甘肃西秦岭区新生代碱性火山岩中的钛金云母

本文对甘肃西秦岭区新生代火山岩及所携带的上地幔包体中钛金云母进行矿物学和矿物化学研究。本区火山岩中的金云母与金伯利岩、钾镁煌斑岩和一般云煌岩中的金云母不同，其化学成分显示了一种过渡类型特征。巨晶和粗晶金云母是在＞１３００℃，３０×１０￣８ｐａ，富ＣＯ＿２和Ｈ＿２Ｏ的条件下的早期结晶相。微晶金云母为近液相线快速冷却的产物。橄榄岩包体和球状体中金云母的成因似与流体交代作用有关，这种钛金云母的出现进一步证明新生代火山岩起源于被交代了的地幔，交代流体具有富Ｋ、Ｎａ、Ｔｉ等不相容元素和挥发分ＣＯ＿２、Ｈ＿２的特征。     

青藏高原新生代火山岩矿物化学及其岩石学意义--以玉门、可可西里及芒康岩区为例

本文系统地讨论了青藏高原玉门、可可西里及芒康岩区新生代火山岩中橄榄石、辉石、长石以及石榴子石巨晶和透长石巨晶的矿物化学持征,并利用矿物学资料探讨了火山岩形成的温度及压力条件．指出青藏高原新生代火山岩主体乃是一套陆内造山带钾玄岩系列火山岩,其矿物化学、主元素及同位素特征表明,这套火山岩应起源于加厚陆亮底部的特殊的富集型壳幔混合带。     

冀东马兰峪地区花岗闪长岩中巨晶锆石成因分析

巨晶锆石由于稳定性强，能够很好地保存其形成时的标型和化学特征而成为最重要的矿物地球化学探针之一。本文在通过对冀东马兰峪腰岭子花岗闪长岩中锆石矿物进行阴极射线致发光（CL）图像分析、晶体形态学统计学分析的基础上，结合等离子质谱（LA-ICP-MS）测试工作，解析了马兰峪金矿花岗闪长岩中巨晶锆石的微量元素组成特征，并依据Pupin等（1980）提出的锆石类型分类的主型和亚型及其地质温度表，研究结果表明：巨晶锆石的形成温度650~850℃，巨晶锆石的LA-ICP-MS分析显示Ce正异常和不明显Eu的负异常，并且富集重稀土元素；巨晶锆石可能与区内峪耳崖式金矿存在成因联系。     

蒙阴金伯利岩中金云母的微组构特征及对岩浆演化的暗示

为探讨山东蒙阴金伯利岩的成因及其岩浆演化过程,采用SEM、EPMA和LA-ICP-MS对该区金伯利岩中金云母的微组构进行了分析研究。结果表明,该区岩浆成因金云母主要呈斑晶、显微斑晶和基质云母产出。根据主量元素(Al、Fe和Mg~#)特征将金云母分为原生金伯利岩金云母组、金云母-钡镁脆云母组、金云母-四配位铁金云母组和金云母-黑云母共生组。早期金云母结晶后,在岩浆上升过程中受源条件或矿物相在熔体中再吸收的影响,向II型基质云母、四配位铁金云母、钡镁脆云母演化。晚期通过岩浆改造或与围岩的交代变质作用形成金云母-黑云母巨晶共生组。综上认为,蒙阴金伯利岩岩浆成分受到了多种改造,其演化过程是相当复杂的。     

昌乐地区新生代碱性玄武岩中刚玉、尖晶石巨晶岩相学、矿物化学特征

山东昌乐蕴含中国最大的宝石级刚玉—蓝宝石矿床。昌乐刚玉巨晶与玄武岩界限截然,边缘圆化,沿巨晶溶蚀圆化的边缘发育富铝的尖晶石和钛磁铁矿反应环边,显示其为深源捕虏晶的岩相学特征。对刚玉等巨晶及其反应边矿物进行岩相学、电子探针和LA-ICP-MS(Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry)分析能有效揭示其成因及演化历程。昌乐刚玉2组样品(CL-1和CL-2)矿物化学和关键元素特征及Ga/Mg、Cr/Ga、Fe/Ti、Fe/Mg等关键元素比值显示为岩浆型来源,而CL-2组样品明显叠加了后期熔体交代作用的特征。反应边尖晶石具刚玉巨晶向尖晶石巨晶过渡的成分特征,关键元素特征指示两者具强烈亲缘性,尖晶石巨晶是刚玉经历复杂交代作用的产物。昌乐刚玉呈现碱性熔体中结晶的化学成分特征,极有可能源于交代富集的地幔岩低度熔融形成的富铝的碱性熔体。     

黑龙江镜泊湖地区全新世玄武岩的地球化学特征及其深部过程探讨

镜泊湖地区全新世玄武岩分布在镜泊湖西北方向的“火山口森林”地区和蛤蟆塘地区。这两个地区相距只有１５ｋｍ,但其玄武质岩石在岩石学上具有明显的区别,前者为碱性橄榄玄武岩,后者为白榴石碱玄岩,并且具有钛角闪石、金云母和歪长石巨晶,而前者则没有这些巨晶。对它们的地球化学特征研究表明,两个地区的玄武夺石虽然均属于偏钠质的碱性玄武岩,但是白榴石碱玄岩相对于碱性橄榄玄武岩总体上具有高的Ａｌ２Ｏ３、Ｎａ２Ｏ、Ｋ２     

英安岩中高压辉石巨晶的发现及其意义

在吉林省九台市官马山晚侏罗世英安岩中发现了辉石巨晶。研究表明。该巨晶不是英安岩浆的结晶产物，英安岩的岩相关及地球化学特征显示，它是酸性流纹岩浆与基性偏碱性的玄武岩浆经混合作用形成的，辉石巨晶是后一种岩浆在高压条件下结晶的产物，对辉石巨晶的温压计算结果表明，该矿物结晶温度为１２７６℃，压力为１．２７ＧＰａ。这一深度可相当于该区软流层的顶界。可以认为，晚侏罗－早白垩世火山岩形成于地壳较厚的环境。     

新疆可可托海稀有金属矿床矿物和岩石热红外光谱特征

当前新型材料、新能源在各个领域应用不断深化,稀有金属矿床迎来了世界范围内的研究与勘探热潮。新疆可可托海稀有金属矿床是我国最早开发利用稀有金属矿产资源的重要基地,但对其典型矿物和围岩的热红外反射光谱的认识还很缺乏,制约了对同类型矿床开展遥感地质调查和遥感地质学研究工作的推进。本文采用便携式热红外光谱仪,对可可托海3号脉的典型矿物岩石开展热红外光谱特征研究。结果表明:热红外光谱可以有效识别锂辉石、锂云母、绿柱石、电气石等典型的稀有金属矿物。其中,与锂云母相比,含锂云母伟晶岩产生了新的特征峰;含锂辉石伟晶岩、含电气石伟晶岩相比于各自单晶矿物,其反射特征峰均明显向短波方向偏移;含绿柱石伟晶岩光谱曲线反射特征峰比绿柱石单晶反射特征峰明显向长波方向偏移。本文初步建立了可可托海典型矿物和岩石热红外光谱特征数据库,总结了以锂辉石、锂云母等稀有金属矿床矿物、含矿伟晶岩及围岩的热红外光谱特征,可为热红外光谱进行稀有金属矿物的识别及花岗伟晶岩型矿床的勘探提供必要的基础数据支撑。     

中国东部新生代玄武岩中单斜辉石巨晶的主要特征及成因信息

作者通过对我国东部新生代玄武岩中巨晶Cpx的109个样品的化学成分的统计、计算及投影,研究了Cpx巨晶的产状、物性及矿物化学的主要特征,并对其成因信息提出了自己的看法。Cpx巨晶的成分以A1_2O_3、A1~(v1)较高而Ti、Mg'中等为特征。但在“反应边”中,A1_2O_3、Na_2O、A1、A1~(v1)则明显降低。我国巨晶以普通辉石为主,而透辉石、次透辉石及顽透辉石少见。国内不同地区的Cpx巨晶成分也略有不同:华南区巨晶的Wo较高而A1_2O_3较低;华北区Fs、A1_2O_3较高;而东北区En较高而A1_2O_3中等。有关Cpx巨晶的成因信息,作者的观点是:(1)巨晶Cpx是寄主玄武岩浆在上地幔中结晶的产物,而不是地幔解体的捕虏晶。(2)我国巨晶Cpx的结晶温度是1021—1209℃,压力为1.4—3.2GPa,所以,Cpx巨晶的结晶深度为48—104Km。(3)我国东部新生代玄武岩均产于大陆板块内部,以碱性玄武岩成分为主,而拉斑玄武岩较少。     

焦家式金矿中铬铝云母化学成分的标型性

本文系统研究了胶东地区金矿中产出的铬铝云母亚族中３个白云母、１６个绢云母和３２个含Ｃｒ云母种属的化学成分特征。提出了含Ｃｒ云母种属结构层内四面体、八面体及层间离子种类和数量在焦家式金矿成矿过程中的指示作用，阐明了白云母、绢云母及含Ｃｒ云母种属之间的演化特征在与焦家式金矿化有关的成岩成矿作用中的标型意义。     

黑龙江省科洛—二克山富钾火山岩的辉石和长石巨晶

本文对富钾火山岩中单斜辉石、斜方辉石、长石巨晶的物理性质、化学成分、微量元素等特征进行了研究。文中还对巨晶的成因及对岩浆的影响问题,提出了作者自己的观点。     

Discovery of Pyrrhotite-Chalcopyrite-Bearing Amphibole Megacrysts in Tongling Area, Anhui Province

Some pyrrhotite-chalcopyrite-bearing amphibole megacrysts (including pyroxene megacrysts) were discovered in Mesozoic augite diorite-porphyrite at Caoshan in Tongling area, Anhui Province. The amphibole megacrysts, belonging mainly to pargasite and magnesiohastingsite, are characteristic of the amphibole composition derived from mantle and crystallized in lower crust. In general, the aggregates of pyrrhotite-chalcopyrite take the shapes of cylinder and sphere. Three occurrences have been recognized in the amphibole megacrysts: parallel linear, bunchy and scattered. The unique cylinder-like shape of the aggregates and remarkable Ni-poor sulfides in Caoshan are distinctively different from the spherical Ni-rich sulfides in pyroxene megacrysts and any other kinds of megacrysts. In terms of composition, the amphibole megacrysts and their sulfides in Caoshan are similar to those in the pyroxenite xenoliths in Qilin, Guangdong Province. In terms of origin, the pyrrhotite-chalcopyrites as exsolution products resulted from the subsolidus re-equilibration of sulfide solid solution within amphibole megacrysts.amphibole megacrysts were first discovered inside and outside China. This discovery is important for the study of regional magma evolution and its associated mineralizations and ore sources as well.     

REE Abundaces in Megacrysts and Host Basalts：REE Behavior of Magma at High Pressures

Based on REE abundances in megacrysts and host basalts and their equilibrium conditions,it has proved that megacrysts may have been produced from the magma derived from the host rocks or of more basic composition.The REE ratios of megacrysts to host rocks may be taken as partition coefficients when both are equilibrium with each other.The crystal fractionation of megacrysts has caused the evolution of REE in the magma.It is obvious that some host basalts are the product of magma evolution after crystal fractionation.According to REE abundances in the host rocks and the partition coefficients between crystal and liquid,the history of crystal fractionation of magma can be traced.     

Origin of clinopyroxene megacrysts in volcanic rocks from the North China Craton: a comparison study with megacrysts worldwide

ABSTRACT

Clinopyroxene megacrysts in volcanic rocks can provide substantial information on the evolution of the magmatic system at depth. Although considerable attention has been paid to these crystals, their origin is not yet completely resolved. The clinopyroxene megacrysts worldwide can be divided into two major types in general: the green Cr-diopside type and the black Al-augite type. There is a consensus view that the Cr-diopside megacrysts are mantle xenocrysts, whereas two contrasting opinions exist regarding the origin of the black Al-augite megacrysts. One favours a cognate origin, viewing them as crystallization products of the host magmas under high-pressure; while the other argues that they are xenocrysts crystallized from previous alkali basalts or fragments of mantle peridotites, pyroxenites or pegmatite veins. A review study on the clinopyroxene megacrysts in Meso-Cenozoic volcanic rocks from the North China Craton (NCC) and their comparison with those worldwide provides new constraints on their origin, namely, the Cr-diopside megacrysts, as previously thought, are all xenocrysts, representing disaggregated clinopyroxene crystals from clinopyroxene-rich mantle rocks. Contrary to the formerly proposed cognate origin, the Al-augite megacrysts are also xenocrysts, having no direct genetic link to their host rocks. They crystallized from melts that have formed earlier than the host magmas, and probably accumulated in a magma chamber or occurred as sheets or veins filling a fracture network surrounding a magma chamber in the upper mantle. During the subsequent eruption of the host lavas, these previously formed crystals were incorporated into the magma and were brought up to the surface.     

Cr-rich megacrysts of clinopyroxene and garnet from Lac de Gras kimberlites,Slave Craton,Canada – implications for the origin of clinopyroxene and garnet in cratonic lherzolites

Kimberlites from the Diavik and Ekati diamond mines in the Lac de Gras kimberlite field contain abundant large (>1 cm) clinopyroxene (Cr-diopside) and garnet (Cr-pyrope) crystals. We present the first extensive mineral chemical dataset for these megacrysts from Diavik and Ekati and compare their compositions to cratonic peridotites and megacrysts from the Slave and other cratons. The Diavik and Ekati Cr-diopside and Cr-pyrope megacrysts are interpreted to belong to the Cr-rich megacryst suite. Evidence for textural, compositional, and isotopic disequilibrium suggests that they constitute xenocrysts in their host kimberlites. Nevertheless, their formation may be linked to extensive kimberlite magmatism and accompanying mantle metasomatism preceding the eruption of their host kimberlites. It is proposed that the formation of megacrysts may be linked to failed kimberlites. In this scheme, the Cr-rich megacrysts are formed by progressive interaction of percolating melts with the surrounding depleted mantle (originally harzburgite). As these melts percolate outwards, they may contribute to the introduction of clinopyroxene and garnet into the depleted mantle, thereby forming lherzolite. This model hinges on the observation that lherzolitic clinopyroxenes and garnets at Lac de Gras have compositions that are strikingly similar to those of the Cr-rich megacrysts, in terms of major and trace elements, as well as Sr isotopes. As such, the Cr-rich megacrysts may have implications for the origin of clinopyroxene and garnet in cratonic lherzolites worldwide.

     

北京周口店岩体中钾长石巨晶的特征及成因

花岗岩类岩石中的钾长石巨晶,有的认为是斑晶,有的认为是变斑晶。本文通过对北京周口店岩体中钾长石巨晶的野外产状、显微结构、矿物化学等特征研究,证明巨晶是在岩浆结晶作用的早—中期阶段,直接从不饱和水的熔体中生长而成的斑晶。钾长石巨晶多见于较贫钾长石组分的花岗岩类岩石(石英二长岩-花岗闪长岩)中,其原因可能是,与花岗岩和白岗岩岩浆相比,这种成分的岩浆温度较高,粘度较小,组分扩散较快,钾长石的成核速率较小,而生长速度较大。周口店岩体中钾长石巨晶的大小和含量的变异,可能主要受冷凝梯度dT/dt的控制。     

河北汉诺坝玄武岩中深源包体和巨晶分布的动力学机理

汉诺坝碱性玄武岩是深源包体和巨晶的主要寄主岩,同时,也有不含包体的碱性玄武岩和含包体的拉斑玄武岩。本文基于理论计算,探讨了包体和巨晶分布的动力学机理。     

库车坳陷盐下构造对盐上盖层变形的影响因素分析

库车坳陷是在地壳或者岩石圈尺度整体挤压作用下,收缩构造变形形成的一个构造单元,膏盐岩层等软弱岩层可能导致滑脱断层发育,并引起盐上和盐下不协调收缩变形,区域挤压作用下一些先存基底断裂带的逆冲位移是控制盐上层冲断褶皱变形的主要因素。运用地震资料、地表露头、钻测井资料以及非地震资料等,对库车坳陷区域大剖面的盐上层、盐下层的构造变形样式进行分析,认为南天山在挤压收缩变形中隆升,诱导盆山过渡带发育基底卷入的高角度逆冲断层,先前基底断层的复活影响了盆地沉积盖层的构造变形,基底断裂与盖层断层组合样式在走向上基本一致,盖层强变形带与基底断裂带上下呼应。     

How late are K-feldspar megacrysts in granites?

Various petrologists have suggested that K-feldspar megacrysts grow in granites that are extensively crystallized, even at subsolidus conditions. However, experimental evidence indicates that, though K-feldspar nucleates relatively late in the crystallization history, abundant liquid is available for development of large crystals. A great deal of evidence, involving many different factors, favours a magmatic/phenocrystic origin for K-feldspar megacrysts in granites, namely simple twinning, oscillatory zoning, euhedral plagioclase inclusions, and concentric, crystallographically controlled arrangements of inclusions. In addition, abundant evidence has been presented of (1) mechanical accumulation of K-feldspar megacrysts in granites, (2) alignment of megacrysts and megacryst concentrations in magmatic flow foliations, (3) involvement of megacrysts in zones of magma mixing in granite plutons, and (4) occurrence of megacrysts in some volcanic rocks, implying that the megacrysts were suspended in enough liquid to be moved without fracturing or plastic deformation. Detailed trace element and isotopic data also indicate that megacrysts can move between coexisting felsic and more mafic magmas. Irregular overgrowths on megacrysts are consistent with continued magmatic growth after euhedral megacrystic growth ceased, the overgrowths being impeded by simultaneously crystallizing quartz and feldspar grains.     

Amphibole-rich xenoliths and host alkali basalts: petrogenetic constraints and implications on the recent evolution of the upper mantle beneath Ahaggar (Central Sahara,Southern Algeria)

Quaternary basanitic to nephelinitic volcanoes from Tahalra (western Ahaggar, southern Algeria) contain numerous Mg-ilmenite and amphibole-rich inclusions (±olivine, ±salite) and spinel lherzolite (±pargasite) inclusions associated with kaersutite megacrysts. On the basis of petrological, geochemical and Sr isotopic study of representative xenoliths (including a composite nodule defined as a vein cross-cutting peridotite) and lavas, we attribute the series of amphibole-rich xenoliths and megacrysts to segregation under upper mantle conditions from a hydrous high Ti and LREE melt geochemically similar to the Quaternary basanite but isotopically different. Amphibole-rich rocks and megacrysts are the results of magmatic events (less than 40 Ma) probably contemporaneous with the various pre-Quaternary volcanic phases recognized in Ahaggar. The amphibole-rich veins and the Quaternary lavas have a garnet lherzolitic source enriched in REE (7 to 9 times chondritic in LREE, 2 times in HREE). This enrichment probably results from former metasomatic events unrelated to the recent magmatic history. Melts from which these veins precipitated within upper mantle peridotite also account for mantle enrichment processes; they induced a local partial melting and contact metasomatism (pargasitization). The upper mantle beneath the volcanic areas of Ahaggar is veined and hydrous, and consequently lightened: thus, the uplift of basement may be the isostatic response to magmatism and related metasomatism and therefore the result of the Cenozoïc igneous activity.