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131.
南平花岗伟晶岩中铯沸石的研究 总被引:5,自引:0,他引:5
目前在中国已发现两种铯矿物,即南平石和铯沸石,其中铯沸石主要分布在新疆、陕西、河南省的花岗伟晶岩中,在华南,南平花岗伟晶岩是迄今所报道的铯沸石的唯一产地。我们将南平钩沸石分成原生和次生两类,本文详细报道了南平铯沸石的产状、物性和光性、化学成分、X射线衍射特征、红外光谱、差热分析和形成过程。 相似文献
132.
133.
地幔地球化学研究综述 总被引:2,自引:0,他引:2
系统地介绍了近二十年来地幔地球化学在全球及区域地幔平均化学组成,地幔的化学不均一性及区域太产分布,地幔交代作用,化学地球动力学,地幔物理化学环境等五个方面的研究现状与进展。 相似文献
134.
伊通地堑上地幔剪切带 总被引:3,自引:1,他引:3
通过研究糜棱岩型幔源包体的变形显微构造、位错亚构造及组构特征,确定它是上地幔剪切带的代表物质。该带形成温度为729~828℃、压力为1.10~1.38GPa、差异应力为97~150MPa、应变速率为IO ̄(-14)~1O ̄(-12)s ̄(-1)、等效粘滞度为10~1000EPa·s和深度为37~45km。这是一种与地幔底辟作用有关的规模较小的缓倾斜剪切带,也是应变集中带,能导致上地幔地震波速各向异性,并与地震活动有关 相似文献
135.
横断山不同成因类型花岗岩类岩石中黑云母的标型特征 总被引:8,自引:5,他引:8
本文研究了横断山区不同成因类型花岗岩类岩石中黑云母的化学成分、微量元素、结构和物理性质等。结合花岗岩类岩石的成因类型,将黑云母分为三个亚种:富镁黑云母(MF=1.3—1.5)、镁黑云母(MF=1—1.3)和富铁黑云母(MF=0.5-1)。 相似文献
136.
Sonja Aulbach William L. Griffin Norman J. Pearson Suzanne Y. O’Reilly Buddy J. Doyle 《Contributions to Mineralogy and Petrology》2007,154(4):409-427
Major-element compositions of minerals in peridotite xenoliths from the Lac de Gras kimberlites provide constraints on the
mode of lithosphere formation beneath the central Slave Craton, Canada. Magnesia contents of reconstructed whole rocks correlate
positively with NiO and negatively with CaO contents, consistent with variable partial melt extraction. Alumina and Cr2O3 contents are broadly positively correlated, suggestive of melt depletion in the absence of a Cr–Al phase. Garnet modes are
high at a given Al2O3 content (a proxy for melt depletion), falling about a 7 GPa melt depletion model. These observations, combined with high
olivine Mg# and major-element relationships of FeO-poor peridotites (<7.5 wt%) indicative of melt loss at pressures >3 GPa
(residual FeO content being a sensitive indicator of melt extraction pressure), and similar high pressures of last equilibration
(∼4.2 to 5.8 GPa), provide multiple lines of evidence that the mantle beneath the central Slave Craton has originated as a
residue from high-pressure melting, possibly during plume subcretion. Apparent low melt depletion pressures for high-FeO peridotites
(>7.5 wt%) could suggest formation in an oceanic setting, followed by subduction to their depth of entrainment. However, these
rocks, which are characterised by low SiO2 contents (<43 wt%), are more likely to be the result of post-melting FeO-addition, leading to spuriously low estimates of
melt extraction pressures. They may have reacted with a silica-undersaturated melt that dissolved orthopyroxene, or experienced
olivine injection by crystallising melts. A secular FeO-enrichment of parts of the deep mantle lithosphere is supported by
lower average Mg# in xenolithic olivine (91.7) compared to olivine inclusions in diamond (92.6). 相似文献
137.
We have conducted high-pressure experiments on a natural oceanic gabbro composition (Gb108). Our aim was to test recent proposals
that Sr-enrichment in rare primitive melt inclusions from Mauna Loa, Hawaii, may have resulted from melting of garnet pyroxenite
formed in the magma source regions by reaction of peridotite with siliceous, Sr-enriched partial melts of eclogite of gabbroic
composition. Gb108 is a natural, Sr-enriched olivine gabbro, which has a strong positive Sr anomaly superimposed on an overall
depleted incompatible trace element pattern, reflecting its origin as a plagioclase-rich cumulate. At high pressures it crystallises
as a coesite eclogite assemblage, with the solidus between 1,300 and 1,350°C at 3.5 GPa and 1,450 and 1,500°C at 4.5 GPa.
Clinopyroxenes contain 4–9% Ca-eskolaite component, which varies systematically with pressure and temperature. Garnets are
almandine and grossular-rich. Low degree partial melts are highly siliceous in composition, resembling dacites. Coesite is
eliminated between 50 and 100°C above the solidus. The whole-rock Sr-enrichment is primarily hosted by clinopyroxene. This
phase dominates the mode (>75 wt%) at all investigated PT conditions, and is the major contributor to partial melts of this
eclogite composition. Hence the partial melts have trace element patterns sub-parallel to those of clinopyroxene with ≈10×
greater overall abundances and with strong positive Sr anomalies. Recent studies of primitive Hawaiian volcanics have suggested
the incorporation into their source regions of eclogite, formerly gabbroic material recycled through the mantle at subduction
zones. The models suggest that formerly gabbroic material, present as eclogite in the Hawaiian plume, partially melted earlier
than surrounding peridotite (i.e. at higher pressure) because of the lower solidus temperature of eclogite compared with peridotite.
This produced highly siliceous melts which reacted with surrounding peridotite producing hybrid pyroxene + garnet lithologies.
The Sr-enriched nature of the formerly plagioclase-rich gabbro was present in the siliceous partial melts, as demonstrated
by these experiments, and was transferred to the reactive pyroxenite. These in turn partially melted, producing Sr-enriched
picritic liquids which mixed with normal picritic partial melts of peridotite before eruption. On rare occasions these mixed,
relatively Sr-rich melts were trapped as melt inclusions in primitive olivine phenocrysts.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
138.
Vadim S. Kamenetsky Andrey A. Gurenko 《Contributions to Mineralogy and Petrology》2007,153(4):465-481
The origin of compositional heterogeneities among the magmas parental to mid-ocean ridge basalts (MORB) was investigated using
a single rock piece of the olivine-phyric basalt from 43°N, Mid-Atlantic Ridge (AII D11-177). The exceptional feature of this
sample is presence of very primitive olivine crystals (90–91 mol% Fo) that are significantly variable in terms of CaO (0.15–0.35 wt%).
A population of low-Ca olivine (0.15–0.25 wt% CaO) is also notably distinct from high-Ca olivine population in AII D11-177,
and primitive MORB olivine in general, in having unusual assemblage of trapped mineral and glass inclusions. Mineral inclusions
are represented by high-magnesian (Mg# 90.7–91.1 mol%) orthopyroxene and Cr-spinel, distinctly enriched in TiO2 (up to 5 wt%, c.f. <1 wt% in common MORB spinel). Glass inclusions associated with orthopyroxene and high-Ti Cr-spinel have
andesitic compositions (53–58 wt% SiO2). Compared to the pillow-rim glass and “normal” MORB inclusions, the Si-rich glass inclusions in low-Ca olivine have strongly
reduced Ca and elevated concentrations of Ti, Na, K, P, Cl, and highly incompatible trace elements. Strong variability is
recorded among glass inclusions within a single olivine phenocrysts. We argue that the observed compositional anomalies are
mineralogically controlled, and thus may arise from the interaction between hot MORB magmas and crystal cumulates in the oceanic
crust or magma chamber. 相似文献
139.
Distribution of platinum-group elements in the Platreef at Overysel,northern Bushveld Complex: a combined PGM and LA-ICP-MS study 总被引:1,自引:0,他引:1
Detailed mineralogical and laser ablation-inductively coupled plasma-mass spectrometry studies have revealed the physical
manifestation of the platinum-group elements (PGE) within the Platreef at Overysel, northern Bushveld Complex, South Africa.
The PGE in the Platreef were originally concentrated in an immiscible sulfide liquid along with semi-metals such as Bi and
Te. As the sulfide liquid began to crystallize, virtually all the Os, Ir, Ru and Rh partitioned into monosulfide solid solution
(mss), which on further cooling, exsolved to form pyrrhotite and pentlandite with Os, Ir and Ru remaining in solid solution
in both phases with Rh prefentially partitioning into pentlandite. Platinum, some Pd and Au were concentrated in the residual
sulfide liquid after mss crystallization, and were then concentrated in an immiscible late stage melt along with semi metals,
which was expelled to the grain boundaries during crystallization of intermediate solid solution (iss) to form Pt and Pd tellurides
and electrum around the margins of the sulfide grains. Tiny droplets of this melt trapped in the crystallizing mss and iss
cooled to form Pt–Bi–Te microinclusions in all sulfide phases, whilst the excess Pd was accommodated in solid solution in
pentlandite. Minor redistribution and recrystallization by hydrothermal fluids occurred around xenoliths and at the very base
of the mineralized zone within the footwall, however, the overall lack of secondary alteration coupled with the volatile-poor
nature of the gneissic footwall have allowed the preservation of what may be the most ‘primary’ style of Platreef mineralization.
The lack of PGM inclusions within early liquidus phases suggests very early sulfur saturation in the Platreef, lending support
to theories involving S saturation occurring prior to intrusion of the Platreef, possibly within a staging chamber. 相似文献
140.