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1.
山西大同钾镁煌斑岩地质地球化学特征 总被引：3，自引：0，他引：3
根据饮牛沟钾镁煌斑岩的岩石学、岩石化学、矿物化学、微量及稀土元素地球化学特征,本文认为该岩体属钾镁煌斑岩,但在矿物成分及化学成分上与世界上典型的含金刚石的钾镁煌斑岩相比,相对贫钛和钾,未出现含Ｋ,Ｂａ,Ｔｉ,Ｚｒ的副矿物。该岩体的成因可能为母岩部分熔融后又经分离结晶作用而形成的,岩浆起源于贫钛的金云母二辉橄榄岩,形成深度１００ｋｍ左右。 相似文献
2.
山东金刚石原生矿找矿前景探讨 总被引：4，自引：0，他引：4
金刚石形成于地幔深处,含金刚石的岩石只是一种运载和保存"工具",凡是来自上地幔的岩石均有可能携带早已形成的金刚石而形成金刚石原生矿床.世界上已知金刚石原生矿除金伯利岩、钾镁煌斑岩型外,尚在橄榄岩、橄榄玄武岩、千枚岩、科马提岩、榴辉岩等岩石中发现了金刚石,可能存在金刚石原生矿新的岩石类型.山东位于华北地台的南东部,鲁西、鲁东基底属A型克拉通,幔源岩浆活动强烈,具备良好的金刚石原生矿成矿地质条件,已获得的大量的成矿信息和找矿线索表明,除已发现的蒙阴金伯利岩型金刚石原生矿外,应该存在着尚未发现的金刚石原生矿,找矿前景广阔,应进一步加强金刚石原生矿勘查工作. 相似文献
3.
N. V. Chalapathi Rao 《Journal of Earth System Science》2006,115(1):161-183
Amongst all the perceptible igneous manifestations (volcanic tuffs and agglomerates, minor rhyolitic flows and andesites,
dolerite dykes and sills near the basin margins, etc.) in the Vindhyan basin, the two Mesoproterozoic diamondiferous ultramafic
pipes intruding the Kaimur Group of sediments at Majhgawan and Hinota in the Panna area are not only the most conspicuous
but also well-known and have relatively deeper mantle origin. Hence, these pipes constitute the only yet available ‘direct’
mantle samples from this region and their petrology, geochemistry and isotope systematics are of profound significance in
understanding the nature of the sub-continental lithospheric mantle beneath the Vindhyan basin. Their emplacement age (∼ 1100
Ma) also constitutes the only reliable minimum age constrain on the Lower Vindhyan Group of rocks. The Majhgawan and Hinota
pipes share the petrological, geochemical and isotope characteristics of kimberlite, orangeite (Group II kimberlite) and lamproite
and hence are recognised as belonging to a ‘transitional kimberlite-orangeite-lamproite’ rock type. The namemajhagwanite has been proposed by this author to distinguish them from other primary diamond source rocks. The parent magma of the Majhgawan
and Hinota pipes is envisaged to have been derived by very small (<1%) degrees of partial melting of a phlogopite-garnet lherzolite
source (rich in titanium and barium) that has been previously subjected to an episode of initial depletion (extensive melting
during continent formation) and subsequent metasomatism (enrichment). There is absence of any subduction-related characteristics,
such as large negative anomalies at Ta and Nb, and therefore, the source enrichment (metasomatism) of both these pipes is
attributed to the volatile- and K-rich, extremely low-viscosity melts that leak continuously to semi-continuously from the
asthenosphere and accumulate in the overlying lithosphere. Lithospheric/crustal extension, rather than decompression melting
induced by a mantle plume, is favoured as the cause of melting of the source regions of Majhgawan and Hinota pipes. This paper
is a review of the critical evaluation of the published work on these pipes based on contemporary knowledge derived from similar
occurrences elsewhere. 相似文献
4.
右江褶皱带地处扬子陆块和华夏陆块的结合部位,区内广泛发育以基性-超基性岩墙群和超酸性岩脉为主的燕山晚期双峰式岩浆活动。对桂中都安地区的金云钾镁煌斑岩脉进行了金云母~(40)Ar/~(39)Ar法测年,斑晶和基质金云母样品均给出了较一致的坪年龄,分别为93.6±0.6Ma和92.9±0.6Ma,相应的等时线年龄分别为93.4±0.9Ma和92.7±0.8Ma,上述年龄代表了岩脉的侵位年龄。结合区内报道的同期年代学资料,进一步证明右江褶皱带及其周缘晚白垩世双峰式岩浆活动响应了华南地区燕山晚期的构造转换事件及随后大规模的岩石圈伸展减薄。 相似文献
5.
贵州镇远地区钾镁煌斑岩产出控制因素浅析 总被引：6，自引：0，他引：6
贵州镇远马坪钾镁煌斑岩为我国发现的第一个含原生金刚石的钾镁煌斑岩,其时代为加里东中期。根据区内当时沉积建造的特点,结合钾镁煌斑岩常包含早期捕虏体的情况,尤其是区内钾镁煌斑岩主要产于加里东期北东向背斜构造翼部拐点范围的事实,认为区内钾镁煌斑岩的侵位应发生在加里东期沉积建造结束褶皱构造开始时刻。加里东构造运动先是沉积建造的塑性变形褶皱造山,岩层能干化后才开始发育大量断裂构造。纵弯褶皱在挤压作用背景下,因褶皱拐点存在拉伸和剪切的应力而构成透入性构造软弱部位,被深部岩浆热力所突破而成为上涌侵位及喷发通道。区域上,四堡期东西向基底断裂构造控制区内钾镁煌斑岩东西向带状分布,而加里东期褶皱及其拐点控制钾镁煌斑岩体(群)的产出,因此金刚石的找矿勘查应主要在有金刚石找矿信息的褶皱构造拐点范围开展。 相似文献
6.
Philip E. Wannamaker Jeffrey B. Hulen Matthew T. Heizler 《Journal of Volcanology and Geothermal Research》2000,96(3-4)
Newly discovered olivine phlogopite lamproite dikes intrude Jurassic siliciclastic strata in the Green River Desert subregion of the western Colorado Plateau tectonic province in southeastern Utah. The dikes yield an age of 22 Ma both from 40Ar/39Ar step-heating of phlogopite and from isochron modeling of laser-fused sanidine. This age is similar to those of mica-rich minettes and melanephelinites of the Wasatch Plateau about 125 km northwest and within the age range of the Navajo potassic volcanic field about 150 km to the southeast. The dikes intruded a pre-existing, northwest-oriented fracture system containing previously introduced bitumen, indicating that some regional lineaments of this trend are Early Miocene or older. The dikes are highly LREE-enriched, and display lamproite-specific REE ratios and phlogopite and sanidine compositions. Incompatible element and radiogenic isotope (Nd–Sr–Pb) ratios suggest that lithospheric source material modified by ancient subduction processes, together with younger asthenospheric source components, produced the melt. Timing of the intrusion coincides with the transition from Early–Middle Cenozoic, calc-alkaline plutonism to the dominantly mafic, Basin and Range type volcanism of the Late Cenozoic. While the lamproite occurrence indicates thermal input from the mantle, model non-uniqueness for both magma source depths and geophysical structure prevents quantitative comparison of Early Miocene with present-day lithospheric thickness. 相似文献
7.
It was shown that the crystal morphology, content, and size of diamonds depend on the concentrations of silica, magnesium, calcium, and carbon dioxide in the host kimberlites and lamproites. The character of this dependence suggests that the viscosity of the initial melts of these rocks was the main control of the morphology and properties of diamond crystals and indicates a magmatic genesis for this mineral. Two genetic varieties of diamond crystals were distinguished: larger residual grains coeval with the formation of the sources of kimberlite and lamproite magmas during the slow high-pressure fractionation of the near-bottom peridotite layer of the global magma ocean and smaller early magmatic grains, which crystallized during the decompression-friction transformation of kimberlite and lamproite protoliths into magmas. 相似文献
8.
Yongfeng Zhu Yoshihide Ogasawara T. Ayabe 《Journal of Volcanology and Geothermal Research》2002,116(1-2)
Kokchetav ‘lamproite’ occurs in the east end of Kokchetav massif and consists of phenocryst (mainly clinopyroxene) and matrix (mainly feldspar). The compositions of clinopyroxene, magnetite and biotite phenocryst were determined using wavelength dispersive spectrometry on a JEOL Super-probe 8900 electron microprobe for the purpose of revealing the process of magma evolution. Analyses revealed a core–rim variation, which is consistent with three stages of magmatic evolution: Mg-rich clinopyroxene cores (diopside) and biotite cores (phlogopite) crystallized in a deep magma chamber (stage I); Fe-rich clinopyroxene rim (salite) and biotite rim crystallized at low pressure in a shallow magma chamber (stage II); Magnetite phenocryst core also crystallized in a shallow magma chamber, and co-exists with Fe-rich clinopyroxene rim and biotite rim. The magnetite rims probably formed during magma eruption at the same time when groundmass crystallized (stage III). The calculated temperatures for ilmenite–magnetite pair range from 679 to 887°C, log fO2 values range from −11.1 to −14.9 log units. These values represent the latest conditions of magma as ilmenite exsolution in magnetite probably occurred during magma eruption from the shallow chamber to surface. 相似文献
9.
湖南宁乡钾镁煌斑岩中火山微球粒的初步研究 总被引：3，自引：0，他引：3
本次研究从钾镁煌斑岩中挑选出上万个微球粒进行了系统研究。微球粒有三种：无磁性无色透明—半透明浅黄色、棕褐色至不透明黑色；弱磁性—强磁性黑色；强磁性钢灰色铁质。除微球粒外，还有岩浆溅射碎片和炉渣伏溅射碎片等火山尘。微球粒具有火山喷发条件下可出现的多种多样的表面结构和内部结构。其化学成分主要为：（１）贫铁型，富Ｓｉ、Ｍｇ、Ｃａ、Ｐ，贫Ｔｉ、Ｍｎ、Ｋ；（２）富铁型，富Ｓｉ、Ｔｉ、Ｍｎ、Ｋ，贫Ｃａ、Ｍｇ、Ｐ；（３）高铁型，以Ｆｅ为主。单个微球粒中还出现高Ｓｉ相和高Ｓｉ、Ｍｇ相。据微球粒化学成分的多样性推测，在钾镁煌斑岩浆侵位至地壳深部环境下，经历过液态熔离作用，当火山喷发时，在快速冷凝条件下形成火山微球粒。 相似文献
10.
贵州白坟钾镁煌斑岩中钾碱镁闪石的研究 总被引：1，自引：0，他引：1
本文简要总结了近年有关钾镁煌斑岩的定义、矿物学及其地球化学研究的成果；讨论了钾碱镁闪石在钾镁煌斑岩研究中的意义；回顾了钾碱镁闪石的词源及其分类定名方法，详细介绍了贵州镇远地区白坟岩带中钾碱镁闪石的矿物学特征及其成分特征。 相似文献