内蒙古集宁新生代玄武岩中橄榄岩包体和巨晶的发现及意义

内蒙古集宁新生代玄武岩产于华北克拉通北缘，属于广义的“汉诺坝玄武岩”。首次在三义堂附近的碱性玄武岩中发现了大量的橄榄岩包体、辉石和长石以及少量的含钛磁铁矿巨晶。包体主要是尖晶石二辉橄榄岩，造岩矿物为橄榄石＋斜方辉石＋单斜辉石＋尖晶石，辉石巨晶主要为透辉石和普通辉石，长石巨晶主要是歪长石和少量斜长石。1．5GPa条件下，尖晶石二辉橄榄岩样品所记录的平衡温度与汉诺坝相近，集中于950℃左右，大体上反映了华北克拉通北缘大陆岩石圈地幔尖晶石相部分的温度状态。单斜辉石巨晶的结晶温压大于幔源包体的平衡温压，表明巨晶的来源深度可能大于包体。包体的结构及矿物成分分析表明，这些包体是玄武质岩浆上升过程中偶然捕获岩石圈地幔的岩石碎块。二辉橄榄岩包体中橄榄石高Mg#值（89．5～91．7）和较高的NiO含量（0．29％～0．55％），暗示集宁玄武岩中的橄榄岩包体来自较高熔融程度的岩石圈地幔。     

河北阳原新生代玄武岩中两类辉石岩包体的矿物学和地球化学特征

位于大兴安岭-太行山重力梯度带西侧的阳原新生代玄武岩中含有大量橄榄岩和辉石岩包体。辉石岩包体含有绿色的Cr辉石岩和黑色的Al辉石岩包体两种类型,均为二辉岩,且多数样品中单斜辉石含量高于斜方辉石。岩石结构和主微量元素组成说明阳原辉石岩是高压堆晶体。其EMI型Sr-Nd同位素特征,明显不同于寄主玄武岩,暗示两者没有成因联系,而可能代表古老岩浆事件的产物。综合文献资料发现重力梯度带西侧的辉石岩包体大多具有富集同位素特征,而东侧的样品以亏损同位素组成为主。这种空间上的成分差异暗示重力梯度带分隔两个不同的地幔域,也可能与重力梯度带两侧岩石圈地幔形成时代不同有关。     

广东汕头梅花农场煌斑岩脉中的微型辉长岩质包体

在中国东南部,以往报道获得的深部样品是玄武质岩石中的捕虏体,而笔者发现的是在广东汕头梅花农场附近煌斑岩脉中的辉长岩质包体。该处距离已发现辉长岩质麻粒岩、橄榄岩、辉石岩等包体的广东普宁麒鳞玄武质角砾岩筒仅28公里。辉长岩包体由斜长石、单斜辉石组成,一般大小在0.2~0.6cm左右,虽然产在煌斑岩中,但包体显示辉长结构,自形—半自形的辉石和斜长石紧密接触交生,具有原生近于等粒的粒状结构。包体发育多种变形构造,如双晶纹弯曲或被错断、折断,应力绢云母化等,并可见糜棱岩化现象。汕头梅花农场辉长岩质包体的特征与非洲大裂谷亚的斯亚贝巴南部Akaki-Duncon地区一个火山链玄武岩中的辉长岩俘虏体类似。     

韭菜地等地的新生代玄武岩及其超镁铁岩包体的岩石学研究

韭菜地和鸡笼山两地的玄武岩为新生代的火山锥体,主要岩石为碧玄岩和碱性橄榄玄武岩,其中含有较丰富的超镁铁岩包体。玄武质岩石属碱性系列的钾质亚系,SiO_2不饱和,Al_2O_3较低且富含K、Ti和P等不相容元素,具有Al_2O_3/CaO值较高、M值在60—70之间、固结指数近于40、熔融程度低(4％)等特征,表明玄武质岩石是地幔橄榄岩低度熔融的产物。超镁铁岩包体中易熔组分与不饱和型包体组分相近,其矿物化学特征为:橄榄石的Fo值和斜方辉石的En值较低,单斜辉石的Al_2O_3、TiO_2和Na_2O较高,表明包体相对地富集易熔组分,与原始地幔组分相似。估算包体的矿物平衡温度和压力分别为1050℃和21.6×10~3Pa。     

广丰新生代基性岩多世代辉石矿物学特征及意义

穿插在江西广丰早白垩纪红盆中的碱性基性岩，K—Ar年龄为40．6Ma,基性岩中辉石有基质、斑晶二种类型三个世代，早世代辉石斑晶为巨晶、堆晶，是“Ⅱ型包体”；晚世代辉石斑晶为小斑晶、堆晶；伴生有适量橄榄石斑晶；最晚晶出的是基质中的辉石。多世代辉石的出现为反演该区深部地质特征提供了依据。     

鲁西中生代闪长岩中深源橄榄岩类包体的研究

鲁西中生代侵入岩依次生成辉长岩系列、二辉石闪长岩系列、角闪闪长岩系列、二长岩系列和正长岩系列(林景仟等,1989)。近年来,我们在属于二辉石闪长岩系列的莱芜铁铜沟岩体、矿山岩体和邹平茶叶山岩体中发现了大量不同成因类型的橄榄岩类包体。这些包体为认识鲁西地区中生代岩浆起源、岩石圈结构及上地幔中的超镁铁质岩浆作用提供了重要的信息。 1.包体成因类型及岩石学特征所发现的橄榄岩类包体的主要岩石类型有纯橄岩、方辉橄榄岩、二辉橄榄岩和橄辉岩;以前两类为主,与二辉岩、单辉辉石岩、辉闪岩和角闪岩包体相伴生。根据岩石结构和矿物成分特征,这些包体可划分为亏损型上地幔纯橄榄岩、方辉     

安徽铜陵岩浆岩中辉长质岩石包体的发现及其地质意义

在安徽铜陵白芒山、老庙基和小铜官山岩体中发现了3个辉长质岩石包体。报道了这些辉长质岩石包体及其寄主岩的岩相学观察以及矿物电子探针和全岩岩石化学、微量元素、稀土元素和锶钕同位素分析资料,总结了辉长质岩石包体的特征,讨论了它们的地质意义。该区辉长质岩石包体主要有两类。一类具“斑状”结构,“斑晶”主要是斜长石和角闪石。“基质”具微粒半自形一自形等粒状结构,主要矿物成分为斜长石和角闪石;另有少量黑云母,有时还有少量辉石。另一类具辉长结构,主要由辉石、斜长石、角闪石和黑云母组成。本区辉长质岩石包体低铝高镁和富碱,其Cr,Co和Ni的含量明显偏高,重稀土元素,特别是钇相对富集,(^87Sr／^86Sr)．为0．7063到0．7069,εNd(t)为-4．9～-8．8,与大陆裂谷碱性玄武岩的特征一致,表明本区此时属于拉张环境。研究还表明,铜陵地区不具“斑状”结构的辉长质岩石包体是由底侵的碱性玄武岩浆在约26km深处的深位岩浆房中直接冷凝结晶形成的。本区具“斑状”结构的辉长质岩石包体中的“斑晶”由闪长质岩浆在8～13km深处的中位岩浆房中发生结晶分异作用形成,而“基质”是在“斑晶”形成以后,由深位岩浆房中的中基性演化岩浆上侵到中位岩浆房,并围绕早期“斑晶”矿物结晶而形成。     

江苏盘石山二辉橄榄岩包体的Nd、Sr、Pb同位素特征

对盘石一带的６个二辉橄榄岩包体，３个单斜辉石的Ｎｄ、Ｓｒ同位素，４个全岩、７个单斜辉石和１个斜方辉石的铅同位素进行了测定。结果表明，它们在亏损的岩石圈中经历了长时间的演化，其Ｒｂ－Ｓｒ、Ｓｍ－Ｎｄ、Ｐｂ－Ｐｂ同位素体系的相关性可能反映了不同时期的地幔过程。位于陆下岩石圈地幔中上部位的包体比下部岩石圈地幔具有相对亏损和不均一的同位素特征。     

铜陵中酸性侵入岩同源包体特征及岩浆动力学

铜陵地区中生代中酸性侵入岩的钙碱性系列岩石中,发育同源浅源包体(闪长质微粒包体),而碱性系列岩石中发育同源深源包体(辉石岩和角闪石岩)。它们在矿物化学、稀土微量元素地球化学特征方面与其寄主岩石具有相似性,但在形成的物理化学条件和岩浆动力学特征方面存在一定的差异。反映了它们是同源岩浆在不同岩浆作用阶段的产物,即深源包体来自深位岩浆房中的堆积岩碎块,而浅源包体则来自浅位岩浆房的冷凝边碎块。     

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。     

Mineral chemistry and zoning in eclogite inclusions from Colorado Plateau diatremes

Eclogite inclusions from kimberlitic diatremes on the Colorado Plateau contain intricately zoned garnet and pyroxene and unusual textures. Detailed electron microprobe traverses for a clinopyroxene-garnet-phengite-lawsonite-rutile assemblage show garnet zoning from Alm₆₉Gr₂₁Py₁₀ (core) to Alm₆₁Gr₁₃Py₂₆ (rim) and pyroxene zoning from Jd₅₀ (core) through Jd₇₇ to Jd₅₅ (rim). Pyroxene cores are Cr-rich in another rock. Sharp compositional discontinuities and zoning reversals are preserved in garnet and pyroxene. Oscillatory zoning occurs in both phases on a 10–20 m scale, with variations of up to 6% Py in garnet and 15% Jd in pyroxene. Phengite is unzoned and contains 74% celadonite endmember.Skeletal, pyroxene-filled garnet crystals are common in some rocks, and garnets in other rocks clearly began growth as shell-like crystals. Some rocks contain domains of coarse, prismatic pyroxene with very fine-grained, interstitial magnesium silicates. The texture appears to have resulted from crystallization in the presence of a fluid phase, and water pressure is inferred to have equalled total pressure during crystallization. Eclogite formation at high water pressure may reflect subcrustal crystallization.An analysis of error propagation shows that ferrous iron calculations from electron probe data are not meaningful for these jadeitic pyroxenes, and temperature differences between core and rim crystallization cannot be documented. The garnet textures and oscillatory zoning are unusual for metamorphic rocks, and they suggest disequilibrium crystallization after overstepping of reaction boundaries. All data fit a model of eclogite formation during cooling and metasomatism of basaltic dikes intruded into a cool upper mantle, but the results here do not preclude other origins, such as subduction zone metamorphism.     

Accretionary rims on inclusions in the Allende meteorite

Many inclusions in Allende, particularly those with irregular shapes, are surrounded by a sequence of thin layers which differ from one another in texture, mineralogy and mineral-chemistry. The layer underlying all others contains either: IA, pyroxene needles + olivine + clumps of hedenbergite and andradite; IB, olivine doughnuts; or IC, rectangular olivine crystals. The next layer outward, II, contains tiny (<5 μm) olivine plates and Layer III large (5–10 μm) olivine laths. The final layer, IV, occurs as clumps of andradite + hedenbergite surrounded by magnesium-rich pyroxene needles. It separates Layer III from the Allende matrix which is more poorly sorted and more sulfide-rich than Layer III. Nepheline and iron sulfide are common constituents of most layers, the latter being particularly fine-grained and abundant in Layer II. Although not every layer is present on every inclusion, the sequence of layers is constant. Evidence that the rims are accretionary aggregates includes the presence of highly disequilibrium mineral assemblages and the fact that they are highly porous masses consisting of many euhedral crystals with few intergrowths. In addition, the layers are thickest in topographic hollows on the surfaces of inclusions and the inner layers are absent or discontinuous beyond such irregularities, suggesting that the probability of accretion of crystals was low initially, except in pockets, and became greater later, after a soft cushion of accreted condensate crystals had already formed. Separation of assemblages of different mineralogy, mineral-chemistry and texture into different rim layers seems best explained by nebular models in which long, slow cooling histories allow differentiation during condensation by grain/gas separation processes.     

肇东和亳县陨石中的黑包体及其成因意义

肇东、毫县陨石中的黑包体在总体成分、形状、大小上与陨石球粒相似,但两者的内部结构以及矿物组合不同。黑包体中矿物呈密堆状,主要由细粒橄榄石以及其它硅酸盐微晶组成,不含火成玻璃等特点表明黑包体未经历过熔融,它们可能是形成球粒的毛坯。因此认为球粒的形成有三个阶段:星云凝聚形成尘粒—尘粒吸积形成黑包体—黑包体熔融形成球粒。     

小秦岭东吉口印支期辉石正长岩年代学及其地质意义

东吉口辉石正长岩是小秦岭地区此前唯一获得加里东期年龄的岩体,呈不规则卵圆状侵入于古元古代太华群高级变质岩中,发育弱片麻理。详细的岩相学观察发现,岩体内部可以分为两种具不同结构特征的岩性,从野外接触关系来看:细粒辉石正长岩形成较早,发育烘烤边;中粒含斑辉石正长岩略晚,发育冷凝边。二者的矿物均由斜长石、钾长石、辉石、角闪石、石英等组成,斑晶主要为辉石和斜长石,辉石和角闪石均发生退变质作用。细粒辉石正长岩LA-ICP-MS锆石U-Pb测年结果为(214.8±3.1) Ma（MSWD=0.48）,中粒含斑辉石正长岩为(212.9±3.1) Ma（MSWD=5.6）,均形成于晚三叠世印支期,而不是此前认为的加里东期。这一组年龄表明,小秦岭地区加里东期岩浆活动可能极其微弱,或者不存在该期岩浆活动。总结前人资料,发现东吉口辉石正长岩的形成时代与小秦岭印支期成矿事件同时,印支期岩浆活动与洋陆俯冲转为陆陆碰撞作用有关,强烈的壳幔相互作用导致了深部物质的上涌,岩浆活动为金的富集提供了热驱动力。     

Valence of titanium and vanadium in pyroxene in refractory inclusion interiors and rims

The clinopyroxene in coarse-grained refractory inclusions contains significant amounts of Ti and V, two elements that are multivalent over the range of temperatures and oxygen fugacities under which the inclusions formed. The Ti³⁺/Ti⁴⁺ ratios and the valence of V of these pyroxenes are valuable recorders of nebular conditions. The former can be calculated stoichiometrically from electron probe analyses, but only for relatively Ti-rich grains (i.e., >∼4 wt% ). For Ti-poor pyroxene, and for measurement of V valence, another technique is needed. We have, for the first time, applied K-edge X-ray absorption near edge structure (XANES) spectroscopy to the measurement of Ti and V valence in meteoritic clinopyroxene in refractory inclusions. Use of MicroXANES, a microbeam technique with high (μm-scale) spatial resolution, allowed measurement of Ti and V valence along traverses across (a) Ti-, V-rich “spikes” in pyroxene in Type B1 inclusions; (b) typical grains in a Type B2 inclusion; and (c) the pyroxene layer of the Wark-Lovering rim sequence on the outsides of two inclusions. Measurements of Ti³⁺/(Ti³⁺ + Ti⁴⁺), or Ti³⁺/Ti^tot, by XANES agree with values calculated from electron probe analyses to within ∼0.1, or ∼2σ. The results show that Ti³⁺/Ti^tot increases sharply at the spikes, from 0.46 ± 0.03 to 0.86 ± 0.06, but the V valence, or V²⁺/(V²⁺ + V³⁺), does not change, with V²⁺ ≈ V³⁺. We found that pyroxene in both Types B1 and B2 inclusions has Ti³⁺/Ti^tot and V²⁺/V^tot ratios between 0.4 and 0.7, except for the spikes. These values indicate, to first order, formation at similar, highly reducing oxygen fugacities that are consistent with a solar gas. The pyroxene in the rim on an Allende fluffy Type A coarse-grained refractory inclusion, TS24, has an average Ti³⁺/Ti^tot of 0.51 ± 0.08 and an average V²⁺/V^tot of 0.61 ± 0.06, determined by XANES. These values are within the range of those of pyroxene in the interiors of inclusions, indicating that the rims also formed under highly reducing conditions. Measurements of Ti³⁺/Ti^tot of pyroxene in the rim of a Leoville compact Type A inclusion, 144A, by both XANES and electron probe give a wide range of results. Of our 72 XANES analyses of this rim, 66% have Ti³⁺/Ti^tot of 0.40-0.71, and the remaining analyses range from 0 to 0.38. In data from Simon et al. [Simon J. I., Young E. D., Russell S. S., Tonui E. K., Dyl K. A., and Manning C. E. (2005) A short timescale for changing oxygen fugacity in the solar nebula revealed by high-resolution ²⁶Al-²⁶Mg dating of CAI rims. Earth Planet. Sci. Lett.238, 272-283.] for this sample, 7 electron probe analyses yield calculated Ti³⁺/Ti^tot values that are positive and 15 do not. In the probe analyses that have no calculated Ti³⁺, Ca contents are anticorrelated and Al contents directly correlated with the total cations per 6 oxygens, and the data fall along trends calculated for addition of 1-7% spinel to pyroxene. It appears likely that electron probe analyses of pure pyroxene spots have Ti³⁺/Ti^tot values that are typical of refractory inclusions, in agreement with the majority of the XANES results. The average of the XANES data for 144A, 0.41 ± 0.14, is within error of that for TS24. The rim of 144A probably formed under reducing conditions like those expected for a solar gas, and was later heterogeneously altered, resulting in an uneven distribution of secondary, FeO-, Ti-bearing alteration products in the rim, and accounting for the measurements with low Ti³⁺/Ti^tot values.     

Cumberland Falls chondritic inclusions: Mineralogy/petrology of a forsterite chondrite suite

As previously found for a chondritic inclusion of unknown affinity, mineralogic and petrologic properties of 9 inclusions in the Cumberland Falls enstatitc achondrite are primitive members of the forsterite (F) chondrite group, hitherto defined by 4 meteorites of similar redox state. The inclusions define a primitive suite with properties indicating 8 as F3 and one of even lower petrologic type. The abundant minerals include: low-Ca pyroxene, olivine, plagioclase, kamacite, taenite, schreibersite, troilite, ferroan alabandite and daubreelite. Diopside, oldhamite and a Ti-rich sulfide are present in one or two inclusions. Petrologic textures and jadeitic pyroxene, hitherto unidentified in meteorites, indicate substantial degree of shock. The inclusions acquired their chemical characteristics during nebular condensation and accretion over a broad redox range (metal-silicate trends in them verify Prior's Rules): their parent body later impacted the enstatite meteorite parent body. During impact, the inclusions were shocked and incorporated with enstatite achondrite host as a breccia that would become Cumberland Falls.     

Melt inclusions in olivine from the boninites of New Caledonia: Postentrapment melt modification and estimation of primary magma compositions

Melt inclusions were investigated in olivine phenocrysts from the New Caledonia boninites depleted in CaO and TiO₂ and enriched in SiO₂ and MgO. The rocks are composed of olivine and pyroxene phenocrysts in a glassy groundmass. The olivine phenocrysts contain melt inclusions consisting of glass, a fluid vesicle, and daughter olivine and orthopyroxene crystals. The daughter minerals are completely resorbed in the melt at 1200?C1300°C, whereas the complete dissolution of the fluid phase was not attained in our heating experiments. The compositions of reheated and naturally quenched melt inclusions, as well as groundmass glasses were determined by electron microprobe analysis and secondary ion mass spectrometry. Partly homogenized melts (with gas) contain 12?C16 wt % MgO. The glasses of inclusions and groundmass are significantly different in H₂O content: up to 2 wt % in the glasses of reheated inclusions, up to 4 wt % in naturally quenched inclusions, and 6?C8 wt % in groundmass glasses. A detailed investigation revealed a peculiar zoning in olivine: its Mg/(Mg + Fe) ratio increased in a zone directly adjacent to the glass of inclusions. This effect is probably related to partial water (hydrogen) loss and Fe oxidation after inclusion entrapment. The numerical modeling of such a process showed that the water loss was no higher than a few tenths of percent and could not be responsible for the considerable difference between the compositions of inclusions and groundmass glasses. It is suggested that the latter were enriched in H₂O after the complete solidification of the rock owing to interaction with seawater. Based on the obtained data, the compositions of primary boninite magmas were estimated, and it was supposed that variations in melt composition were related not only to olivine and pyroxene fractionation from a single primary melt but also to different degrees and (or) depths of magma derivation.     

Trace element distribution in mineral separates of the Allende inclusions and their genetic implications

Concentrations of the REE, Sc, Co, Fe, Zn, Ir, Na and Cr were determined by instrumental neutron activation and mass spectrometric isotope dilution analysis for mineral separates of the coarseand fine-grained types (group I and II of Martin and Mason's classification) of the Allende inclusions.These data, combined with data on mineral/liquid partition coefficients, oxygen isotope distributions and diffusion calculations, suggest the following: (1) Minerals in the coarse-grained inclusions (group I) crystallized in a closed system with respect to refractory elements. On the other hand, differences in oxygen isotope distributions among minerals preclude a totally molten stage in the history of the inclusion. Group I inclusions were formed by rapid condensation (either to liquid or solid) in a supercooled solar nebula; extrasolar pyroxene and spinel dust were included but not melted in the condensing inclusions, thus preserving their extrasolar oxygen isotope composition. REE were distributed by diffusion during the subsequent heating at subsolidus temperatures; because oxygen diffuses much more slowly at these temperatures, the oxygen isotope anomalies were preserved. (2) The fine-grained (group II) inclusions were also formed by condensation from a super-cooled nebular gas; however, REE-rich clinopyroxene and spinel were formed early and REE-poor sodalite and nepheline were formed later and mechanically mixed with clinopyroxene and spinel to form the inclusions. The REE patterns of the bulk inclusions and the mineral separates are fractionated, indicating that REE abundances in the gaseous phase were already fractionated at the time of condensation of the minerals. (3) Pre-existing Mg isotope anomalies in the coarse-grained inclusions must have been erased during the heating stage thus resetting the ²⁶Al-²⁶Mg chronometer.     

南极陨石GRV 022115冲击熔融脉矿物学研究

文章主要通过电子探针、扫描电镜、激光拉曼光谱、透射电镜等微区微分析技术研究GRV 022115球粒陨石的基础矿物学特征和冲击变质矿物学特征，探讨陨石冲击熔融脉的形成机制和界定其母体的冲击条件。陨石主岩主要由橄榄石、辉石、熔长石、铁镍金属和硫化物等矿物组成。根据主岩的硅酸盐矿物学特征，确定GRV 022115是风化程度较低（W1） 的L6型普通球粒陨石，与前期分类结果一致。根据熔融脉内含有大量林伍德石的现象，修正GRV 022115陨石的冲击级别为S6，比原定的S5高一个级别。GRV 022115球粒陨石中有多条冲击熔融脉，熔融脉由基质和主岩碎块包裹体两类岩相组组成。熔融脉基质的主要组成是微米级粒状镁铁榴石与纳米级的含铁方镁石，是在平衡冲击压力下结晶的产物。冲击熔融脉主岩碎块包裹体中的橄榄石、低钙辉石、长石碎块已部分或全部转为相对应的高压相。橄榄石相变为林伍德石；个别低钙辉石相变为钙钛矿结构布里奇曼石微晶的集合体；长石主要相变为熔长石与玲根石。几乎所有的主岩碎块都有高温熔融的圆滑边界。熔融脉内外同类矿物的主量和微量元素具有一定的差异性，该差异性可以反映高温高压下混溶作用和扩散作用的影响。结合陨石冲击熔融脉形成机制和结晶模型，根据熔脉基质中镁铁榴石+方镁石矿物组合及静态高温高压实验相图，界定该陨石经受的冲击压力为23~27 GPa。     

Trace element concentrations in the isotopically unique Allende inclusion,EK 1-4-1

Concentrations of rare-earth elements (REE), Sc, Fe, Co, Cr, Na and Ir in the bulk sample and mineral separates of the isotopically unique Allende inclusion, EK 1-4-1, were determined by instrumental neutron activation analysis. REE concentrations were also determined by mass-spectrometric isotope dilution for two density separates.The inclusion showed enrichment of light REE over heavy REE with a positive Yb anomaly, thus showing a tendency to resemble group II fine-grained inclusions in REE abundances, although EK 1-4-1 is a coarse-grained inclusion. High Cr concentrations also indicate group II affinity. However, high Ir (6 ppm) and Sc (105 ppm), and low FeO (1.80%), and Co (13.8 ppm) concentrations in the bulk sample and low Na concentrations in mineral separates show group I affinity.Between melilite and pyroxene fractions, the same samples in which mass-fractionated O isotope ratios were observed (Clayton and Mayeda, 1977), REE, Sc, Co and Fe showed distributions which are substantially different from those observed for “ordinary” Allende type B inclusions. These two minerals do not appear to be in equilibrium with respect to trace element distributions.The results indicate that the isotopically unique EK 1-4-1 is also unusual in its elemental abundances and distributions.