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1.
在温度为１１３０－１４５０℃，压力为０．４－２．０ＧＰａ条件下，实验研究了地幔橄榄岩部分熔融及相转变（尖晶石相→斜长石相）过程中的固相化学成分演变。在部分熔融中，随熔融度的增大，橄榄石的Ｍｇ／（Ｍｇ＋Ｆｅ）＾尖晶石和斜方辉石的Ｍｇ／（Ｍｇ＋Ｆｅ）及Ｃｒ／（Ｃｒ＋Ａｌ）逐渐增大；而橄榄石中的Ｃａ含量增至单斜辉石消失后逐渐降低；尖晶石中的Ｔｉ以较低的含量（ＴｉＯ２〈０．１５％）保持不变或稍有降低；斜方 相似文献
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地幔橄榄岩部分熔融及相转变（尖晶石相→斜长石相）过程中的固相化学成分演化──Ⅰ．实验研究 总被引：1，自引：0，他引：1
在温度为ｌｌ３０─ｌ４５０℃，压力为０．４─２．０ＧＰａ条件下，实验研究了地幔橄榄岩部分熔融及相转变（尖晶石相→斜长石相）过程中的固相化学成分演变。在部分熔融中，随熔融度的增大，橄榄石的Ｍｇ／（Ｍｇ＋Ｆｅ）尖晶石和斜方辉石的Ｍｇ／（Ｍｇ＋Ｆｅ）及Ｃｒ／（Ｃｒ＋Ａｌ）逐渐增大；而橄榄石中的Ｃａ含量增至单斜辉石消失后逐渐降低；尖晶石中的Ｔｉ以较低的含量（ＴｉＯ２＜０．１５％）保持不变或稍有降低；斜方辉石中的Ｔｉ含量及单斜辉石的Ｎａ和Ｔｉ含量逐渐降低，直至非常小的值。在从尖晶石橄榄岩向斜长石橄榄岩的相转变过程中，尖晶石强烈富Ｔｉ，且其Ｃｒ／（Ｃｒ＋Ａｌ）逐渐增大；斜方辉石中的Ｔｉ含量和Ｃｒ／（Ｃｒ＋Ａｌ）同时逐渐增大；单斜辉石中的Ｎａ含量降低而Ｔｉ含量升高或保持不变。当斜长石橄榄岩经受了部分熔融（即使很微弱），其在相转变过程中引起的各矿物相的化学成分特征要全部消失，而表现部分熔融作用的特征。这可作为判别橄榄岩在斜长石相域内是否经历了部分熔融的标志。关键词 相似文献
3.
分析了全球一些有代表性的上地幔尖晶石橄榄岩和斜长石橄榄岩中各矿物的化学成分变化特征。发现在斜长石橄榄岩中，尖晶石和斜方辉石富Ｔｉ，且Ｔｉ含量随Ｃｒ／（Ｃｒ＋Ａｌ）的增大而增大；单斜辉石富Ｔｉ贫Ｎａ，其Ｔｉ含量随Ｎａ含量的增大而减少。据此，结合实验结果，可以肯定世界各地大多数斜长石二辉橄榄岩在斜长石相域内未经受部分熔融。岩体所曾经受的部分熔融只发生在尖晶石或石榴石相。它们的相对熔融度可以用下面两个指标来估计：（１）最贫Ｔｉ尖晶石的Ｃｒ／（Ｃｒ＋Ａｌ）；（２）单斜辉石的最高Ｎａ含量。对于尖晶石橄榄岩，从二辉橄榄岩、方辉橄榄岩到纯橄榄岩，其尖晶石和斜方辉石的Ｃｒ／（Ｃｒ＋Ａｌ）逐渐增大，而含量很低的Ｔｉ或Ｎａ在尖晶石、斜方辉石及单斜辉石中保持不变或趋向逐渐减小。尖晶石橄榄岩的相对熔融度可据尖晶石的Ｃｒ／（Ｃｒ＋Ａｌ）和单斜辉石的Ｎａ含量来判断。 相似文献
4.
西秦岭寒武系金矿床中硅岩的地质地球化学特征及其沉积环境意义 总被引：31，自引：4，他引：27
西秦岭寒武系中的硅岩是拉尔玛－邛莫层控金矿床的主要赋矿岩石之一。含矿硅岩呈块状、条带状、层纹状、多孔状和同生角砾状等。硅岩单层厚度一般为３０～２００ｍ。主要成分ＳｉＯ２平均含量高达９５．３０％,其余为ＦｅＯ、Ｆｅ２Ｏ３和有机炭等。硅岩的Ａｌ／（Ａｌ＋Ｆｅ＋Ｍｎ）比值低于０．３（平均０．１５３）,投点于Ｆｅ／Ｔｉ－Ａｌ／（Ａｌ＋Ｆｅ＋Ｍｎ）图解和Ａｌ－Ｆｅ－Ｍｎ三角图解上,均落于热水沉积物区。硅岩中微量元素十分丰富,不仅含有具基性、超基性特征的元素群（如Ｃｕ、Ｃｒ、Ｐｔ、Ｐｄ、Ｏｓ等）,而且还含有具酸性特征的元素群（如Ｗ、Ｍｏ、Ｕ等）。硅岩中稀土以总量（３．２９～１００μｇ／ｇ）低和铈亏损为特征。经北美页岩标准化后的稀土比值随原子序数的增大而增大。硅岩的δ１８Ｏ值为１７．６０‰～２３．２４‰,据此得到它形成的温度为７０．９℃～１１８．１℃。硅岩的δ３０Ｓｉ值主要为＋０．４‰～＋０．８‰。上述硅岩的特点均显示其与喷流热水沉积作用有关。硅岩中Ｐ２Ｏ５含量、Ｓｒ／Ｂａ比值、δＣｅ值以及δ３０Ｓｉ值表明,它主要是在深海—半深海环境下形成的。 相似文献
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在山东蒙阴金伯利岩中，首次发现了沂蒙矿类质同象系列新的富Ｔｉ矿物（变）种。理想的晶体化学式可表达为：Ｋ（Ｔｉ５Ｆｅ３Ｃｒ２Ｍｇ２）１２Ｏ１９（简称Ｋ－Ｔｉ沂蒙矿）（Ｂａ，Ｋ）（Ｔｉ５Ｆｅ４Ｍｇ２Ｃｒ）１２Ｏ１９（简称Ｂａ－Ｔｉ沂蒙矿）从而与原来确定的沂蒙矿Ｋ（Ｃｒ５Ｔｉ３Ｆｅ２Ｍｇ２）１２Ｏ１９和钡钛铁铬矿（Ｂａ，Ｋ）（Ｃｒ４Ｆｅ４Ｔｉ３Ｍｇ）１２Ｏ１９ｇ一起构成了金伯利岩中ＡＭ１２Ｏ１９磁铁铅矿 相似文献
6.
碱性玄武岩中幔源岩石包体内尖晶石成分特征及其岩石学成因意义 总被引：4，自引：2，他引：2
通过对我国东部北起黑龙江省南至海南省３１个产地的新生代碱性玄武岩中橄榄岩类 （纯橄岩、方辉橄榄岩及二辉橄榄岩） 包体和辉石岩类包体中的１６０ 多个尖晶石电子探针分析数据, 论述了尖晶石的Ｃｒ－Ａｌ, Ｆｅ－Ｍｇ, Ｎｉ－Ｍｇ 主元素及有关比值和端员组分之间的关系, 分析研究了不同岩类包体中尖晶石的颜色、成分及成因之间的联系。并利用所分析的有关橄榄石、斜方辉石、单斜辉石共生矿物的电子探针分析数据, 采用新的、较合理的Ｂｒｅｙ－Ｋｏｈｌｅｒ温度计及Ｋｏｈｌｅｒ－Ｂｒｅｙ 压力计和Ｂａｌｌｈａｕｓ ｅｔａｌ． 氧逸度计算方法进行了计算, 探讨了尖晶石成分与其形成温度、压力和氧逸度状态的关系, 指出了尖晶石成分所反映的地幔亏损程度及部分熔融程度的变化规律及尖晶石 （相） 稳定的温度、压力和氧逸度范围。 相似文献
7.
出露于加拿大苏必利尔罗灵河杂岩体中的含角闪石斑晶和单斜辉石斑晶的煌斑岩，具有碱性，含霞石标准矿物的玄武岩质成分（ＳｉＯ２＜５０ｗｔ％），成分变化从原始岩浆到分异岩浆［Ｍｇ／Ｍｇ＋∑Ｆｅ）＝０．６６－０．４０；Ｎｉ＝２００－３５ｐｐｍ］，岩石富含ＬＲＥＥ［Ｃｅ／Ｙｂ）ｍ＝１６－２６，Ｃｅｎ＝６０－３００；ｎ＝球粒陨石标准化］，Ｓｒ（８７０－１８００ｐｐｍ），Ｐ２Ｏ５（０．４－１．３ｗｔ％）和Ｂａ（１ 相似文献
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在对辽宁省宽甸县花园沟硼矿床的研究中，发现了硼铝镁石，它与遂安石、袁复礼石、硬石膏等并生，产于硼矿体中．硼铝镁石是一种比较稀少的硼酸盐矿物，为此，对其进行了矿物特征的研究．硼铝镁石为黄色，粒状；晶体形态呈短柱状和权状，类似于橄榄石的晶体形态，弱多色性、Ｎｇ－淡黄、Ｎｐ－近于无色；折射率Ｎｇ＝１．７０７６，Ｎｐ＝１．６７０８，Ｎｍ＝１．６９６２；－２Ｖ＝５４°，Ｈ＝６－７，ＶＨＮ１００＝１２１５ｋｇ／ｍｍ２；Ｄ测＝３．５０．化学成分除Ａｌ和Ｍｇ外，其次是Ｆｅ２＋和Ｆｅ３＋，且Ｆｅ２＋＞Ｆｅ３＋晶体化学式为：晶体结构属斜方晶系，空间群ｐｎｍａ，ａ＝９．８９３（６）Ａ，ｂ＝５．０７６（４）Ａ，ｃ＝４．３３５（３）Ａ，Ｚ＝４．成因分析表明，硼铝镁石富Ａｌ、Ｍｇ、Ｂ，经角闪岩相区域变质作用形成． 相似文献
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11.
铬尖晶石成分与晶胞、比重的关系1955年米赫耶夫提出尖晶石类总的晶胞公式为: (单位kx) 两价平均离子半径 三价平均离子半径。 相似文献
12.
The Guleman ophiolite,one of the most important ophiolitic massifs of the Southeast Anatolian Ophiolitic Belt,consists of a core of serpentinized mantle rocks overlain by an ultramafic sequence,layered and isotropic gabbro,and sheeted dykes.The ophiolite structurally overlies the Lower Miocene Lice Formation and is overlain by young sandstones and shales of the Upper Maashtrichtian-Lower Eocene Hazar Complex and Middle Eocene Maden Complex.The Guleman ophiolite tectonically overlain by Precambrian to Upper Triassic Bitlis metamorphic massif.The mantle peridotites compose mainly of fresh and in place serpentinized harzburgite tectonite with local bands and lenses of dunites with large-sized chromitite pods.The Guleman peridotites commonly show porphyroclastic texture,high-temperature fabrics such as kink-bands in olivines.According to microprobe analyses,the harzburgite and dunite have low Ca O and Al2O3 abundance similar to Mariana forearc,and their average Cr-(=Cr/(Cr+Al)atomic)ratio of Cr-spinelsis surprisingly high(0.63)besides Fo content of olivine is between 90.9 to 92.3 in peridotites.According to Mg#(Mg/(Mg+Fe2+))versus Cr#in spinel diagram,the degree of partial melting is higher than 35%and spinel values plot in the forearc peridotites field.The Gulemanharzburgites have low Ca O,Al2O3 and Ti O2 contents in orthopyroxene and clinopyroxene lammelles,resembling those of depleted harzburgites from modern forearcs and different from moderately depleted abyssal peridotites.Consequently,we propose that the Guleman peridotites form in a forearc setting during the subduction initiation that developed as a result of northward subduction of the southern branch of the Neo-Tethys in response to the convergence between Arabian and Anatolian plates. 相似文献
13.
Karen L. Kimball 《Contributions to Mineralogy and Petrology》1990,105(3):337-346
Chromite spinels in hydrothermally altered rocks from fracture-zone ultramafic rocks and from both ultramafic cumulate pods and sheeted dikes in the Josephine ophiolite, California, display a wide variety of compositions. Alteration of the spinel may not be visible in thin section. The primary composition changes accompanying hydrothermal alteration are increase in Cr/(Cr+Al) and/or Fe2+/(Fe2++Mg). In general, altered spinel grains associated with hornblende and chlorite show an increase in Cr/(Cr+Al) from core to rim. Altered spinel grains associated with serpentine show an increase in Fe2+/(Fe2++Mg) from core to rim but may not show an increase in Cr/(Cr+Al). The compositional zoning in some altered spinel grains appears to result both from reaction of clinopyroxene plus spinel to form hornblende, and from reaction of hornblende to form chlorite. These observations suggest that subsolidus hydrothermal metamorphic effects need to be considered when interpreting spinel compositions and the compositions should not be interpreted solely in terms of igneous processes. Further, the presence of highly altered spinels may be indicative of hydrothermal alteration in rocks where other evidence of such alteration is absent. 相似文献
14.
尝试用稀土分布的分形结构因子（FSF）值对我国碱性花岗岩的稀土组成进行了分类。可将我国碱性花岗岩的稀土分布分形结构因子划分为4种类型：（1）弱变异型（0．98－0．95）；（2）中变异型（0．95－0．92）；（3）强变异型（0．92－0．89）；（4）超强变异型（0．89－0．86）。其中前两种类型可很好地对应重稀土富集型和中稀土亏损型花岗岩，而后两种类型可对应轻稀土相对富集型和轻稀土特富型花岗岩。利用FSF值对新疆东准噶尔地区三带富碱花岗岩按稀土组成进行了归类。 相似文献
15.
橄榄岩中尖晶石化学成分分带的机理及其地质意义 总被引：1，自引：1，他引：1
橄榄岩中尖晶石的化学成分分带显示，在由温度降低引起的亚固相平衡过程中，与橄榄石及斜方辉石相邻的尖晶石边缘贫Mg和Al、富Fe和Cr，而与单斜辉石相邻的尖晶石边线相反。尖晶石的Fe和Mg分带为其他矿物的粒间Fe－Mg离子扩散所致；尖晶石中的Cr和Al分带则是尖晶石晶体内部Cr－Al离子的交互扩散所致。本文从热力学理论角度说明了尖晶石晶体内部的Cr－Al交互扩散受其Fe－Mg分带的控制；从热力学计算证明了尖晶石内Al必须从富Fe处向富Mg处扩散，解释了尖晶石中Mg和Al及Fe和Cr分带的一致性。 相似文献
16.
Alteration Mechanisms of Chromian-Spinel during Serpentinization at Wadi Sifein Area, Eastern Desert, Egypt 总被引：1，自引：0，他引：1
Wadi Sifein podiform chromite deposits, Central Eastern Desert of Egypt, are hosted by fully serpentinized peridotite that is a part of the dismembered Pan‐African ophiolite complexes. Relics of primary minerals and the chemical characters indicate that the ophiolitic rocks were derived from depleted mantle peridotite of harzburgite and subordinate dunite compositions. The mantle rocks were initially formed at a mid‐oceanic ridge and subsequently thrust at a supra‐subduction zone. The chromite mineralization at Wadi Sifein area displays either pod‐shaped bodies with massive and lumpy chromitite appearance or dissemination of chromian‐spinel in serpentinite matrix. The podiform chromitite exhibits a very limited compositional range in terms of Cr# [Cr/(Cr + Al) atomic ratio] and Mg# [Mg/(Mg + Fe) atomic ratio]. The chromian‐spinel, however, frequently displays optical and geochemical zoning. Four zones can be identified from core to edge: inner core representing the original composition of the chromian‐spinel; narrow Cr‐rich ferritchromit zone; wide ferritchromit zone; and outer Cr‐magnetite/magnetite zone. The zonation of chromian‐spinel is interpreted to be a result of serpentinization rather than magmatic or metamorphic processes. The geochemical data obtained from the chromitite and chromian‐spinel was statistically processed using discriminant and R‐mode factor analyses. Two trends, minor and major, were achieved considering the formation of ferritchromit. The minor trend is controlled by the redistribution of trivalent cations, where Cr2O3 increased on the expense mainly of Al2O3 and to less extent Fe2O3 to form zone II during the peak of serpentinization. The major trend of alteration, however, is explained by the exchange between Mg‐Fe2+ rather than Cr, Al, and Fe3+ to form zone III. Kammererite formation was accompanied the formation of zones III and IV at a 314°C temperature of formation. 相似文献
17.
Several types of both magmatic and metamorphic spinels have been found in Archean komatiites of the Sovdozero and Kostomuksha greenstone belts in the eastern part of the Fennoscandian Shield. Scanning electron microscopy and Raman spectroscopy revealed relics of cores of primary magmatic chrome-spinels with high Cr and Al contents. In the Sovdozero structure, the relics are better retained than those in the Kostomuksha structure, which is caused by a different degree of metamorphic transformation. The comparable 100 · Cr/(Al + Cr) values of spinel cores from Sovdozero and Kostomuksha reflect similar conditions of partitional melting in the mantle. These data agree with the fact that both komatiite complexes belong to the Al-undepleted petrogenic type. Wide variations in the Cr and Al contents in primary chrome-spinel cores together with a constant Mg/(Fe2+ + Mg) ratio correspond to low oxygen fugacity during magma crystallization. In general, the composition of these primary chrome-spinels is similar to that of accessory phases in peridotites from suprasubduction zones and agrees with hypothesis of komatiite complex formation in back-arc basins. 相似文献
18.
Composition of chromiferous spinel included in olivines of Mg-rich basalts and gabbros of the Deccan Traps (Gujarat and Western Ghats) are reported here. They vary from Al-rich compositions [Al2O3 = 53wt.%; Cr#, 100Cr/(Cr + Al) = 12] to Cr-rich compositions [Cr2O3 = 51wt.%; Cr# = 84], and from Cr-Al rich compositions towards Cr-rich Ti-magnetite (TiO2 up to 23 wt.%, ulvöspinel up to 67mol.%). The Mg# [100Mg/(Mg + Fe2+)] of spinel decreases from 81 to nearly zero. The highest Cr# has been found in the Bushe Fm., Thakurvadi Fm., and some high-Ti basalts of the Pavagadh section, whereas some of the low-Ti basalts of Saurashtra have Al-rich compositions typical of spinels found in mid-ocean ridge basalts. The chemical composition of the Deccan Trap spinels is completely different compared to that observed in mantle spinel suites, with very few exceptions. The decreasing Al and increasing Fe and Ti of spinel seems to be mainly the result of decrease of Mg in the locally coexisting melts and favourable cationic substitutions in the lattice. There is barely any evidence of general relationships between the composition of the Deccan spinels and inferred mantle sources of the host magmas. Pyroxene inclusions in spinels may witness a high-pressure stage of crystallization, but the possibility of non-equilibrium crystallization, or even magma mixing, cannot be ruled out. Overall, the compositional ranges of chromiferous spinel in the Deccan Traps closely match those observed in the other Large Igneous Provinces having mafic/ultramafic intrusions and mafic magma compositions (e.g., Siberian Traps, Karoo, Emeishan). 相似文献
19.
PP3超镁铁岩主要岩石类型有纯橄岩和石榴石橄榄岩,两者为渐变,主要矿物为橄榄石、铬尖晶石、石榴石、单斜辉石和斜方辉石.铬尖晶石的Cr#[Cr/(Cr+Mg) ×100]从51~89变化,TiO2和MnO2值分别低于0.26%和0.46%.铬尖晶石矿物表现为4期次演化的特点,反映了从岩浆期、榴辉岩相、角闪岩相和绿片岩相演化特征.随着超镁铁岩的演化,铬尖晶石表现为Cr#不断增大,而Mg#[Mg×100/(Mg+Fe2+) ]不断减少、氧逸度不断增加的过程.PP3铬尖晶石反映了地幔来源,为大陆岩石圈超镁铁岩特征,后期随折返而演化.从石榴石与铬尖晶石相互转变过程看出,PP3超镁铁岩经历了深度加大的过程,超镁铁岩曾经到达100km以上的岩石圈地幔深处.在绿片岩相-绿片角闪岩相变质过程中,铬尖晶石中Cr、Mg和Al减少,Fe相对增加,产生富Cr尖晶石变质作用样式.晚期剪切变形等次生变化影响了铬尖晶石矿物成分. 相似文献