苏北盆地新生代玄武岩中的地幔橄榄岩包体

苏北盆地盘石山和方山新生代玄武岩中广泛发育橄榄岩包体,以尖晶石二辉橄榄岩为主,少数为尖晶石方辉橄榄岩。盘石山橄榄岩的岩相学特征表明其经历过Ol Cpx Melt=Ol Opx Melt的反应过程,而方山橄榄岩的这种反应过程不明显,表明古老的岩石圈地幔物质在方山下部仍有残留。与华北地块东部早古生代地幔橄榄岩相比较,本地区橄榄岩包体中橄榄石的Fo值为0.89～0.90,斜方辉石的En值为0.88～0.90,表现为饱满玄武质组分的特点,表明从早古生代至新生代期间经历了岩石圈的减薄和岩石圈地幔的置换。平衡温压估算结果表明,方山橄榄岩平衡温度为985℃～1 081℃,平衡压力为1.65 GPa～2.61 GPa,对应的深度为53 km～84 km;盘石山橄榄岩平衡温度为940℃～1 010℃,平衡压力为0.90 GPa～2.07 GPa,对应的深度为29 km～66 km。盘石山橄榄岩包体的起源深度小于方山,苏北盆地新生代时期岩石圈地幔的厚度约为50 km,位于岩石圈30 km～80 km之间。     

Clinopyroxene-melt Equilibrium of Cenozoic Basalts in Kuandian, Hannuoba and Mingxi areas, Eastern China and Its Importance

1. Introduction The depth of source of Cenozoic basalts and the genesis of mantle xenoliths in eastern China have been widely discussed by many geoscientists. There were basically two main opinions: one was that the relationship of basalts and the peridotite xenoliths are melt and residues (Cong et al, 1982; Liu et al, 1985; Qiu et al, 1986; E et al, 1987; Chi et al, 1988; Deng et al, 1988), and pyroxenite and gabrro enclaves are accumulation of fractional crystallization (Qiu et al, 1986;…     

云南马关地区碧玄岩中单辉橄榄岩包体的成因

云南马关地区分布有许多碧玄岩岩管，其中有些岩管含有地幔橄榄岩包体、笔者在该区工作时着重对含角闪石单辉橄榄岩包体进行了研究，并从地球化学和热力学角度探讨了此类包体的成因机制。     

华北地台部分麻粒岩地体及包体的地球化学特征对比

华北地台麻粒岩包体（汉诺坝）与麻粒岩地体（西望山、蔓菁沟）存在明显的岩石地球化学特征差异，麻粒岩包体总体成分偏基性，麻粒岩地体总体成分偏长英质。形成时间、空间及构造背景的不同是造成成分差异的重要因素。汉诺坝麻粒岩包体是在拉线环境下玄武质岩浆底侵下地壳后结晶分异过程中堆晶作用的结果，其主、微量元素成分受控于辉石和斜长石堆晶的相对比例；下地壳物质的混染作用不是造成麻粒岩包体Nb、Ta、Th、U亏损的惟一因素，底侵的玄武质岩浆可能发生了含钛矿物相的结晶分离，造成了汉诺坝麻粒岩包体Nb、Ta亏损，而下地壳的麻粒岩相变质作用则使Th、U发生亏损。麻粒岩地体存在两种不同性质的微量元素组成，反映了两种不同构造环境的并置，是构造挤压抬升的结晶。     

山东栖霞大方山玄武岩中地幔熔体玻璃捕虏体岩相学及岩石化学研究

过去地学界对固体地幔岩捕虏体研究已经相当充分。另外,山东栖霞大方山还存在地幔熔体玻璃捕虏体,其化学成分、矿物成分既不同于固体地幔岩也不同于寄主玄武岩。此玻璃体特别富K,而且早于寄主岩浆,二者间很不平衡。富K玻璃捕虏体往往被玄武岩浆消化殆尽,但在野外仍然可以找到少量残留体供室内研究。此熔体玻璃的存在意味着该区玄武岩浆作用不是一元而是多元岩浆体系,还存在早一期的碱性地幔岩浆。后者消化混染于玄武岩浆之中,会产生富K玄武岩。     

地幔岩包体中斜方辉石的GOD化现象

对我国东部四个地点碱性玄武岩中地幔岩样品的研究分析表明,地幔岩包体被带上来的过程中,斜方辉石比单斜辉石更易发生部分熔融,而形成熔体玻璃（Ｇｌａｓｓ）、橄榄石（Ｏｌｉｖｉｎｅ）和铬透辉石（ＣｈｒｏｍｅＤｉｐｓｉｄｅ）集合体,此作用可称为ＧＯＤ化。ＧＯＤ化沿包体边部最发育,向内逐渐减弱,以至消失。当玻璃极富Ｋ２Ｏ时,出现强烈ＧＯＤ化。在强烈ＧＯＤ化外面的寄主岩石中,还形成销沸石和／或方沸石聚集体。斜方辉石的ＧＯＤ化不仅是由于升温降压而导致的不一致熔融所致,而且还伴有物质的交换（带入ＣａＯ＋Ｎａ２Ｏ＋Ｋ２Ｏ,带出ＳｉＯ２＋ＭｇＯ）。     

金伯利岩中的云母

我国金伯利岩中的云母主要为金云母。镁黑云母和铁黑云母较少见。根据金伯利岩中云母的光学性质,将其分为正吸收和反吸收云母。一般反吸收云母沿正吸收云母的解理面及边缘进行交代。反吸收金云母在四面体位置中,有相当多的Fe~(3+)。环带状云母的成分,从中心向边部不规则变化。富含金刚石的金伯利岩的基质云母含FeO,TiO_2低。云母加热至1100℃时,则变化为橄榄石和石榴石。     

Origin of micro-layering in a deep magma chamber: Evidence from two ultramafic–mafic layered xenoliths from Puy Beaunit (French Massif Central)

The origin of magmatic layering is still hotly debated. To try to shed some light on this problem, two ultramafic–mafic layered xenoliths from Puy Beaunit (French Massif Central) were investigated in detail. The nodules belong to a stratiform intrusion emplaced in the deep crust during the Permian (257 ± 6 Ma; Féménias, O., Coussaert, N., Bingen, B., Whitehouse, M., Mercier, J.-C., Demaiffe, D., 2003. A Permian underplating event in late- to post-orogenic tectonic setting. Evidence from the mafic–ultramafic layered xenoliths from Beaunit (French Massif Central). Chem. Geol. 199 293–315.). The 3 to 5 cm thick nodules have, in common, a central orthopyroxenite layer; the succession of layers is, respectively, norite–orthopyroxenite–norite (PBN 00-01) and norite–orthopyroxenite–harzburgite (PBN 00-03). The variations of both major (by electron microprobe) and trace, essentially the RE, elements (by LA-ICP-MS) were measured in major mineral phases (orthopyroxene, clinopyroxene, plagioclase, spinel) along cross-section perpendicular to the layering. Strong grain size, chemical and textural variations occur along these sections: they can be continuous or discontinuous, symmetrical or asymmetrical. Such complex variations cannot be solely related to a single magmatic history (fractional crystallisation, mineral sorting). Other processes such as element enrichment by residual liquid channelling along layer boundaries and/or sub-solidus recrystallisation and element redistribution must be invoked. It appears, in particular, that element distribution in the central orthopyroxenite layer could result from the injection of micro-sills of orthopyroxene-rich liquid between previously consolidated layers.     

冀北张家口地区汉诺坝玄武岩中麻粒岩捕虏体的硫化物相

捕虏体麻粒岩是了解下地壳形成和演化的重要样品。汉诺坝新生代玄武岩中的二辉麻粒岩捕虏体样品中富含各种硫化物相,主要类型有:①孤立产出的球状出溶硫化物;②矿物颗粒之间或颗粒内的粗晶硫化物;③次生硫化物包裹体群;④裂隙充填硫化物。电子探针分析表明,硫化物的矿物成分均为贫镍磁黄铁矿,(Ni+Co+Cu)/Fe(原子比)远小于0.2;(Fe+Cu+Co+Ni)/S(原子比)比地幔岩的磁黄铁矿小,多小于0.875,反映了一种S过饱和环境。各种产状的磁黄铁矿中Au、Ag都有一定的含量,其平均值分别为0.19%～0.22%(Au)、0.01%～0.02%(Ag),反映下地壳的麻粒岩化与金矿化的成因联系。磁黄铁矿的Ni、Co、Cu含量与S正相关,说明微量重金属元素与S具有同源的关系,由于地幔去气伴随S而进入下地壳。     

Survival of eclogite xenolith in a Cretaceous granite intruding the Central Dabieshan migmatite gneiss dome (Eastern China) and its tectonic implications

Investigation of an eclogite xenolith, discovered in a Cretaceous granite from the Central Domain of the Dabieshan massif in eastern China, yields new petrological insights into the high to ultrahigh-pressure metamorphism, experienced by the Qinling-Dabie orogen. Prior to inclusion as a xenolith in the granite during the Early Cretaceous, this eclogite xenolith had recorded a complex metamorphic evolution that complies with subduction and exhumation processes experienced by the continental crust of the South China Block. Well-preserved mineral parageneses substantiate the prograde and retrograde stages revealed by inclusions in porphyroblastic garnet and zoned minerals such as garnet, omphacite and amphibole in the matrix. The relatively low P/T re-equilibration during a late metamorphic stage was textually inferred by the presence of aluminous and calcic-subcalcic amphiboles such as katophorite, edenite, taramite and pargasite as main matrix phases. According to our U/Pb, Rb/Sr and new ⁴⁰Ar/³⁹Ar geochronological results, namely109 ± 1 and 112 ± 2 Ma plateau ages for muscovite and amphiboles, respectively, two successive but distinct cooling stages account for the thermal history of the granite–migmatite gneiss dome that forms the Central Dabieshan Domain. We argue that prior to the Cretaceous doming, the Central Dabieshan Domain experienced a tectono-metamorphic evolution similar to that observed in the high-pressure to ultra high-pressure units developed in the Southern Dabieshan Domain and Hong’an massif.