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1.
贵州镇远马坪"东方一号"岩体为中国最早发现的原生金刚石矿,受当时只有金伯利岩才含金刚石矿及后来西澳阿盖尔钾镁煌斑岩型金刚石原生矿等的影响,先后定名为金伯利岩、钾镁煌斑岩、金云火山岩等。最近专题调查分析研究表明,镇远马坪地区含金刚石母岩,其岩石学矿物学和地球化学特征均更接近澳大利亚典型金伯利岩,白坟地区岩体则类似于澳大利亚典型钾镁煌斑岩,建议将镇远马坪地区"东方一号"等岩类定名为角砾凝灰质金伯利岩,白坟地区岩类定名为钾碱镁闪石-透辉石-金云母钾镁煌斑岩,镇远地区兼有金伯利岩和钾镁煌斑岩的特征,与西澳大利亚极其类似,镇远地区乃至黔东地区具有较大的金刚石原生矿找矿勘查潜力和研究意义。  相似文献   

2.
岩石圈热结构和热状态的研究对于大陆裂解、变质作用及活化构造形成机制等大陆动力学问题的研究十分重要。通过地球化学、构造地质学和综合分析,以贵州省镇远地区金伯利岩-钾镁煌斑岩和黔东—湘西一带的晚元古代地层为例,研究了扬子地块东南缘早古生代岩石圈热结构与热状态。提出高放射性元素产热率的HHPRM型地幔源区,进一步讨论HHPRM型地幔源区形成与演化的大陆动力学机制。认为古富集地幔(HHPRM型地幔源区)是镇远一带的早古生代钾镁煌斑岩-金伯利岩的岩浆源区,镇远地区金伯利岩-钾镁煌斑岩岩浆源区深度(H)在208~244km,形成温度在1547~1403℃间,该温度和深度范围属软流层,具有形成金刚石矿床的地质条件。建议在贵州—湖南—广西三省交界区的金伯利岩和钾镁煌斑岩岩群中应进一步开展金刚石矿床研究与勘查工作。  相似文献   

3.
前言     
近年来,我国的地质工作者对金伯利岩、钾镁煌斑岩及有关岩石的综合研究日趋深入,一个重要的特点是,这些研究密切地结合了金刚石的找矿工作。要想科学地确定找矿远景地区,必须掌握已发现的原生金刚石产地的基底构造、深部构造、岩石圈演化、岩体时代、寄主岩性质以及包括金刚石在内的找矿指示矿物的物理和化学特征,这样才能进一步有效地开展新一轮的找矿工作。本文集收集了近年来在上述研究领域内取得明显进展的某些代表性论文,主要内容涉及到有关我国原生金刚石产地的岩石圈性质、同位素特征、指示矿物找矿方法、金刚石多源性、金刚石包裹体、金伯利岩和钾镁煌斑岩的集群特征与找矿意义等方面;并报道了某些含矿性差的金伯利  相似文献   

4.
长期以来,人们把金伯利岩当作金刚石主要原岩.在七十年代中期在澳大利亚西部的金伯利地区相继发现了一种含金刚石的钾镁煌斑岩(金云火山岩),其中阿盖尔矿区AKI号岩筒有很大经济价值,估计储量约五亿克拉(约占世界总储量1/3).钾镁煌斑岩类的发现,扩大了寻找原生金刚石的领域.目前世界各国都在寻找钾镁煌斑岩,我国山东、四川也相继发现钾镁煌斑岩.  相似文献   

5.
本文综合了近年来国外几种含金刚石岩系及相关岩石的地球化学研究成果,总结了不同类型金伯利岩、金伯利岩与钾镁煌斑岩、含矿的与非含矿的含金刚石岩系的地球化学标志,并探讨了其源区的特征。  相似文献   

6.
金刚石通常出现于金伯利岩、钾镁煌斑岩及由这些岩石风化剥蚀产生的沉积物中。会刚石是在上地幔即位于岩石圈与软流圈交界处,距地表约150~200公里深处,压力45—60×10~7pa,温度约1140~1400℃高温高压条件下,由CO_2还原或CH_4氧化而成。根据南非金伯利岩岩管中金刚石内包体矿物同位素年龄测定,金刚石在33亿年前已形成,而金伯利岩形成于90百万年。西澳阿盖尔钾镁煌斑岩岩管形成时代为12.06亿年  相似文献   

7.
扬子地台周缘钾镁煌斑岩 Nd、Sr同位素特征介于南非Ⅰ、Ⅱ型金伯利岩和西澳与北美钾镁煌斑岩两种变化趋势之间,不同岩区间同位素组成差异反映地台周边构造性质不同,Pb同位素特征表明晚太古代地幔岩石圈具U亏损特征。  相似文献   

8.
应用统计法作金刚石找矿中铬铁矿的属性判别   总被引:1,自引:0,他引:1  
根据金伯利岩、钾镁煌斑岩、金刚石包体及其它岩石中铬铁矿电子探针分析成果的统计,发现铬铁矿随着Cr_2O_3含量的降低,其它组分具有四种演化趋势。一般一种岩石中的铬铁矿只有一种演化趋势,唯有金伯利岩、钾镁煌斑岩中有两种演化趋势共存。根据统计资料,采用Cr_2O_3-TiO_2、Cr_2O_3-Al_2O_3和MgO含量,建立了金伯利岩、钾镁煌斑岩中铬铁矿属性判别图,图中三个区间可提供岩石类型、含矿性及保存性三种信息。  相似文献   

9.
初论金刚石原生矿床成矿系列   总被引:1,自引:0,他引:1       下载免费PDF全文
银剑钊 《地球科学》2000,25(4):380-383
目前所知产金刚石的岩石类型包括金伯利岩、钾镁煌斑岩、榴辉岩、蛇绿岩套、碱性超基性杂岩、碱性超基性煌斑岩和橄榄岩类(方辉橄榄岩、纯橄榄岩等) 等偏碱性超镁铁质岩石, 而有经济价值的金刚石原生矿床仅见于金伯利岩和钾镁煌斑岩中, 除此之外的其他岩石类型中仅见有少量微粒金刚石.金伯利岩和钾镁煌斑岩都起源于地幔深部, 就此意义上讲, 二者是同源的, 但其岩石化学成分、主要矿物组成、产出大地构造背景以及同位素资料等, 却存在着比较明显的差异.由此构成了金刚石原生矿床的两个成矿系列: 金伯利岩成矿系列和钾镁煌斑岩成矿系列.金伯利岩成矿系列又可以根据其化学成分划分为3个亚系列, 即: 高Cr, Ti, Mg成矿亚系列, 低Cr, Ti, Mg成矿亚系列和介于二者之间的一种具有复杂化学成分的成矿亚系列.钾镁煌斑岩成矿系列则可以根据其主要矿物组成, 划分出橄榄石钾镁煌斑岩成矿亚系列、白榴石钾镁煌斑岩成矿亚系列以及介于两者之间的白榴石-橄榄石钾镁煌斑岩成矿亚系列共3种次级成矿系列.与此同时, 无论是金伯利岩成矿系列, 还是钾镁煌斑岩成矿系列, 又都可以根据其野外地质产状, 划分为以下3个成矿亚系列(形成时间从早到晚) : (1) 火山沉积凝灰岩成矿亚系列; (2) 火山凝灰角砾岩成矿亚系列; (3) 火山-次火山侵入相成矿亚系列.   相似文献   

10.
龙昭陵 《物探与化探》1999,23(3):185-190194
金刚石幔源成因论认为金刚石在岩石圈底部、软流圈顶部生成,金伯利岩或钾镁煌斑岩仅为载体将其带出成矿,重力均衡异常既反映地壳深处构造活动,又反映其活动的近期性,为此,要特别注意沅水流域年轻的含金刚石岩体的查找  相似文献   

11.
Based on original data on the East European and Siberian platforms and materials on the best studied foreign objects, a comparative analysis of kimberlites and lamproites was conducted and the criteria of their differences were formulated. Among most significant differences are the following: (1) the high-Mg potassic rocks (kimberlites and lamproites) show major-component variations, which are significantly wider in lamproites as compared to kimberlites. Kimberlites differ from lamproites not only in the content of SiO2, but also in alkalis, volatiles, and some trace elements. Kimberlites are characterized by CO2-dominated regime, whereas formation of lamproites was assisted by essentially H2O fluid; (2) Kimberlites are localized within ancient cratons, while within-plate lamproites are restricted to adjacent Proterozoic belts. Kimberlites are produced in the low-heat flow regions, whereas lamproites occur in the high-heat flow regions; (3) Kimberlites and lamproites were formed in different time; in particular, most productive kimberlitic magmatism was observed in the EEP and SP in the Devonian; (4) Kimberlite and lamproite bodies have different morphology: lamproites compose small subvolcanic bodies with lava flows, while kimberlites form volcanic pipes with no lavas; (5) Kimberlites contain highly silica-undersaturated minerals, while ultrabasic lamproites—silica-undersaturated ones; priderite and wadeite, the characteristic accessory minerals of lamproites, are not observed in kimberlites; (6) The primary melts of kimberlites and lamproites were derived from different types of mantle. The moderate and low-Ti kimberlites were generated from BSE or EMI type mantle. Precisely these types of kimberlites host diamond deposits, including economic grade objects in EEP. The lamproite sources were localized only in the enriched mantle (EMI and EMII). At the same time, these rocks share some similarities, primarily, with respect to their genesis and classification. Diamonds are common accessory minerals of kimberlites (low-Ti and some other types), but are observed only in only lamproite variety—olivine lamproites.  相似文献   

12.
A.L. Jaques  P.R. Milligan 《Lithos》2004,77(1-4):783-802
The distribution of kimberlite, lamproite and related alkaline volcanism in Australia can be broadly related to the structure of the Australian continent and lithosphere. Diamondiferous kimberlites and lamproites, with the apparent exception of the weakly diamondiferous Orrorro kimberlites in the Adelaide Fold Belt, lie within the large Precambrian shield where seismic tomographic models and heat flow data indicate the presence of relatively cold, high seismic wave speed lithosphere (tectosphere) typically some 200 km thick or more beneath the Archaean cratons and up to 300 km in parts of central Australia. Many of the diamondiferous intrusions appear to lie at the margins rather than in the centre of the lithosphere domains. The highest concentration of diamondiferous intrusions (kimberlites and lamproites) is on and around the Kimberley Craton where seismic data indicate crustal thicknesses of 35–40 km and a lithosphere up to 275 km thick that is distinct from Proterozoic northern Australia.

Many, but clearly not all, of the intrusions show evidence of regional and local structural controls. Some are spatially associated with known crustal structures, especially regional faults. Others are aligned, either singly or in clusters, along or near discontinuities and/or gradients evident in regional scale potential field data, especially the total horizontal gradients of gravity data continued upward tens to hundreds of kilometres. Many of these features are not evident in the original datasets as their signatures are masked by shorter wavelength (near surface) anomalies. In some cases, the kimberlites and associated rocks lie within crustal blocks and domains defined by discontinuities in the potential field data rather than at domain boundaries.

Our overview suggests that analysis of potential field data, especially horizontal gradients in upwardly continued potential field data, at all scales can assist definition of crustal and, potentially, lithospheric structures that may influence the distribution of diamond pipes. However, more definitive mapping of Australia's diamond prospective regions requires the integration of data on crustal structures, especially trans-lithospheric faults, and geodynamic settings with high resolution tomographic models and other geophysical, petrologic, and isotopic information on the nature of the lithosphere beneath the Australian continent.  相似文献   


13.
讨论了国内外用磁法普查金伯利岩的问题。与现代质子磁力仪的精度相适应,金伯利岩按磁性分为四类:实际无磁性的、弱磁性的、磁性的、强磁性的。大多数金伯利岩和钾镁煌斑岩是弱磁性的或磁性的。金伯利岩管的磁性无论在平面上和沿深度都是不均匀的。航空磁测普查金伯利岩和钾镁煌斑岩取得良好效果的3个条件中,最重要的是围岩磁性干扰水平低。  相似文献   

14.
产于克拉通地块及其边缘褶皱带金伯利岩和钾镁煌斑岩中的原生金刚石 ,其主体上属地幔捕虏晶并具复杂的生长历史。从克拉通岩石圈存在复杂多发的壳幔相互作用和多层次的流体活动事件的角度 ,结合金刚石的精细内部结构所反映的不连续生长及微区原位傅立叶变换红外光谱研究成果 ,认为具复杂生长环带的金刚石是克拉通地块内部增生过程中的地幔流体对已形成金刚石间的相互作用的产物。这一认识有助于增进金刚石微观结构与地块内部改造事件有机联系的研究。地幔交代作用的介质成分主要为SiO2 不饱和的碳酸岩熔体或富含不相容微量元素的CHON流体。多种年龄数据所给出的 1 1~ 1 2Ga结果 ,可能反映华北地块东部的岩石圈深部存在一次明显的地幔增生改造过程。  相似文献   

15.
郑建平  路凤香 《地学前缘》1996,3(4):187-194
古生代含捕虏体的金伯利岩和新生代含捕虏体的玄武岩同出于华北地台,提供了研究自古生代以来岩石圈演化的深源探针。古生代含金伯利岩的侵位表明古生代时曾存在冷厚的岩石圈;而新生代含捕虏体玄武岩的喷发,表明新生代时存在热薄的岩石圈。岩石圈减薄与“大洋化”是层圈物质交换作用在一定历史阶段中的反映。地幔流体是地幔演化产物,反之又作用于地幔演化。富含地幔流体的幔内剪切带及交代矿物层作为幔内软薄弱带,存在热、流体、化学及机械的耦合,是岩石圈减薄拆沉作用的重要界面位置。  相似文献   

16.
从31届地质大会看火成岩石学的研究动向   总被引:6,自引:0,他引:6       下载免费PDF全文
主要根据第31届国际地质大会上关于花岗质岩浆作用与成矿,花岗岩系统及元古宙岩石圈过程,玄武岩,碱性侵入体的成因与侵位,碳酸岩、金伯利岩、钾镁粕斑岩及相关岩石,造山带酸性与中性火山岩,火山作用等方面的发言、论文及摘要,结合其它资料,对近些年来国际、国内火成岩石学领域的新进展和研究动向进行讨论。认为从20世纪末到21世纪初,在地球动力学和全球变化的总框架下,在人类对资源、环境、减灾重大需求的推动下,火成岩石学在地球物质科学、岩石探针、大火成岩省事件与超级地幔柱、地幔动力学、岩浆过程的物理学及超高压实验等方向取得了明显的进展。  相似文献   

17.
Kimberlites, carbonatites and ultramafic, mafic and potassic lamprophyres have been produced in West Greenland in recurrent events since the Archaean. Five distinct age groups are recognised: Archaean (>2500 Ma). Early Proterozoic (1700–1900 Ma), Middle Proterozoic (Gardar, c. 1100–1300 Ma), Late Proterozoic (600 Ma) and Mesozoic-Tertiary (200-30 Ma) The rocks comprise two large and four small carbonatite occurrences, four kimberlite dyke swarms, one lamproite dyke swarm and one lamproite pipe, one dyke swarm of potassic lamprophyre (shonkinite) and some ten dyke swarms of ultramafic lamprophyre and monchiquite. Geochemical data for the various rock groups are presented. Some of the carbonatites may represent relatively unmodified mantle-derived melts. The kimberlites range from primitive to differentiated compositions, and there are regional differences between kimberlites within Archaean and Proterozoic basement. The ultrapotassic lamproites and shonkinites have strong negative Nb spikes in their trace element spectra. The ultramafic and monchiquitic lamprophyres encompass a large compositional variation; however, several of the dyke swarms have individual chemical characters.

The rocks are very unevenly distributed in West Greenland, indicating a lithospheric control, probably by old weakness zones providing access to the surface. The kimberlites are considered to be mainly of asthenospheric derivation. The regional differences are interpreted in terms of melting with phlogopite as a residual phase, with smaller degrees of melting at deeper levels beneath the Archaean lithosphere than beneath the Proterozoic. The ultrapotassic lamproites and shonkinites occur almost exclusively within a continental collision zone with possible two-way subduction and they are interpreted as mainly of lithospheric derivation, with a contribution from a subducted slab. Data for the other rock types are equivocal.

Except for the Archaean rocks, the age groups can be related to major geotectonic events. The Early Proterozoic group is related to continental collision at 1850 Ma and subsequent rifting; the Middle Proterozoic group is related to continental rifting (Gardar) and the Mesozoic group is likewise related to continental rifting prior to continental break-up in the Tertiary. The 600 Ma kimberlites and carbonatite are envisaged as cratonic, extra-rift activity in relation to continental break-up and formation of the Iapetus ocean further south, perhaps with a common cause in a broad, impinging mantle plume.  相似文献   


18.
华北地台东部有6个金伯利岩岩区,它们分布于古陆核的中心(如富矿的复县一蒙阴)、北缘(如贫矿的铁岭)及西缘元古代裂陷带(如无矿的涉县一鹤壁)。本文在不相容元素、同位素源区约束讨论的基础上,选择代表性的金伯利岩进行源区地球化学定量反演,进而讨论了源区的不均一性。金伯利岩产出的构造部位及由此所反映的岩石圈厚度、地慢流体活动强度的差异,不仅影响金伯利岩含金刚石性,而且也是地幔源区不均一性的影响因素  相似文献   

19.
Chemical, mineralogical and isotopic studies have been made on nodules of the MARID (Mica-Amphibole-Rutile-Ilmenite-Diopside) xenolith suite in southern African kimberlites. All are ultramafic and ultrapotassic (MgO= 20–25%, K2O=4–9%), with bulk compositions reflecting the wide variation in relative proportions of the five minerals amongst the nodules. They are comparable in major element compositions to magnesian lamproites, in particular the ultrabasic olivine-lamproites of Western Australia. In a number of high pressure experimental studies on ultra-potassic rocks, the phases produced between 25–30 kbar from compositions comparable to those of MARID rocks (in the presence of additional water), were predominantly phlogopite and diopside (±K-richterite, ±ilmenite, ±rutile). Furthermore the compositions of experimental minerals produced in the synthetic-biotite-mafurite-H2O system by Edgar et al. (1976) are similar to those in MARID rocks.It is suggested on the basis of these observations and the textural appearance of MARID rocks that they are magmatic compositional equivalents of MgO-rich lamproites that crystallized at high pressures. While lamproites have higher average concentrations of incompatible elements, (including REE), some MARID rocks have comparable abundances. It is suggested that late stage vapour-rich melts carrying substantial REE and other incompatible elements escaped from crystallizing MARID magmas into surrounding subcontinental lithosphere, thus resulting in lower levels of these elements in most MARID rocks. In contrast faster crystallization of lamproitic rocks under volcanic/ hypabyssal conditions would prevent similar losses.The MARID proto-magmas are thought to be either partial melts of metasomatised phlogopite peridotite, or small volume asthenospheric melts which are modified and further enriched by incorporation of small partial melts of enriched subcontinental lithosphere during magma ascent.  相似文献   

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