Anhydrous and water-saturated melting experiments of an olivine andesite from Mt Yakushi-Yama, northeastern Shikoku, Japan     

Toshisuke  Kawasaki Koji  Okusako Toshihiro  Nishiyama 《Island Arc》1993,2(4):228-237

Abstract Melting experiments have been carried out on an olivine andesite of Mt Yakushi-Yama from the Miocene Setouchi volcanic belt in northeastern Shikoku, Japan. This andesite has been characterized by a low ratio of FeO*/Mg° (= 0.78). Phase relations have been determined within the pressure range of 2.8 to 19.3 kbar at 1000-1300°C under anhydrous and water-saturated conditions. At pressures less than 8.8 kbar, olivine is a liquidus phase. Orthopyroxene appears on the liquidus at 9.3 kbar under the anhydrous conditions. The multiple saturation point rises up to 17.5 kbar for water-saturated experiments. The andesite melt coexists with olivine and orthopyroxene just below the liquidus at 8.8–9.3 kbar and 1230°C for dry conditions, and at 17.5 kbar and 1060°C under water-saturated conditions. These experimental results indicate that the Yakushi-Yama olivine andesite magma could coexist with a harzburgitic mantle at depths between about 30 and 60 km, and at temperatures between 1060 and 1230°C. Experimental data also suggest a possibility that a high magnesian andesite magma would be generated by a direct partial melting of the uppermost harzburgitic mantle under anhydrous conditions.  相似文献   

Variations in Melt Productivity and Melting Conditions along SWIR (70{degrees}E-49{degrees}E): Evidence from Olivine-hosted and Plagioclase-hosted Melt Inclusions   总被引：1，自引：0，他引：1  

Font  L.; Murton  B. J.; Roberts  S.; Tindle  A. G. 《Journal of Petrology》2007,48(8):1471-1494

Melt inclusion and host glass compositions from the easternend of the Southwest Indian Ridge show a progressive depletionin light rare earth elements (LREE), Na₈ and (La/Sm)_n, but anincrease in Fe₈, from the NE (64°E) towards the SW (49°E).These changes indicate an increase in the degree of mantle meltingtowards the SW and correlate with a shallowing of the ridgeaxial depth and increase in crustal thickness. In addition,LREE enrichment in both melt inclusions and host glasses fromthe NE end of the ridge are compatible with re-fertilizationof a depleted mantle source. The large compositional variations(e.g. P₂O₅ and K₂O) of the melt inclusions from the NE end ofthe ridge (64°E), coupled with low Fe₈ values, suggest thatmelts from the NE correspond to a variety of different batchesof melts generated at shallow levels in the mantle melting column.In contrast, the progressively more depleted compositions andhigher Fe₈ values of the olivine- and plagioclase-hosted meltinclusions at the SW end of the studied region (49°E), suggestthat these melt inclusions represent batches of melt generatedby higher degrees of melting at greater mean depths in the mantlemelting column. Systematic differences in Fe₈ values betweenthe plagioclase- and the olivine-hosted melt inclusions in theSW end (49°E) of the studied ridge area, suggest that theplagioclase-hosted melt inclusions represent final batches ofmelt generated at the top of the mantle melting column, whereasthe olivine-hosted melt inclusions correspond to melts generatedfrom less depleted, more fertile mantle at greater depths. KEY WORDS: basalt; melt inclusions; olivine; plagioclase; Southwest Indian Ridge  相似文献   

新疆二红洼镁铁—超镁铁岩体橄榄石成因及其对硫化物熔离的指示     

孙涛  钱壮志  张瑞  张江江  姜超  杨素红  王若梅 《地质学报》2014,88(8):1494-1503

二红洼岩体位于新疆东天山黄山镁铁—超镁铁岩带的西段,地表由南、北两个小岩体组成,北岩体出露面积约1.42km2,呈北东—南西向展布;南岩体在呈椭圆形,出露面积约为6.25km2。岩体可分为两个侵入期次:第一侵入期次岩性为(含长)二辉橄榄岩和橄榄辉长岩,第二侵入期次岩性为辉长苏长岩和淡色辉长岩,辉长苏长岩侵入于第一期次形成的含长二辉橄榄岩和橄榄辉长岩中。岩体橄榄石Fo值在80.9~89.7之间,为贵橄榄石;Ni含量变化范围较大,主要集中在102.19×10-6~4319.66×10-6之间。岩体母岩浆MgO含量为10.3%,FeO含量为10.8%;回归计算结果显示二红洼岩体的原始岩浆中MgO含量为15.73%,FeO含量为10.71%。在橄榄石的结晶过程中母岩浆达到硫饱和,并发生有硫化物的熔离作用;橄榄石与硫化物的晶出质量比(橄榄石:硫化物)为50~100∶1。通过岩石学、矿物学特征以及模拟计算结果表明,二红洼岩体具有形成铜镍矿床的基本条件,但是岩体在深部岩浆房已经达到硫饱和并发生了硫化物的熔离作用,导致母岩浆中亏损Ni、Cu等成矿元素,未能形成工业矿体;在以后找矿勘探中,需要寻找早期硫化物熔离所形成的那部分硫化物熔体,并进一步寻找成矿富集的有利地段。  相似文献   

Standard electrical conductivity of isotropic, homogeneous olivine in the temperature range 1200°-1500°C     

T. J. Shankland  A. G. Duba 《Geophysical Journal International》1990,103(1):25-31

  相似文献   

Continuous reactions with amphibole, garnet and plagioclase     

A. J. ZINGG 《Journal of Metamorphic Geology》1995,13(3):431-443

Abstract End-member, continuous and degenerate reactions are derived for the multisystem with the six components Na₂O, CaO, (Mg/Fe)O, Al₂O₃, SiO₂, H₂O among the phases plagioclase_ss, garnet_ss, amphibole_ss, cpx, opx, olivine, spinel, quartz and an aqueous fluid. The chemography of this system is degenerate due to the co-linearity 2Opx = Ol + Qtz. This co-linearity has its implications both on reaction space and phase equilibria. From a total of 28 reaction systems, reaction space is derived for nine subsystems (phases in parentheses are absent): Case A₁: (Cpx,Ol) (Cpx,Opx) and (Cpx,Qtz), Case A₂: (Spl,Ol) (Spl,Opx) and (Spl,Qtz), Case B: (Ol,Opx) (Ol,Qtz) and (Opx,Qtz). In the absence of either cpx or spl (case A), three reactions form an invariant point, either [Cpx] or [Spl], where the co-linear phases olivine, opx and quartz coexist on the transformation line 2Opx = Ol + Qtz. Changing mineral compositions force invariant points to move along the line with the different reaction curves changing their relative position according to Schreinemakers’rules. Zero contours, i.e. the location where (a) phase(s) disappear(s) in reaction space correspond to singular points in phase diagrams. Two types are distinguished; singular points of indispensable and of substitutable phases. In the first case the phase disappears from the entire bundle while in the second it disappears from a single reaction. In the specific case where the substitutable phases are also the co-linear ones, two of the three co-linear phases disappear simultaneously. Two of the three reaction curves coincide. In the system including Cpx and Spl (Case B) three reactions, (Ol,Opx) (Ol,Qtz) and (Opx,Qtz), oppose three invariant points, [Ol], [Opx] and [Qtz]. Invariant points no longer move along the line 2Opx = Ol + Qtz. The coincidence of the zero contours of all three co-linear phases in reaction space-the result of the chemographic degeneracy-causes the respective singular points to coincide in the phase diagrams. This is the location where curves must be rearranged in a bundle to conform Schreinemakers’rules. The reaction Grs₁Prp₂= 2 Ol + An is fourth order degenerate and part of all nine subsystems (cases A and B). It can be used to relate the different phase diagrams to one another.  相似文献   

FTIR Spectrum of Phenocryst Olivine as an Indicator of Silica Saturation in Magmas   总被引：3，自引：0，他引：3  

MATVEEV  S.; PORTNYAGIN  M.; BALLHAUS  C.; BROOKER  R.; GEIGER  C. A. 《Journal of Petrology》2005,46(3):603-614

Fourier Transform infrared (FTIR) absorption spectra of hydroxylwere measured on olivine phenocrysts from hydrous basaltic meltsthat originated in island-arc tectonic settings. The basalticmelts encompass a wide range of silica activities from orthopyroxene-saturatedhypersthene-normative to nepheline-normative compositions. Theintensities and wavenumber placement of hydroxyl absorptionbands correlate with the degree of silica saturation of theparent melt from which the olivine crystallized. Olivines fromsilica-undersaturated nepheline-normative melts absorb IR radiationin the wavenumber range 3430–3590 cm^–1 (Group 1).In contrast, olivines from orthopyroxene-saturated boniniticmelts exhibit hydroxyl absorption bands in the wavenumber range3285–3380 cm^–1 (Group 2). Olivines crystallizedat intermediate silica activities exhibit a combination of thetwo groups of hydroxyl IR bands, where the proportion of Group2 bands increases with increasing silica saturation of the parentmelt. The positions of hydroxyl absorption peaks observed herefor natural samples are consistent with previous measurementson experimentally annealed olivines. Thus protonation experimentscan be employed to make spectroscopically dry olivine structuresvisible by IR, yielding information on the silica saturationof the parental magmas. Hydroxyl concentrations in the studiedolivines were estimated to be 1–2 ppm, corresponding toan olivine–melt partition coefficient of (1·0 ±0·3) x 10^–4. KEY WORDS: nominally anhydrous minerals; olivine; water; mantle; silica activity; melt inclusions  相似文献   

Amoeboid olivine aggregates and related objects in carbonaceous chondrites: records of nebular and asteroid processes     

Alexander N. Krot  Michail I. Petaev  Shoichi Itoh  Timothy J. Fagan  Hisayoshi Yurimoto  Michael K. Weisberg  Matsumi Komatsu  Klaus Keil 《Chemie der Erde / Geochemistry》2004,64(3):185-239

Amoeboid olivine aggregates (AOAs) are the most common type of refractory inclusions in CM, CR, CH, CV, CO, and ungrouped carbonaceous chondrites Acfer 094 and Adelaide; only one AOA was found in the CB_b chondrite Hammadah al Hamra 237 and none were observed in the CB_a chondrites Bencubbin, Gujba, and Weatherford. In primitive (unaltered and unmetamorphosed) carbonaceous chondrites, AOAs consist of forsterite (Fa_<2), Fe, Ni-metal (5-12 wt% Ni), and Ca, Al-rich inclusions (CAIs) composed of Al-diopside, spinel, anorthite, and very rare melilite. Melilite is typically replaced by a fine-grained mixture of spinel, Al-diopside, and ±anorthite; spinel is replaced by anorthite. About 10% of AOAs contain low-Ca pyroxene replacing forsterite. Forsterite and spinel are always ¹⁶O-rich (δ^17,18O∼−40‰ to −50‰), whereas melilite, anorthite, and diopside could be either similarly ¹⁶O-rich or ¹⁶O-depleted to varying degrees; the latter is common in AOAs from altered and metamorphosed carbonaceous chondrites such as some CVs and COs. Low-Ca pyroxene is either ¹⁶O-rich (δ^17,18O∼−40‰) or ¹⁶O-poor (δ^17,18O∼0‰). Most AOAs in CV chondrites have unfractionated (∼2-10×CI) rare-earth element patterns. AOAs have similar textures, mineralogy and oxygen isotopic compositions to those of forsterite-rich accretionary rims surrounding different types of CAIs (compact and fluffy Type A, Type B, and fine-grained, spinel-rich) in CV and CR chondrites. AOAs in primitive carbonaceous chondrites show no evidence for alteration and thermal metamorphism. Secondary minerals in AOAs from CR, CM, and CO, and CV chondrites are similar to those in chondrules, CAIs, and matrices of their host meteorites and include phyllosilicates, magnetite, carbonates, nepheline, sodalite, grossular, wollastonite, hedenbergite, andradite, and ferrous olivine.Our observations and a thermodynamic analysis suggest that AOAs and forsterite-rich accretionary rims formed in ¹⁶O-rich gaseous reservoirs, probably in the CAI-forming region(s), as aggregates of solar nebular condensates originally composed of forsterite, Fe, Ni-metal, and CAIs. Some of the CAIs were melted prior to aggregation into AOAs and experienced formation of Wark-Lovering rims. Before and possibly after the aggregation, melilite and spinel in CAIs reacted with SiO and Mg of the solar nebula gas enriched in ¹⁶O to form Al-diopside and anorthite. Forsterite in some AOAs reacted with ¹⁶O-enriched SiO gas to form low-Ca pyroxene. Some other AOAs were either reheated in ¹⁶O-poor gaseous reservoirs or coated by ¹⁶O-depleted pyroxene-rich dust and melted to varying degrees, possibly during chondrule formation. The most extensively melted AOAs experienced oxygen isotope exchange with ¹⁶O-poor nebular gas and may have been transformed into magnesian (Type I) chondrules. Secondary mineralization and at least some of the oxygen isotope exchange in AOAs from altered and metamorphosed chondrites must have resulted from alteration in the presence of aqueous solutions after aggregation and lithification of the chondrite parent asteroids.  相似文献   

Deformation microstructures of olivine in peridotite from Spitsbergen, Svalbard and implications for seismic anisotropy   总被引：1，自引：0，他引：1  

H. JUNG  W. MO  S. H. CHOI 《Journal of Metamorphic Geology》2009,27(9):707-720

To understand the deformation mechanism and seismic anisotropy in the uppermost mantle beneath Spitsbergen, Svalbard, in the Arctic, the deformation microstructures of olivine in the peridotite of Spitsbergen were studied. Seismic anisotropy in the upper mantle can be explained mainly by the lattice-preferred orientation (LPO) of olivine. The LPOs of the olivine in the peridotites were determined using electron backscattered diffraction patterns. Eight specimens out of 10 showed that the [100] axis of the olivine was aligned subparallel to the lineation and that the (010) plane was subparallel to the foliation, showing a type A LPO. In the other two specimens the [100] axis of olivine was aligned subparallel to the lineation and both the [010] and [001] axes were distributed in a girdle nearly perpendicular to the lineation, showing a type D LPO. The dislocation density of the olivine in the samples showing a type D LPO was higher than that in the samples showing a type A LPO. The result of an Fourier transformation infrared study showed that both the types A and D samples were dry. These observations were in good agreement with a previous experimental study ( Tectonophysics , 421 , 2006, 1 ): samples showing a type D LPO for olivine were observed at a high stress condition and samples showing both types A and D LPO were deformed under dry condition. Observations of both strong LPOs and dislocations of olivine indicate that the peridotites studied were deformed by dislocation creep. The seismic anisotropy calculated from the LPOs of the olivine could be used to explain the seismic anisotropy of P - and S -waves in the lithospheric mantle beneath Spitsbergen, Svalbard.  相似文献   

电子背散射衍射和傅里叶变换红外光谱结合测量橄榄石的原位含水量          下载免费PDF全文

闫浩洁  王勤 《高校地质学报》2018,24(1):1

橄榄石的含水量对上地幔的物理化学性质具有重要影响。傅里叶变换红外光谱（简称FTIR） 是目前最常用的测量名 义上无水矿物含水量的方法。由于矿物中红外光谱的吸收系数是各向异性的,理论上应使用偏振光来测量橄榄石的含水 量,但是该方法需要把橄榄石颗粒分离出来进行定向,非常费时。前人大多使用非偏振光来测量薄片中多个橄榄石的含水 量,并使用Paterson （1982） 的校正方法计算样品中橄榄石的平均含水量。非偏振光的使用忽略了颗粒定向造成的影响,会 低估橄榄石的含水量。上地幔橄榄石常发育晶格优选定向,为快速准确地获得橄榄石的原位含水量,该文将电子背散射衍 射技术（EBSD） 与FTIR 相结合,提出测量薄片中橄榄石含水量的新方法。首先使用Bell 等（2003） 的红外偏振光实验结 果,通过橄榄石[100]、[010]和[001]方向的含水量吸收系数建立一个椭球体。然后使用EBSD 测量某一颗粒在薄片中的取 向,根据欧拉角计算该方向的含水量吸收系数Ws,再根据Beer-Lambert 公式获得该颗粒的含水量。对加拿大Slave 克拉通 Muskox 金伯利岩携带的石榴橄榄岩中橄榄石的含水量研究表明,该方法可用于测量显微尺度的橄榄石原位含水量分布,为 橄榄石含水量与组构关系的研究提供基础资料。  相似文献   

大麻坪橄榄石冲击波实验研究与高压态物态方程参数的确定          下载免费PDF全文

陈祖安  袁贤昊  黄晓葛  刘福生  地力夏提  白武明 《地球物理学报》2016,59(1):152-156

利用冲击波进行的动高压实验对研究超高压下的物质性质也是十分有效的.本文报告了对大麻坪采集的橄榄石进行压力在10~45GPa范围的冲击波动高压实验结果.结合前人等温冷压实验结果,确定了实验过程的温度,对于冲击波实验压力从10GPa变化到30GPa时,温度在摄氏几十度到摄氏800多度之间.测量了岩石超高压下密度变化,在3.627~4.009g·cm~(-3)之间.通过回收实验和确定的温度,表明小于30GPa压力实验条件下,没有发生相变过程.同时也确定了状态方程的参数.最后,指出了实验结果在上地幔地球内部物质运动过程的含义,即冷板块中的亚临界橄榄岩可以存在地幔转换带中.  相似文献