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1.
Major element and Re–Os isotope analysis of single sulfide inclusions in diamonds from the 240 Ma Jwaneng kimberlite has revealed the presence of at least two generations of eclogitic diamonds at this locality, one Proterozoic (ca. 1.5 Ga) and the other late Archean (ca. 2.9 Ga). The former generation is considered to be the same as that of eclogitic garnet and clinopyroxene inclusion bearing diamonds from Jwaneng with a Sm–Nd isochron age of 1.54 Ga. The latter is coeval with the 2.89 Ga subduction-related generation of eclogitic sulfide inclusion bearing diamonds from Kimberley formed during amalgamation of the western and eastern Kaapvaal craton near the Colesberg magnetic lineament.
The Kimberley, Jwaneng, and Premier kimberlites are key localities for characterizing the relationship between episodic diamond genesis and Kaapvaal craton evolution. Kimberley has 3.2 Ga harzburgitic diamonds associated with creation of the western Kaapvaal cratonic nucleus, and 2.9 Ga eclogitic diamonds resulting from its accretion to the eastern Kaapvaal. Jwaneng has two main eclogitic diamond generations (2.9 and 1.5 Ga) reflecting both stabilization and subsequent modification of the craton. Premier has 1.9 Ga lherzolitic diamonds that postdate Bushveld–Molopo magmatism (but whose precursors have Archean Sm–Nd model ages), as well as 1.2 Ga eclogitic diamonds. Thus, Jwaneng provides the overlap between the dominantly Archean vs. Proterozoic diamond formation evident in the Kimberley and Premier diamond suites, respectively. In addition, the 1.5 Ga Jwaneng eclogitic diamond generation is represented by both sulfide and silicate inclusions, allowing for characterization of secular trends in diamond type and composition. Results for Jwaneng and Kimberley eclogitic sulfides indicate that Ni- and Os-rich end members are more common in Archean diamonds compared to Proterozoic diamonds. Similarly, published data for Kimberley and Premier peridotitic silicates show that Ca-rich (lherzolitic) end members are more likely to be found in Proterozoic diamonds than Archean diamonds. Thus, the available diamond distribution, composition, and age data support a multistage process to create, stabilize, and modify Archean craton keels on a billion-year time scale and global basis. 相似文献
2.
Steven B. Shirey Jeffrey W. Harris Stephen H. Richardson Matthew Fouch David E. James Pierre Cartigny Peter Deines Fanus Viljoen 《Lithos》2003,71(2-4):243-258
The Archean lithospheric mantle beneath the Kaapvaal–Zimbabwe craton of Southern Africa shows ±1% variations in seismic P-wave velocity at depths within the diamond stability field (150–250 km) that correlate regionally with differences in the composition of diamonds and their syngenetic inclusions. Seismically slower mantle trends from the mantle below Swaziland to that below southeastern Botswana, roughly following the surface outcrop pattern of the Bushveld-Molopo Farms Complex. Seismically slower mantle also is evident under the southwestern side of the Zimbabwe craton below crust metamorphosed around 2 Ga. Individual eclogitic sulfide inclusions in diamonds from the Kimberley area kimberlites, Koffiefontein, Orapa, and Jwaneng have Re–Os isotopic ages that range from circa 2.9 Ga to the Proterozoic and show little correspondence with these lithospheric variations. However, silicate inclusions in diamonds and their host diamond compositions for the above kimberlites, Finsch, Jagersfontein, Roberts Victor, Premier, Venetia, and Letlhakane do show some regional relationship to the seismic velocity of the lithosphere. Mantle lithosphere with slower P-wave velocity correlates with a greater proportion of eclogitic versus peridotitic silicate inclusions in diamond, a greater incidence of younger Sm–Nd ages of silicate inclusions, a greater proportion of diamonds with lighter C isotopic composition, and a lower percentage of low-N diamonds whereas the converse is true for diamonds from higher velocity mantle. The oldest formation ages of diamonds indicate that the mantle keels which became continental nuclei were created by middle Archean (3.2–3.3 Ga) mantle depletion events with high degrees of melting and early harzburgite formation. The predominance of sulfide inclusions that are eclogitic in the 2.9 Ga age population links late Archean (2.9 Ga) subduction-accretion events involving an oceanic lithosphere component to craton stabilization. These events resulted in a widely distributed younger Archean generation of eclogitic diamonds in the lithospheric mantle. Subsequent Proterozoic tectonic and magmatic events altered the composition of the continental lithosphere and added new lherzolitic and eclogitic diamonds to the already extensive Archean diamond suite. 相似文献
3.
A.L. Ragozin D.A. Zedgenizov V.S. Shatsky K.E. Kuper 《Russian Geology and Geophysics》2018,59(5):486-498
Mosaic diamonds from the Zarnitsa kimberlite (Daldyn field, Yakutian diamondiferous province) are morphologicaly and structurally similar to dark gray mosaic diamonds of varieties V and VII found frequently in placers of the northeastern Siberian craton. However, although being similar in microstructure, the two groups of diamonds differ in formation mechanism: splitting of crystals in the case of placer diamonds (V and VII) and growth by geometric selection in the Zarnitsa kimberlite diamonds. Selective growth on originally polycrystalline substrates in the latter has produced radial micro structures with grains coarsening rimward from distinctly polycrystalline cores. Besides the formation mechanisms, diamonds of the two groups differ in origin of mineral inclusions, distribution of defects and nitrogen impurity, and carbon isotope composition. Unlike the placer diamonds of varieties V and VII, the analyzed crystals from the Zarnitsa kimberlite enclose peridotitic minerals (olivines and subcalcic Cr-bearing pyropes) and have total nitrogen contents common to natural kimberlitic diamonds (0 to 1761 ppm) and typical mantle carbon isotope compositions (-1.9 to -6.2%c 513C; -4.2%c on average). The distribution of defect centers in the Zarnitsa diamond samples fits the annealing model implying that nitrogen aggregation decreases from core to rim. 相似文献
4.
Integrated models of diamond formation and craton evolution 总被引：4，自引：0，他引：4
Two decades of diamond research in southern Africa allow the age, average N content and carbon composition of diamonds, and the dominant paragenesis of their syngenetic silicate and sulfide inclusions to be integrated on a cratonwide scale with a model of craton formation. Individual eclogitic sulfide inclusions in diamonds from the Kimberley area kimberlites, Koffiefontein, Orapa and Jwaneng have Re–Os isotopic ages that range from circa 2.9 Ga to the mid-Proterozoic and display little correspondence with the prominent variations in the P-wave velocity (±1%) that the mantle lithosphere shows at depths within the diamond stability field (150–225 km). Silicate inclusions in diamonds and their host diamond compositions for the above kimberlites, Finsch, Jagersfontein, Roberts Victor, Premier, Venetia, and Letlhakane show a regional relationship to the seismic velocity of the lithosphere. Mantle lithosphere with slower P-wave velocity relative to the craton average correlates with a greater proportion of eclogitic vs. peridotitic silicate inclusions in diamond, a greater incidence of younger Sm–Nd ages of silicate inclusions, a greater proportion of diamonds with lighter C isotopic composition, and a lower percentage of low-N diamonds. The oldest formation ages of diamonds support a model whereby mantle that became part of the continental keel of cratonic nuclei first was created by middle Archean (3.2–3.3 Ga or older) mantle depletion events with high degrees of melting and early harzburgite formation. The predominance of eclogitic sulfide inclusions in the 2.9 Ga age population links late Archean (2.9 Ga) subduction–accretion events to craton stabilization. These events resulted in a widely distributed, late Archean generation of eclogitic diamonds in an amalgamated craton. Subsequent Proterozoic tectonic and magmatic events altered the composition of the continental lithosphere and added new lherzolitic and eclogitic diamonds to the already extensive Archean diamond suite. Similar age/paragenesis systematics are seen for the more limited data sets from the Slave and Siberian cratons. 相似文献
5.
G. K. Khachatryan M. B. Kopchikov V. K. Garanin M. V. Chukichev N. N. Golovin 《Moscow University Geology Bulletin》2009,64(2):102-110
The morphological and spectral-optical properties of diamond crystals from placers in North Timan rivers have been studied with IR-spectroscopy and cathode luminescence methods. As a result, correlation between external characteristics of diamonds (size and degree of mechanical damage) and number of optically active centers has been revealed. The habit and the type of distribution of structural defects in diamond crystals studied are comparable with those in diamonds from the Archangelsk Region and North Timan’s placers. Based on the obtained data, origin issues and possible primary sources of diamonds from North Timan’s placers are discussed. 相似文献
6.
Large deposits of diamonds are associated mainly with kimberlites (and related rocks) of the cratons, but they are also known in the folded belts surrounding them. As an example is the Baltica craton and the surrounding its the Ural‐Timan (UT) folded belt. With the first object are associated diamonds of the Arkhangelsk (kimberlites and placers) provinces, and with the second one ‐ mostly placer deposits of the UT province, the probable source of which are also kimberlites. The structural position, composition and age of the potentially diamond‐bearing complexes of the Urals and Timan make it possible to propose a new petrological‐geodynamic interpretation of their formation. According to this model, during the Vendian‐Cambrian subduction of the Pechora Ocean crust, several different depth complexes have been formed, being changed in the western direction. At a shallow depth level the oceanic crust subduction is accompanied only by fluid processing, without the magmatism participation. As a result, this process leads to the formation of fluidizate‐explosive rocks of the Sertynya complex, which marks the outlet of the ancient subduction zone into the surface. At a moderately deep (up to 100–150 km) level melts are being produced, the derivatives of which are not diamond‐bearing depleted kimberlites of the Khartes (V‐Cm) complex. Apparently by the beginning of the Ordovician the active subduction of the Pechora Ocean stops. It occurs an opening of a new Ural paleoocean, and the earlier submerged the oceanic slab continues moving under the Baltica craton. At a deep (above 150 km) level the slab interaction with the mantle produces typical kimberlite magmas (from the Ordovician to the Middle Devonian) transporting diamonds to the surface of the Ural‐Timan province proper. 相似文献
7.
B. M. Mikhailov 《Lithology and Mineral Resources》2004,39(2):114-134
The presented overview of hypergene metallogeny of the Urals is largely based on original data of the author. All bauxite, Co–Ni oxide–silicate, and high-grade ferromanganese our deposits, gold, platinum, and diamond placers, as well as brown coal, kaoline, refractory, and other economic-grade mineral deposits, currently mined in the Urals are hosted in hypergene zones and related hypergene blankets of different ages. Prospects for diverse mineral deposits are estimated with a special emphasis on thermal hypergene deposits (Ni, Au, and others) that are atypical for the Urals but favorable for mining under conditions of the market economy owing to the presence of high-grade ore bodies. 相似文献
8.
N.S. Tychkov D.S. Yudin E.I. Nikolenko E.V. Malygina N.V. Sobolev 《Russian Geology and Geophysics》2018,59(10):1254-1270
Several thousand clinopyroxene, garnet, and phlogopite inclusions of mantle rocks from Jurassic and Triassic kimberlites in the northeastern Siberian craton have been analyzed and compared with their counterparts from Paleozoic kimberlites, including those rich in diamond. The new and published mineral chemistry data make a basis for an updated classification of kimberlite-hosted clinopyroxenes according to peridotitic and mafic (eclogite and pyroxenite) parageneses. The obtained results place constraints on the stability field of high-Na lherzolitic clinopyroxenes, which affect the coexisting garnet and decrease its Ca contents. As follows from analyses of the mantle minerals from Mesozoic kimberlites, the cratonic lithosphere contained more pyroxenite and eclogite in the Mesozoic than in the Paleozoic. It virtually lacked ultradepleted harzburgite-dunite lithologies and contained scarce eclogitic diamonds. On the other hand, both inclusions in diamond and individual eclogitic minerals from Mesozoic kimberlites differ from eclogitic inclusions in diamond from Triassic sediments in the northeastern Siberian craton. Xenocrystic phlogopites from the D’yanga pipe have 40Ar/39Ar ages of 384.6, 432.4, and 563.4 Ma, which record several stages of metasomatic impact on the lithosphere. These phlogopites are younger than most of Paleozoic phlogopites from the central part of the craton (Udachnaya kimberlite). Therefore, hydrous mantle metasomatism acted much later on the craton periphery than in the center. Monomineral clinopyroxene thermobarometry shows that Jurassic kimberlites from the northeastern craton part trapped lithospheric material from different maximum depths (170 km in the D’yanga pipe and mostly < 130 km in other pipes). The inferred thermal thickness of cratonic lithosphere decreased progressively from ~ 260 km in the Devonian-Carboniferous to ~ 225 km in the Triassic and to ~ 200 km in the Jurassic, while the heat flux (Hasterok-Chapman model) was 34.9, 36.7, and 39.0 mW/m2, respectively. Dissimilar PT patterns of samples from closely spaced coeval kimberlites suggest different emplacement scenarios, which influenced both the PT variations across the lithosphere and the diamond potential of kimberlites. 相似文献
9.
《International Geology Review》2012,54(9):42-46
The discovery of ultrabasic rocks and of diamonds in Upper Triassic-Lower Jurassic kimberlite pipes in the Siberian platform gave impetus to the search for diamond deposits in this area. Also, the discovery of diamond placers in Mesozoic and Cenozoic marine and nonmarine sediments in 1948 intensified the search. The geology of the area is characterized, as is that of the African diamond fields, by considerable faulting and heterogeneous composition of the basement, the development of large depressions, and a magmatic cycle dominated by basic and ultrabasic magmas. Many unexplored areas within the platform, undoubtedly having similar characteristics, are potential diamond producers. --G. E. Denegar. 相似文献
10.
Geology of Ore Deposits - Systematized information on the formation of all types of diamond placers in the Vishera diamondiferous zone is given for the first time. The method of retrospective... 相似文献
11.
本文收集大量锆石U-Pb年代学数据,通过制作年龄-频数图谱,简略探讨了西伯利亚克拉通、华北克拉通、东北地区微地块以及内蒙古大石寨地区的演化史,并对大石寨二叠系与其周边块体的锆石年龄作比较分析,进而探讨了大石寨地区二叠系的物源问题。碎屑锆石年龄-频数图表明,大石寨地区二叠系碎屑锆石年龄可以划分出古生代年龄段(500~250 Ma),中—新元古代年龄段(1.6~0.8 Ga),新太古一古元古代年龄段(2.6~1.7 Ga)。华北克拉通北缘与西伯利亚克拉通南缘基底年龄均1.6 Ga,其二者都不能反映大石寨地区二叠系物源年龄信息,而大石寨地区二叠系碎屑锆石年龄峰值与东北地区地块年龄峰具有很好一致性,说明二者锆石年龄峰值反映的构造岩浆事件一致,表明大石寨地区二叠系物源应来源于东北地块而不是华北克拉通和西伯利亚克拉通。同时,东北地区大量古老基底锆石年龄数据的存在,暗示东北地块可能独立于上述两大板块而存在,并响应中亚造山带内存在古老微大陆的观点;东北地块由诸多微小块体拼贴而成,并分别与西伯利亚克拉通和华北克拉通碰撞拼接,缝合线分别是贺根山一黑河缝合带与西拉木伦缝合带。 相似文献
12.
《International Geology Review》2012,54(5):826-831
Zircon-ilmenite placers in thin sandy clays of the West Siberian lowlands have been assigned ages ranging from Upper Cretaceous to Middle Oligocene. The productive beds were formed under continental conditions close to a Paleozoic sandstone source ridge. Inherited mineral composition, grain size and identical ore minerals are lines of evidence used to relate the placers to their source beds.—W. E. Yasso 相似文献
13.
S.A. Grakhanov Yu.A. Malanin V.I. Pavlov V.P. Afanas’ev N.P. Pokhilenko A.V. Gerasimchuk A.N. Lipashova 《Russian Geology and Geophysics》2010,51(1):127-135
Large diamond placers have been discovered in a Rhaetian basal horizon (Upper Triassic) in the north of the Sakha Republic (Yakutia) in the drainage areas of the Eekit, Nikabyt, Kelimyar, and Bur Rivers. In typomorphic features the found diamonds and indicator minerals of kimberlites are completely similar to those from Carnian basal horizons but, in contrast to them, are well sorted, and pyropes show features of mechanical wear. Analysis of the geologic evolution of the study area, morphology of diamonds and indicator minerals, and composition of the latter showed that the Rhaetian productive sediments resulted from the erosion of Carnian placers. 相似文献
14.
207Pb–206Pb ages of zircons in samples of metasediments as well as ortho- and para-gneisses from both the western and the eastern parts
of the Dharwar craton have been determined using an ion microprobe. Detrital zircons in metasedimentary rocks from both yielded
ages ranging from 3.2 to 3.5 Ga. Zircons from orthogneisses from the two parts also yielded similar ages. Imprints of younger
events have been discerned in the ages of overgrowths on older zircon cores in samples collected throughout the craton. Our
data show that the evolution of the southwestern part of eastern Dharwar craton involved a significant amount of older crust
(>3.0 Ga). This would suggest that crust formation in both the western and eastern parts of the Dharwar craton took place
over similar time interval starting in the Mesoarchaean at ca. 3.5 Ga and continuing until 2.5 Ga. Our data coupled with geological
features and geodynamic setting of the Dharwar craton tend to suggest that the eastern Dharwar craton and the western Dharwar
craton formed part of a single terrane. 相似文献
15.
In the Kaapvaal craton of southern Africa, as well as other Archaean cratons worldwide, the progression from dominant tonalite-trondhjemite-granodiorite(TTG) to granite-monzogranite-syenogranite(GMS)rock types is interpreted to reflect progressive reworking and differentiation of the continental crust.Here we re-evaluate the early Archaean evolution of the Kaapvaal craton and propose a unified view of the plutonic and volcanic records based on elemental and isotopic(Nd, Hf) data and zircon U-Pb ages.We also report new whole-rock major and trace element analyses, zircon U-Pb ages and Hf-in-zircon analyses of igneous clasts from a conglomerate of the 3.2 Ga Moodies Group of the Barberton Greenstone Belt. Many of these clasts are derived from shallow intrusive rocks of granitic composition, which are scarcely represented in outcrop. Despite alteration, the volcanic rocks can be classified based on their trace element contents into two main groups by comparison with plutonic rocks. One group has characteristics resembling TTGs: relatively low and fractionated rare earth element concentrations with no Eu anomaly and relatively low concentrations of high field strength elements(Nb mostly ≤12 ppm). The second group has GMS-like characteristics: less fractionated REE, marked negative Eu anomalies and HFSE-increasing trends with progressing fractionation(Nb ≤ 50 ppm or more, Th up to 30-40 ppm). In addition, igneous clasts of Moodies Group conglomerate have chemical, mineralogical and isotopic characteristics that link them to GMS. New analyses of some of these clasts indicate elevated high field strength elements(Nb up to 20 ppm) and_(εHf)(t)of zircon down to -3.5. These rocks imply the presence of an already differentiated felsic crust at 3.5 Ga, which has Nd and Hf model ages indicating mantle extraction ages extending back to the Eoarchaean. The combined record of plutonic and volcanic rocks of the Kaapvaal craton provides a more complex scenario than previously suggested and indicates that TTG and GMS-like felsic magmas were emplaced broadly coevally in multiple pulses between ~3.5 Ga and 3.2 Ga. 相似文献
16.
N. B. Kuznetsov T. V. Romanyuk A. V. Shatsillo S. Yu. Orlov V. M. Gorozhanin E. N. Gorozhanina E. S. Seregina N. S. Ivanova J. Meert 《Doklady Earth Sciences》2014,455(2):370-375
Several alternative points of view currently exist on the origin of the primary sources of diamonds from the Cenozoic Western Urals placers. Some researchers suppose that their economic diamond resource potential is related to diamonds from tuffisitic facies of the mantle kimberlites-lamproites or impact structures. Other researchers suggest that diamonds originated from the eroded sandstones of the Upper Emsian Takaty Formation of the Lower Devonian, which represents ancient (fossil) placers or intermediate reservoirs. It is assumed that these reservoirs collected diamonds from worn kimberlite bodies, which were located in the Urals or on the East European platform (EEP). This paper presents the first U-Pb (LA-ICP-MS) age of detrital zircons from quartz sandstones of the Takaty Formation, which spans a range from 1857.5 ± 53.8 to 3054.0 ± 48.0 Ma. The absence of detrital zircons younger than 1.86 Ga excludes that the structural complexes of the Uralian, Fennoscandian, and Sarmatian EEP parts were the provenance areas that supplied the clastic material to the sedimentary basin, which accumulated the Takaty Formation. The similar age of our zircons and ancient crystalline complexes of the Volga-Uralian EEP part allows consideration that it was a single provenance area. If we assume that the diamond resource potential of the Western Urals is completely or partly related to the ancient diamond placers from the Takaty Formation, then the intermediate diamond reservoirs from its structure originated due to redeposition of destruction products of primary diamond-bearing rocks of the Volga-Uralia area. Thus, within the Volga-Uralian part of the EEP basement, we may expect identification of a previously unknown stage of kimberlite formation, which is significantly older than that responsible for the diamond resource potential of the Arkhangel’sk province. 相似文献
17.
中国西秦岭碎屑锆石U-Pb年龄及其构造意义 总被引：5，自引：1，他引：4
西秦岭是北接华北克拉通、西接祁连与柴达木、南接松潘—甘孜地块的东秦岭造山带的西延。文中研究了该区从前寒武纪到三叠纪的碎屑沉积岩。这些碎屑沉积岩中分离出的锆石由LA-ICPMS(激光剥蚀等离子体质谱)进行了U-Pb定年。全岩Nd亏损地幔模式年龄类似于扬子克拉通年龄,主要分布于1.55~1.98Ga,峰值为1.81Ga,而与华北克拉通主要为古元古代与太古宙的模式年龄形成明显的对比。泥盆系中的碎屑锆石930~730Ma的U-Pb年龄指示其与扬子克拉通具亲缘性。930~730Ma是源区地壳的强烈增长阶段。二叠系—三叠系的碎屑沉积岩主体以含老于1600Ma的碎屑锆石为特征。碎屑锆石U-Pb年龄与Sm-Nd同位素组成指示此时华北克拉通南缘的基底岩石成为二叠系—三叠系碎屑沉积岩的重要物源。扬子克拉通在三叠纪时与华北克拉通拼接。西秦岭二叠系—三叠系碎屑沉积岩含有高达50%的华北克拉通南缘的基底岩石。 相似文献
18.
Afanasiev V. P. Pokhilenko N. P. Egorova E. O. Lindenblot E. S. 《Doklady Earth Sciences》2019,489(2):1409-1412
Doklady Earth Sciences - Based on a study of diamond grains from placers of the northeastern Siberian Platform, it is shown that certain types of diamonds (rounded dodecahedroids, diamonds of the... 相似文献
19.
《International Geology Review》2012,54(2):215-220
In the northeast Yakutian placers, 20 to 46% of the diamond crystals examined were found to be whole and undamaged (the Syungude and Daldyn placers respectively; the other vary within this range). By districts, percentages of whole crystals are higher in the Middle Olenek and the Anabar than in the Lena or the Beyenchime-Udzha. Regionally, 70 to 88% of the crystals are rhombododecahedral and the remainder - octahedral or of the intermediate habits. The colors are generally brown or yellow; lilac or colorless crystals are not abundant. The photoluminescence is generally none, blue or vague, but may be yellow green or orange red (5 to 11% of the crystals; 23% in the Anabar district). – IGR Staff. 相似文献
20.
Detrital Zircon Ages of Hanjiang River： Constraints on Evolution of Northern Yangtze Craton, South China 总被引：1，自引：0，他引：1
Clastic sedimentary rocks are natural samples of the exposed continental crust over large areas. The Hanjiang (汉江) River drains the northern Yangtze craton,including the South Qinling (秦岭) belt and the northern parts of the Yangtze craton. Detrital zircons from this river thus provide an ideal sample for studying the formation and evolution of the northern Yangtze craton. Here we report laser ablation inductively coupled plasma mass spectrometer U-Pb ages of 122 detrital zircons from one sand sample of the Hanjiang River. The 110 concordant zircons reveal four major age groups of 768,444,212,and 124 Ma,which well correlate with known magmatic events in the northern Yangtze craton. A minor group is present at 1 536 Ma,which is less known in the study area. Only seven zircons have ages of >1 750 Ma. Our results show that the Early Paleozoic,Late Triassic,and Early Cretaceous are important episodes of zircon growth and crustal growth/reworking in addition to the previously documented Neoproterozoic event. Our results suggest very limited exposures of Paleoproterozoic and Archean rocks in the northern parts of the Yangtze craton. 相似文献