Airborne gamma-ray and magnetic anomaly signatures of serpentinite in relation to soil geochemistry, northern California

Serpentinized ultramafic rocks and associated soils in northern California are characterized by high concentrations of Cr and Ni, low levels of radioelements (K, Th, and U) and high amounts of ferrimagnetic minerals (primarily magnetite). Geophysical attributes over ultramafic rocks, which include airborne gamma-ray and magnetic anomaly data, are quantified and provide indirect measurements on the relative abundance of radioelements and magnetic minerals, respectively. Attributes are defined through a statistical modeling approach and the results are portrayed as probabilities in chart and map form. Two predictive models are presented, including one derived from the aeromagnetic anomaly data and one from a combination of the airborne K, Th and U gamma-ray data. Both models distinguish preferential values within the aerogeophysical data that coincide with mapped and potentially unmapped ultramafic rocks. The magnetic predictive model shows positive probabilities associated with magnetic anomaly highs and, to a lesser degree, anomaly lows, which accurately locate many known ultramafic outcrops, but more interestingly, locate potentially unmapped ultramafic rocks, possible extensions of ultramafic bodies that dip into the shallow subsurface, as well as prospective buried ultramafic rocks. The airborne radiometric model shows positive probabilities in association with anomalously low gamma radiation measurements over ultramafic rock, which is similar to that produced by gabbro, metavolcanic rock, and water bodies. All of these features share the characteristic of being depleted in K, Th and U. Gabbro is the only rock type in the study area that shares similar magnetic properties with the ultramafic rock. The aerogeophysical model results are compared to the distribution of ultramafic outcrops and to Cr, Ni, K, Th and U concentrations and magnetic susceptibility measurements from soil samples. Analysis of the soil data indicates high positive correlation between magnetic susceptibilities and concentration of Cr and Ni. Although the study focused on characterizing the geophysical properties of ultramafic rocks and associated soils, it has also yielded information on other rock types in addition to ultramafic rocks, which can also locally host naturally-occurring asbestos; specifically, gabbro and metavolcanic rocks.     

Petrogenesis of ultramafic and mafic rocks of the Thompson Nickel Belt,Manitoba

Abundant sill-like bodies of serpentinized ultramafic rocks, with associated nickel sulfide deposits, are found on the western side of the Thompson Nickel Belt near the Moak Lake-Setting Lake cataclastic fault zone. The ultramafic rocks range in composition from dunite to orthopyroxenite and feature variable alteration. Chemical variation across the bodies is suggestive of in-situ differentiation controlled mainly by olivine and orthopyroxene. Relative abundances of some elements, incompatible for olivine and orthopyroxene, suggest a parental liquid of komatiitic affinity. Ultramafic and mafic rocks are petrogenetically linked. A high degree of partial melting of mantle material and subsequent low-pressure crystal fractionation are responsible for the spectrum of composition from ultramafic to mafic.Publication 19-84, Ottawa-Carleton Centre for Geoscience Studies     

贵州白层超基性岩对右江盆地燕山晚期拉张环境深源岩浆演化作用的启示——来自地球化学的证据

白层超基性岩产出于扬子地台西南缘,该区域存在多期次的岩浆活动,出露多处超基性岩体。对白层11件超基性岩样品进行了主量和微量元素（包括稀土元素）及铂族元素分析,结果表明,白层超基性岩主量元素变化范围不大,具低钠富钾钙碱性岩石的地球化学特征;该超基性岩富集Ba、Sr、Rb等大离子亲石元素及Nb等高场强元素;稀土元素总量高,球粒陨石标准化曲线呈强烈的右倾趋势,轻、重稀土元素分馏明显,Eu、Ce异常不明显;铂族元素总含量低,且分异不明显。该超基性岩的地球化学特征显示,其形成于燕山晚期右江盆地大规模岩石圈伸展减薄的构造背景下;岩浆来源于低程度部分熔融的超镁铁质地幔,石榴子石及硫化物在熔融过程中残留于源区。岩浆在上升过程中未发生明显的地壳物质混染。岩浆结晶分异程度不高,发生了橄榄石与单斜辉石的结晶分异但未发生斜长石的分离。     

西藏松多地区超基性岩地球化学特征及对松多古特提斯洋演化的启示

唐加-松多古特提斯缝合带的提出改变了地学界对青藏高原古特提斯演化格局的认识。为进一步约束唐加-松多古特提斯缝合带中蛇绿岩的岩石成因及类型, 以松多地区的超基性岩为研究对象, 对其进行了岩石学和全岩地球化学研究。结果显示, 松多地区超基性岩与原始地幔相比具有较高的MgO和TFe2O3含量, 以及较低的Al2O3和TiO2含量。样品稀土元素总含量介于4.04×10-6~9.31×10-6之间, 大部分低于原始地幔值。稀土元素配分曲线呈较宽缓的"U"型, 轻稀土元素较富集。微量元素分布形式与全球深海橄榄岩的微量元素分布形式基本一致, 具有明显的Th、Nb负异常, 大部分样品具有轻微的Zr、Hf负异常。定量模拟估算表明, 研究区超基性岩主要为尖晶石二辉橄榄岩地幔批式熔融后的难熔残留体, 熔融程度大于25%, 并具一定程度石榴子石相熔融的特征, 未受到后期岩石-熔体反应的改造, 其原岩应为亏损的深海橄榄岩。结合区域研究成果, 松多地区超基性岩可能形成于大洋中脊(MOR)环境, 为典型的大洋中脊玄武岩(MORB)型蛇绿岩端元之一。     

Abyssal peridotites >3,800 Ma from southern West Greenland: field relationships, petrography, geochronology, whole-rock and mineral chemistry of dunite and harzburgite inclusions in the Itsaq Gneiss Complex

Within the northern part of the early Archaean Itsaq Gneiss Complex (southern West Greenland) on the southern side of the Isua supracrustal belt, enclaves up to ~500 m long of variably altered ultramafic rocks contain some relics of unaltered dunite-harzburgite. These are associated with mafic supracrustal and plutonic rocks and siliceous metasediments. SHRIMP U/Pb zircon geochronology on non-igneous zircons in altered ultramafic rocks and on igneous zircons from components of the surrounding orthogneisses intruding them, indicate an absolute minimum age for the ultramafic rocks of ca. 3,650 Ma, but with an age of ca. 3,800 Ma most likely. The diverse ultramafic and mafic rocks with rarer metasediment were all first tectonically intercalated and then became enclosed in much more voluminous tonalitic rocks dated at ca. 3,800 Ma. This is interpreted to have occurred during the development of a 3,810-3,790-Ma composite magmatic arc early in the evolution of the Itsaq Gneiss Complex. This northern part of the Itsaq Gneiss Complex is the most favourable for the geochemical study of early Archaean protoliths because it experienced peak metamorphism only within the amphibolite facies with little or no in-situ melt segregation, and contains some areas that have undergone little deformation since ca. 3,800 Ma. Most of the ultramafic enclaves are thoroughly altered, and largely comprise secondary, hydrous phases. However, the centres of some enclaves have escaped alteration and comprise dunite and harzburgite with >95% olivine (Fo_89-91) + orthopyroxene (En₈₉) + Al-spinel (Cr_8-20) assemblages. The dunites and harzburgites are massive or irregularly layered and are olivine-veined on 5-10-m to 10-cm scales. Their whole rock major and rare earth element, and olivine and spinel compositions differ significantly from xenoliths representing the Archaean cratonic lithospheric mantle, but are typical of some modern abyssal peridotites. The harzburgites and dunites show both LREE depleted and enriched patterns; however, none show the massive REE depletion associated with the modelled removal of a komatiite. They are interpreted as being the products of small degrees of melt extraction, with some showing evidence of refertilisation. These Greenland dunites and harzburgites described here are currently the best characterised 'sample' of the early Archaean upper mantle.     

Stratigraphic implications of heterogeneous deformation in the Jones Creek conglomerate (Archaean), Kathleen Valley,Western Australia

Rudaceous felsic to ultramafic clastic rocks of the Jones Creek Conglomerate are in tectonic contact with supracrustal mafic and ultramafic igneous rocks and associated fine‐grained sediments. All these rocks have a lower amphibolite facies mineralogy. Heterogeneously developed penetrative deformation has allowed sedimentary structures, including an unconformable contact between the Conglomerate and an adamellite, to be preserved in places. However, narrow, strike‐oriented zones containing blastomylonites and very flattened rudites normally characterize both contacts of the Conglomerate. Structural complexities within and at the contacts of the Conglomerate cast doubt on previous postulates that the Conglomerate separates an older from a younger supracrustal cycle.     

Serpentinites and related rocks of Anglesey

A series of ultramafic igneous bodies occurs in the Pre-Cambrian (Monian) metasedimentary rocks of Anglesey. The latter are finely-banded semi-pelites of greenschist facies and have undergone two main phases of deformation. Most of the structures are weakly developed near the intrusions where an irregular zone of epidote hornfels was produced. The ultramafic bodies were emplaced as peridotite magmas immediately prior to D. Thorough serpentinization followed and the resulting serpentinites have a variety of appearances. A later carbonatization was intense in places. The structures and textures of the intrusive rocks can be correlated with regional events. Various melagabbroic rocks, now highly altered, may be comagmatic with the peridotite although intruded rather later.     

Ultramafic rocks of the Widgiemooltha-Norseman area,Western Australia: Petrological diversity,geochemistry and mineralisation

Mineral exploration of the Widgiemooltha-Norseman region of Western Australia has located massive and disseminated nickel sulphide mineralisation.This paper discusses the geological setting of the nickel sulphide mineralisation with reference to the stratigraphy, structure and metamorphism of the ultramafic sequence and spatially associated rocks. The amphibolite facies metamorphosed ultramafic rocks of the Widgiemooltha area are compared with greenschist metamorphosed ultramafic rocks at Eundynie, which exhibit excellently preserved pseudomorphs of primary igneous textures.Some 2000 ultramafic rock samples were analysed for 13 element/oxides and divided into four major mineralogically and texturally distinct groups. The data were analysed statistically by determination of means and standard deviations and multiple regression analyses.The data suggest differentiation of a magma at depth followed by a vast outpouring of lava to produce picritic-peridotitic rocks. The flows crystallised with upper spinifex zones and lower euhedral-olivine zones in varying proportions dependent on magma composition. The development of spinifex texture is compositionally controlled. This texture is not developed in rocks with MgO contents greater than 26% (± 2%).The comparison of the ultramafics of the Widgiemooltha and Eundynie areas indicates that talc-carbonate formation and serpentinization have modified primary igneous textures and geochemistries, resulting in the production of a diverse group of rock types. Such post-magmatic alteration processes in association with structural elements are considered important in the upgrading of nickel sulphide mineralisation.     

Talc mineralization of ultramafic affinity in the Eastern Desert of Egypt

Petrographical and petrochemical studies of the talc host rocks of Rod Umm El-Farag and Wadi Thamil in the Eastern Desert of Egypt reveal that they consist mainly of metavolcanic rocks, whilst the geology, petrography, mineralogy, chemistry and quality of the enclosed talc lenses reveal that the ore has ultramafic affinity. The setting of the talc ore is similar to that hosted by metavolcanic rocks in terms of the type of host rocks, but it differs in its ultramafic affinity, resembling the talc ore hosted by ultramafic rocks. The parent ultramafic rocks occur in the form of small bodies obducted later along a tectonized fault plane within metavolcanic host rocks (Precambrian) and their tuffaceous equivalents. The metavolcanic host rocks consist mainly of metabasalts, meta-andesites and metatuffs with a smaller amount of dacite, rhyolite and tuffaceous lava. The metamorphic grade is low corresponding to greenschist facies. The calc-alkaline and tholeiitic characters of the volcanic rocks are determined by the behaviour of trace elements on some chemical discrimination diagrams. After the emplacement of the ultramafic bodies, they underwent regional metamorphism which was accompanied by further serpentinization. Metasomatic changes, related to regional metamorphism (corresponding to the emplacement of granitic plutons at a distance) include talc, carbonate, tremolite and chlorite formation. SiO₂, H₂O and CO₂ have been supplied from hydrothermal solutions but all other constituents are considered indigenous to the ultramafic bodies, and none of the metavolcanic components have been added during talc formation. Mineralogically, the talc ore is relatively simple, including talc, tremolite, actinolite, chlorite and chromite. On the basis of mineral abundances, pure talc (>90% talc), chlorite-rich and tremolite-actinolite-rich (50–70% talc) ore types have been recognized. Chromite is largely zoned and occurs as disseminated grains within the talc matrix. Cr, Al and Mg were released during the formation of ferrite chromite and accommodated in the talc and chlorite structures. The chemical data show that there is very little variation in the contents of MgO, Fe₂O₃, FeO, NiO, Cr₂O₃, and Co between the parent ultramafic rocks and talc ore. Al₂O₃, CaO, Fe₂O₃ and FeO are the main impurity oxides in the talc ore. They decrease the whiteness of the ore and consequently limit the use of talc. Received: 26 March 1999 / Accepted: 10 October 1999     

Petrochemistry and mineral chemistry studies on metamorphic ultramafic rocks in Yanghou area, Northern Fujian, China

Petrochemical studies indicate that the Yanghou metamorphie ultramafic rocks are composed of metamorphosed harzburgite and ultramafic cumulate.Trace element geochemistry and mineral chemistry of the metamorphic harzburgite indicate that they are relicts of depleted mantle.Systematic petrochemical,mineral chemical and geochronological studies led to such a conclusion that the Yanghou metamorphic ultramafic rocks may be the components of Late Sinian-Early Paleozoic ophiolite in South China.     

西藏阿里西部地区超镁铁岩的岩石化学及其上地幔化学模式的探讨

本文探讨了该区超镁铁岩化学成分的分带性;本区方辉橄榄岩与其它地区的化学成分的对比;以及与其密切共生的岩浆岩化学成分的互补关系;及本区上地幔可能的化学分带模式。得出结论:(1)从地质和岩石化学证据表明本区的方辉橄榄岩是地幔物质呈固态侵位的。(2)方辉橄榄岩与共生的岩浆岩有成因联系。(3)本区可能存在上地幔双层化学模式。     

The Khan-Taishir ophiolitic complex of Western Mongolia,its petrology,origin and comparison with other ophiolitic complexes

The Khan-Taishir ophiolitic complex is situated within Early Caledonian structures of Western Mongolia. It consists (from below upward) of strongly differentiated ultramafics (dunites and harzburgites), pyroxenites and gabbro, sheeted dikes, pillow lavas and sediments, including in their uppermost part archaeocyatic limestones of Lower Cambrian age. Geological, petrochemical and geochemical data indicate that the ultramafics are turn off from the overlying ophiolitic sequence. Igneous rocks of the ophiolitic complex, except the ultramafics, were formed by two-stage differentiation of mantle magma of quartz-tholeiitic composition exhausted in potassium and titanium. Pyroxenites and gabbro with an anorthositic trend of differentiation were generated during the first stage, and sheeted dikes and pillow lavas with a quartz trend of differentiation were formed during the second one. Ophiolites of the Khan-Taishir complex petrochemically and geochemically differ strongly from mafic and ultramafic rocks of midoceanic ridges. Together with ophiolites of the Troodos complex (Cyprus) and Macquarie Island (eastern Indian Ocean) they constitute the special type of ophiolite peculiar rather to slip boundaries of lithosphere plates. The other type of ophiolite, including complexes like the Dzolen complex of south Mongolia, contains poorly differentiated ultramafics and does not contain sheeted dikes; while the igneous rocks are very similar to mafic and ultramafic rocks dredged from midoceanic and formed probably in midoceanic ridge environments as well.     

Baddeleyite and zircon U-Pb ages of the ultramafic rocks in Chigu Tso area,Southeastern Tibet and their constraints on the timing of Comei Large Igneous Province

A suite of ultramafic and mafic rocks developed in the Chigu Tso area, eastern Tethyan Himalaya. Baddeleyite and zircon U-Pb ages acquired by SIMS and LA-ICP-MS from olivine pyroxenite rocks in the Chigu Tso area are 138.9±3.0 Ma and 139.0±1.9 Ma, respectively. These two Early Cretaceous ages are similar with the ages of the more abundant mafic rocks in the eastern Tethyan Himalaya, indicating that this suite of ultramafic and mafic rocks in the Chigu Tso area should be included in the outcrop area of the Comei Large Igneous Province (LIP). These ultramafic rocks provide significant evidence that the involvement of mantle plume/hot spot activities in the formation of the Comei LIP. Baddeleyite U-Pb dating by SIMS is one reliable and convenient method to constrain the formation time of ultramafic rocks. The dating results of baddeleyite and zircon from the olivine pyroxenite samples in this paper are consistent with each other within analytical uncertainties, suggesting that baddeleyite and zircon were both formed during the same magmatic process. The consistency of baddeleyite U-Pb ages in the Chigu Tso area with zircon U-Pb ages for a large number of Early Cretaceous mafic rocks in the eastern Tethyan Himalaya further support that zircon grains from such mafic rocks yielding Early Cretaceous ages are also magmatic in origin.     

苏北东海地区超高压变质带内的斜卧褶皱

详细的野外观察和制图证实，在苏北东海地区的驼峰、房山及虎山等超高压（UHP）变质带岩石出露地段，都有不同尺度的斜卧褶皱发育。在详细地描述了典型的斜卧褶皱组成、几何形态、位态及其形成的物理环境之后，指出斜卧褶皱及分隔它们的韧性剪切带，在构造上，是组成超高压变质带构造柱的两个基本要素，是在超高压变作用期后伸展体制及角闪岩相条件下形成的。同超高压变质作用的残余构造，只保留于大的榴辉岩和超镁铁质结构透镜体核部。无疑，在超高压变质岩石露头区地表构造研究所得的结果，对在东海地区第四纪沉积物所掩盖区实施的大陆科学钻探工程中揭露的地质现象解释，有重要参考意义。强调指出，大陆科学钻探工程所揭示的地壳构造，可能主要代表角闪岩相及伸展体制下的变形特征。     

Geochemical Features, Age, and Tectonic Significance of the Kekekete Mafic-ultramafic Rocks, East Kunlun Orogen, China

The Kekekete mafic-ultramafic rocks are exposed in the Kekesha-Kekekete-Dawate area,which are in the eastern part of the East Kunlun Orogenic Belt.It outcrops as tectonic slices intruding tectonically in the Paleoproterozoic Baishahe Group and the Paleozoic Nachitai Group.The Kekekete mafic and ultramafic rocks is located near the central fault in East Kunlun and lithologically mainly consists of serpentinite,augite peridotite,and gabbro.The LA-ICP-MS zircon U-Pb age of the gabbro is 501±7 Ma,indicating that Kekekete mafic-ultramafic rocks formed in the Middle Cambrian.This rock assemblage is relatively poor in SiO2 and(Na2 O+K2 O) but rich in MgO and SFeO.The chondrite-normalized REE patterns of the gabbro dip slightly to the right;the primitive mantle and MORBnormalized spidergrams of trace elements show enrichment of large-ion lithophile elements(Cs,Rb,Ba,etc.) and no differentiation of high field strength elements.The general dominance of E-MORB features and the geochemical characteristics of OIB suggest that the Kekekete mafic-ultramafic rocks formed in an initial oceanic basin with slightly enriched mantle being featured by varying degrees of mixing of N-MORB depleted mantle and a similar-OIB-type source.From a comprehensive study of the previous data,the author believes that the tectonic history of the East Kunlun region was controlled by a geodynamic system of rifting and extension in the late stages of the Neoproterozoic to early stages of the Early Paleozoic and this formed the paleo-oceanic basin or rift system now represented by the ophiolites along the central fault in East Kunlun,the Kekekete mafic-ultramafic rocks and Delisitan ophiolite.