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81.
82.
ZHAO Lei HAO Jinhu DING Yifei LIU Yulong China University of Geosciences 《《地质学报》英文版》2004,78(1):118-120
Based on studies of petrography, mineralogy and mineral chemistry, deep mantle fluids and their products in kimberlites and diamonds can be assorted into the ultradeep fluid-transmitted minerals with an oxygen-free feature, the deep fluid metasomatized-minerals characterized by enrichment in TiO2, K2O, BaO, REE and Fe3+, and the deep fluid-reformed minerals. The three types show a successive descent in fluid origin depth and metasomatism strength, and they have brought forth a series of corresponding metasomatic products. 相似文献
83.
X射线粉晶衍射仪在山东蒙阴金伯利岩蚀变矿物鉴定中的应用 总被引:5,自引:4,他引:1
山东蒙阴金伯利岩组成矿物以蚀变矿物为主,X射线粉晶衍射仪鉴定结果显示无矿金伯利岩矿物组分为方解石、白云石、石英、钙锆钛矿,标志性矿物为白云石和钙锆钛矿;贫矿金伯利岩矿物组分为蛇纹石、方解石、钙铝榴石、磁铁矿和金云母,标志性矿物为钙铝榴石;富矿金伯利岩矿物组分为蛇纹石、方解石、绿泥石、磷灰石、磁铁矿和金云母,标志性矿物为绿泥石和磷灰石。采用X射线粉晶衍射仪鉴定金伯利岩蚀变矿物组合,寻找蚀变矿物组分变化与金伯利岩含矿性的关系,利用标志性的蚀变矿物判断金伯利岩无矿、贫矿还是富矿,是非常有意义的。 相似文献
84.
Post-emplacement serpentinization and related hydrothermal metamorphism in a kimberlite from Venetia, South Africa 总被引:2,自引:0,他引:2
G. R. STRIPP M. FIELD J. C. SCHUMACHER R. S. J. SPARKS G. CRESSEY 《Journal of Metamorphic Geology》2006,24(6):515-534
The common serpentine–diopside matrix assemblage in volcaniclastic kimberlite (VK) at the Venetia Mine, South Africa is ascribed to a secondary origin, because of post‐emplacement serpentinization and associated hydrothermal metamorphism. Volcaniclastic deposits with 20–30% porosity infill kimberlite pipes in the waning stages of kimberlite eruptions. Olivine macrocrysts are typically rimmed by talc and are pseudomorphed by lizardite, with minor magnetite. The fine matrix consists of mixtures of lizardite, chlorite, smectite, brucite, calcite, titanite and andradite, an assemblage which either pseudomorphed microcrysts or in‐filled voids. Locally we recognize microcryst pseudomorphs rich in sub‐microscopic mixtures of lizardite with smectite, and other microcryst pseudomorphs and void‐filling matrix rich in chlorite and lizardite. Interstitial lizardite and associated phyllosilicates (brucite, smectite and chlorite) crystallized progressively from meteoric or hydrothermally derived pore waters, and Si4+ and Mg2+ released into the fluid phase during serpentinization of olivine macrocrysts. Radial‐fibrous fringes of diopside microlites around crystals display void‐filling textures because of unrestricted growth into pore spaces. Secondary diopside is attributed to Si4+, Mg2+ and Ca2+ cations released into the fluid phase by interaction with olivine, calcite and plagioclase in siliceous xenoliths. The paucity of primary, fine‐grained groundmass phases resistant to alteration, for example, perovskite and spinel, precludes an origin for the intergrain matrix as altered interstitial ash, glass or a late‐stage kimberlite melt. Isovolumetric replacement of olivine results in a volume increase of 60% so that pore spaces in the original deposit can be easily filled up with serpentine. The source of Al3+ to form chlorite and smectite is attributed to alteration of plagioclase in xenoliths which comprise 20–30 vol.% of the deposit. Titanite, hydro‐andradite and second‐generation diopside precipitate as hydrothermal minerals from calcium‐bearing serpentinizing fluids in replacement reactions and as void‐filling minerals. Consideration of mineral equilibria in the CaO‐MgO‐SiO2‐H2O‐CO2 system constrains the common matrix assemblage of lizardite and diopside in XCO2)–T space. At 300 bar, the assemblage is stable only at temperatures below 370 °C and XCO2 < 0.01. This upper limit on temperature is well below the plausible solidus of ultrabasic magmas. Furthermore, the requirement of trace CO2 in the fluid phase implies a post‐emplacement external source rather than ‘autometamorphism’ from kimberlite‐derived fluids, because of high PCO2 commonly inferred for kimberlite magmas. 相似文献
85.
Ravi Shanker S. Nag A. Ganguly A. Absar B. P. Rawat G. S. Singh 《Journal of Earth System Science》2001,110(1):63-76
The diamond bearing pipe rocks in Majhgawan-Hinota (more than four pipes) occur as intrusives in sandstones of Kaimur Group.
These Proterozoic (974 ±30-1170 ±20 Ma) intrusive rocks, occupying the southeastern margin of Aravalli craton, were called
as ‘micaceous kimberlite’ in tune with the reported kimberlite occurrences from other parts of the world. Judging from the
definition of kimberlite, as approved by the IUGS Subcommission on Systematics of Igneous Rocks, it is not justified to call
these rocks as ‘micaceous kimberlite’. Rather the mineralogical assemblages such as absence of typomorphic mineral monticellite
(primary), abundance of phlogopite cognate, frequent presence of barite and primary carbonate mostly as calcite coupled with
ultrapotassic and volatile-rich (dominantly H2O) nature and high concentration of incompatible elements (such as Ba, Zr, Th, U), low Th/U ratios, low REE and no Eu-anomaly
clearly indicate a close similarity with that of South African orangeites. Thus orangeites of Proterozoic age occur outside
the Kaapvaal craton of South Africa which are much younger (200 Ma to 110 Ma) in age. 相似文献
86.
87.
山东和辽宁金伯利岩的稀土元素地球化学特征 总被引:4,自引:0,他引:4
山东和辽宁金伯利岩的稀土元素球粒陨石标准化曲线均向右倾斜,(La/Yb)N比值为22.7—357.9,LREE/HREE比值12.4—61.3,为轻稀土富集型。含金刚石较富的金伯利岩∑REE变化范围较小,多集中在300—600ppm之间;贫(无)矿金伯利岩∑REE变化范围较大,大多数为低于300ppm或高于600ppm。所以金伯利岩∑REE在寻找金刚石中可以作为重要的参考数据。金伯利岩深源捕虏体的REE含量低,如山东金伯利岩捕虏体∑REE237.6ppm,河北和辽宁的榴辉岩分别为55.2ppm和73.3ppm,山东的纯橄岩捕虏体∑REE最低,仅10.6ppm。 相似文献
88.
本文报道了我国山东蒙阴金伯利岩中蒙山矿的一些研究成果。作者在该区采集的蒙山矿与锶钛铁矿-镧铀钛铁矿族(Crichtonite-davite group)矿物等结构和成分介于钡蒙山矿(lindsleyite)与蒙山矿(mathiasite)之间,其BaO含量为2.13—2.89wt%,K_2O含量为0.75—1.27wt%,K/Ba原子比为0.898—1.938;特别富Cr_2O_3、ZrO_2和LREE_2O_3。本文还阐述了山东蒙山矿的类质同象和晶体结构特点,讨论其对地幔交代作用研究的启示。 相似文献
89.
笔者在代表金伯利质熔浆结晶演化产物的橄榄石巨斑、金云母斑晶和磷灰石粗晶中首次发现了岩浆包裹体。捕晶角闪石、单斜辉石及橄榄石中岩浆包裹体研究证实,其源于基性-超基性杂岩。依据充填物相态和成分,将本区岩浆包裹体划分为两类:A,硅酸盐熔融包裹体;B,流体熔融包裹体,前者又细分出一个亚类(A′),即晶体-玻璃包裹体。经岩浆包裹体均一化温度值的测定和压力估算,原始金伯利质熔浆晶出巨斑橄榄石的温度略高于1116℃,压力约4.5GPa。 相似文献
90.