共查询到20条相似文献，搜索用时 62 毫秒
1.
为详细探讨含钠长石翡翠的成因机制,笔者选取了若干来自缅甸的含钠长石翡翠,对其进行了详细的岩相学、矿物化学等方面的研究。含钠长石翡翠样品属于豆青种,主要由硬玉、钠长石、方沸石和少量的多硅白云母、钡铝硅酸盐等矿物组成。其中的硬玉发育清晰的环带结构,成分从核部至边缘发生规律性的成分变化。翡翠同时受到两期后期流体活动的改造,第一期以钠长石为代表,第二期以方沸石为代表,流体的改造作用使硬玉呈现碎裂状、碎斑状结构和交代穿孔等结构。结果表明,含钠长石翡翠样品表现出从成岩流体中直接结晶的特点,该流体富集Na、Al、Si、K、Ba以及少量的Ca、Fe、Mg等元素,微量元素则相对富集LREE、HFSE和sr等元素。结合前人的研究结果以及该玉石中的矿物反应关系,笔者推测缅甸翡翠形成的压力和温度范围分别在6-14kbar和300℃-450℃。 相似文献
2.
缅甸是世界上优质翡翠的最重要产地,角闪石族矿物是缅甸翡翠中的常见矿物。对缅甸翡翠原石进行手标本、薄片偏光显微镜观察和电子探针测试,结果表明,翡翠原石组成矿物的形成顺序为岩浆锆石→热液锆石和硬玉→绿辉石→Ca质角闪石→Na-Ca、Na质角闪石→钠长石,岩石形成后受到后期应力作用使部分角闪石族矿物发生变形。Ca质角闪石形成后,晚期Na-Al-Si流体和富Ca、Mg和Fe的浅闪石发生反应,形成了Na-Ca质、Na质角闪石,包括钠透闪石,蓝闪石和镁铝钠闪石。随压力的降低,残余流体在早期形成矿物颗粒之间沉淀结晶出钠长石。矿物的化学成分和矿物种类及结构对翡翠的品质有重要影响,硬玉中的Cr及角闪石矿物的存在导致了翡翠绿色深浅的变化。组成矿物的形态及颗粒大小、排列的紧密程度,影响翡翠的质地和透明度等外观特征。 相似文献
3.
4.
金寨响洪甸碱性侵入岩体分布在大别造山带东北缘的北淮阳地区,侵位于上元古界青白口系佛子岭群中。主要岩石类型为正长岩(似斑状正长岩)、碱性正长岩和霞石正长岩。正长岩的主要矿物为碱性长石及少量黑云母、普通辉石、绿钙闪石;碱性正长岩包含钾长石、角闪石、辉石和少量黑云母;霞石正长岩主要由碱性长石、霞石及少量绿钙闪石、普通辉石、次透辉石等矿物组成。化学成分上均具有偏铝质、富碱、高钾、贫钛的特点。富集大离子亲石元素K、Rb、U、Nd和轻稀土元素La、Ce、Pr、Nd、Sm,亏损高场强元素Nb、Ta、P、Ti,轻、重稀土元素比值及La/Nb、Ba/Nb值较高,呈弱的负铕异常。根据高精度同位素年代学测试结果,响洪甸碱性侵入岩成岩期次分为2期:早期霞石正长岩,LA-ICP-MS锆石U-Pb年龄为(135.1±0.7)Ma;晚期正长岩,SHRIMP锆石U-Pb年龄为(125.0±1)Ma和碱性正长岩,颗粒锆石U-Pb年龄为122.3 Ma。主体岩石似斑状正长岩的Hf同位素分析结果表明,其初始176Hf/177Hf比值为0.282 243~0.282 404,εHf(t)为-10.376~-16.602,结合该岩体的Sr-Nd同位素地球化学特征,推测响洪甸碱性侵入岩是富集地幔部分熔融的产物,其源区可能有部分陆壳物质的参与。其形成的构造背景为后碰撞的伸展环境。 相似文献
5.
翡翠的概念,分类及A,B,C货鉴定有关问题的讨论 总被引：1，自引：0，他引：1
翡翠为达宝玉石级的、主要由矿物硬玉或含硬玉分子较高的、其他辉石类矿物构成的集合体。翡翠不等于硬玉,也不等于硬玉岩,同意英译名为Ｆｅｉｃｕｉ。翡翠的分类主要是按矿物成分分类,可分为：（１）以玉矿物为主的翡翠,硬玉矿≥８０％称为硬玉翡翠,简称翡翠;〈８０％￣≥５０％时,可将重要的伴生矿物名称作为形容词加于基本名称“硬玉翡翠”前。（２）其他含硬玉分子较高的钠质辉石为主的翡翠,如绿辉石翡翠、铬硬玉翡翠、铁 相似文献
6.
《新疆地质》2021,(2)
蒙其克辉长岩脉位于玛因鄂博断裂带南缘,属喀拉通克岩体一部分。以蒙其克辉长岩脉中黑云母及角闪石为研究对象,在岩相学观察基础上,利用电子探针对岩体中黑云母和角闪石进行矿物成分分析,限定岩体形成的温压条件、岩浆氧逸度及含水量等结晶条件,探讨岩浆演化及成岩过程。数据显示,辉长岩脉中黑云母矿物Fe~(2+)/(Mg+Fe~(2+))变化范围为0.27～0.33,具富镁(Mg O=16.01%～17.45%)、富铝(Al_2O_3=14.35%～15.75%)、贫钛(Ti O_2=1.69%～2.57%)、贫钙(Ca O=0.19%～0.56%)特征,属镁质黑云母。角闪石矿物具富镁(Mg O=10.48%～15.15%)、富钙(Ca O=10.26%～11.90%)、贫钾(K_2O=0.39%～1.14%)及富钠(Na_2O/K_2O1.0)特征,属镁角闪石和浅闪石。通过电子探针分析黑云母及角闪石矿物化学成分,经化学式计算矿物结晶温度分别为646.97℃～707.82℃和766.27℃～902.38℃;成岩压力分别为147.84～220.87 MPa和85.0 1～297.40 MPa;侵位深度分别为5.59～8.35 km和3.21～11.24 km;氧逸度logf _(O2)分别为-18.54～-16.49和-13.00～-10.49;同时,角闪石结晶时熔体中含水量为5.26%～6.96%。矿物成分相关比值及图解反映成岩物质主要来源于壳幔混合源,为钙碱性岩浆,蒙其克辉长岩脉的形成与俯冲作用关系密切。 相似文献
7.
8.
大兴安岭北部诺敏河地幔金云母及钾质地幔熔体研究 总被引：2，自引：1，他引：1
在大兴安岭北部诺敏河第四纪钾质火山岩携带的地幔捕虏体中,发现少量金云母矿物和富钾地幔熔体。金云母颗粒大小1~5mm,呈网脉状充填在橄榄石和辉石、石榴子石等地幔矿物间隙。电子探针研究表明地幔橄榄石、单斜辉石、斜方辉石和石榴石等矿物几乎不含钾质成分(K2O0.01%),而金云母矿物成分具有高钾(K2O~10%)、高钛(Ti O25.41%~7.74%)的特点,暗示区域地幔钾的富集与金云母矿物有密切关系。地幔金云母的成因往往与富钾地幔流体/熔体的交代作用有关,在地幔捕虏体矿物反应边的硅酸盐熔体(囊体)中,发现富硅、富钾的熔体,K2O 4%~8%。结合前人地幔熔体研究,认为区域地幔经历了多期、不同成分地幔熔体的富集作用,其中富钾熔体对地幔钾质成分的富集起到重要作用。诺敏钾质火山正是富钾地幔部分熔融的产物,钾质熔体成分的来源可能与俯冲再循环的壳源物质有关。 相似文献
9.
安徽金寨响洪甸碱性侵入岩年代学、岩石地球化学及其意义 总被引：4，自引：0，他引：4
金寨响洪甸碱性侵入岩体分布在大别造山带东北缘的北淮阳地区,侵位于上元古界青白口系佛子岭群中。主要岩石类型为正长岩（似斑状正长岩）、碱性正长岩和霞石正长岩。正长岩的主要矿物为碱性长石及少量黑云母、普通辉石、绿钙闪石;碱性正长岩包含钾长石、角闪石、辉石和少量黑云母;霞石正长岩主要由碱性长石、霞石及少量绿钙闪石、普通辉石、次透辉石等矿物组成。化学成分上均具有偏铝质、富碱、高钾、贫钛的特点。富集大离子亲石元素K、Rb、U、Nd和轻稀土元素La、Ce、Pr、Nd、Sm,亏损高场强元素Nb、Ta、P、Ti,轻、重稀土元素比值及La/Nb、Ba/Nb值较高,呈弱的负铕异常。根据高精度同位素年代学测试结果,响洪甸碱性侵入岩成岩期次分为2期：早期霞石正长岩,LA-ICP-MS锆石U-Pb年龄为（135.1±0.7） Ma;晚期正长岩,SHRIMP 锆石U-Pb年龄为（125.0±1） Ma和碱性正长岩,颗粒锆石U-Pb年龄为122.3 Ma。主体岩石似斑状正长岩的Hf同位素分析结果表明,其初始 176Hf/177Hf 比值为0.282 243~0.282 404,εHf（t）为-10.376~-16.602,结合该岩体的Sr-Nd同位素地球化学特征,推测响洪甸碱性侵入岩是富集地幔部分熔融的产物,其源区可能有部分陆壳物质的参与。其形成的构造背景为后碰撞的伸展环境。 相似文献
10.
11.
Stephen K. Donovan David A.T. Harper Roger W. Portell Willem Renema 《Proceedings of the Geologists' Association. Geologists' Association》2014
The Late Oligocene oyster Hyotissa antiguensis (Brown) is locally common in the Antigua Formation of Hughes Point, eastern Antigua, Lesser Antilles; it was not commonly bored at that time. Its valves and shells are robust, and reworked into the shallow water near-shore environment in Antigua; it could potentially be incorporated into younger rocks. Its neoichnology includes clues that would facilitate identification of these oysters as reworked fossils. The suite of modern borings found in these specimens includes common Caulostrepsis taeniola Clarke, Gastrochaenolites isp. cf. G. turbinatus Kelly and Bromley and Entobia isp., and rare Oichnus simplex Bromley and Rogerella? isp. The latter three taxa are limited to oyster shell substrates. Of the common ichnotaxa, Caulostrepsis and Gastrochaenolites are particularly prominent in limestone clasts and limestone cemented to oyster shells, which would be an indicator of reworking if found in a post-Oligocene lithified deposit. Caulostrepsis and Gastrochaenolites are relatively less common in oyster shells and valves, and in many specimens are seen to terminate against the shell. Entobia is the only common boring limited to the shell substrate. The fidelity of preservation of modern borings is also superior in limestone clasts. This suite of borings is comparable with those found in the Neogene of the Antillean region. 相似文献
12.
Fabien Knoll Gilles Cuny Pierre-Olivier Mojon Raquel López-Antoñanzas 《Proceedings of the Geologists' Association. Geologists' Association》2014
The palaeontological content (charophytes and vertebrates) of organic-rich layers from the Middle Jurassic (Bathonian) of the Grands Causses at Mostuéjouls (Aveyron, France) has been examined. It is rich in gyrogonites of Porochara douzensis. The vertebrates of the lower layer include a single hybodontiform tooth, “semionotiform” teeth and scales, and one pycnodontiform tooth whereas the upper layer has yielded one hybodontiform tooth, a variety of actinopterygian remains (mostly Caturus sp. and indeterminate pycnodontiforms) and a few possible reptile remains. The variation in fauna between the two layers is ascribed to a different degree of marine influence. 相似文献
13.
Stephen K. Donovan James Isted 《Proceedings of the Geologists' Association. Geologists' Association》2014
Nineteenth-century references to clavate borings in woody substrates in the Lower Greensand of the Isle of Wight used a variety of names, but Teredo (a wood-boring bivalve, not a boring), Teredolithes (a junior synonym of Teredolites) and Gastrochaena (a bivalve borer of rock and shelly substrates, not a boring in wood) are all nomenclatorially incorrect. Borings in a beach clast derived from the Lower Greensand Group and recently collected from Sandown Bay, Isle of Wight, are referred to Teredolites isp. cf. T. longissimus Kelly and Bromley. This specimen confirms the presence of Teredolites in the Lower Greensand Group and demonstrates a common ichnological problem of beach clasts; borings, either fossil or modern, are incompletely preserved, making confident classification below the level of ichnogenus problematic. 相似文献
14.
Indigofera melanadenia and Tephrosia longipes plant species, collected from Cu–Ni mining area, were evaluated for accumulation of Cu and Ni. The total and bioavailable concentrations of Cu and Ni in the host soils were also determined. Flame Atomic Absorption Spectrometry was used for all metal determinations. The total and bioavailable concentrations of Cu in the soils were in the range 900–9000 μg/g and 200–2000 μg/g respectively. For Ni, the total and bioavailable concentrations were in the range 900–2000 μg/g and ∼ 40–100 μg/g respectively. The concentrations of Cu and Ni in the leaves of I. melanadenia were higher than in the roots with a range 80–130 μg/g in the leaves and 20–80 μg/g in the roots for Cu and a range of 150–200 μg/g in the leaves and 20–60 μg/g in the roots for Ni. Concentration of Cu in T. longipes was in the range of 37–240 μg/g and 150–200 μg/g in the leaves and roots respectively while the concentration of Ni was 80–140 μg/g in the leaves and 25–100 μg/g in the roots. Results indicate that both species have a potential for accumulating Cu and Ni. Translocation factor, a ratio of shoots to roots metal concentration, was used to evaluate the translocation properties of the plants from roots to shoots. Translocation factors of the plants were ≥ 1 suggesting efficient translocation of metals from roots to shoots. 相似文献
15.
16.
The origin of the genus Bos is a debated issue. From ∼ 0.5 Ma until historic times, the genus is well known in the Eurasian large mammal assemblages, where it is represented by Bos primigenius. This species has a highly derived cranial anatomy that shows important morphological differences from other Plio-Pleistocene Eurasian genera of the tribe Bovini such as Leptobos, Bison, Proamphibos-Hemibos, and Bubalus. The oldest clear evidence of Bos is the skull fragment ASB-198-1 from the middle Pleistocene (∼ 0.6-0.8 Ma) site of Asbole (Lower Awash Valley, Ethiopia). The first appearance of Bos in Europe is at the site of Venosa-Notarchirico, Italy (∼ 0.5-0.6 Ma). Although the origin of Bos has traditionally been connected with Leptobos and Bison, after a detailed anatomical and morphometric study we propose here a different origin, connecting the middle Pleistocene Eurasian forms of B. primigenius with the African Late Pliocene and early Pleistocene large size member of the tribe Bovini Pelorovis sensu stricto. The dispersal of the Bos lineage in Western Europe during middle Pleistocene times seems to coincide with the arrival of the Acheulean tool technology in this continent. 相似文献
17.
Vegetation and climate change on the Bolivian Altiplano between 108,000 and 18,000 yr ago 总被引：1，自引：0，他引：1
Alex Chepstow-Lusty Mark B. Bush Paul A. Baker Sherilyn C. Fritz James Aronson 《Quaternary Research》2005,63(1):90-98
A 90,000-yr record of environmental change before 18,000 cal yr B.P. has been constructed using pollen analyses from a sediment core obtained from Salar de Uyuni (3653 m above sea level) on the Bolivian Altiplano. The sequence consists of alternating mud and salt, which reflect shifts between wet and dry periods. Low abundances of aquatic species between 108,000 and 50,000 yr ago (such as Myriophyllum and Isoëtes) and marked fluctuations in Pediastrum suggest generally dry conditions dominated by saltpans. Between 50,000 yr ago and 36,000 cal yr B.P., lacustrine sediments become increasingly dominant. The transition to the formation of paleolake “Minchin” begins with marked rises in Isoëtes and Myriophyllum, suggesting a lake of moderate depth. Similarly, between 36,000 and 26,000 cal yr B.P., the transition to paleolake Tauca is also initiated by rises in Isoëtes and Myriophyllum; the sustained presence of Isoëtes indicates the development of flooded littoral communities associated with a lake maintained at a higher water level. Polylepis tarapacana-dominated communities were probably an important component of the Altiplano terrestrial vegetation during much of the Last Glacial Maximum (LGM) and previous wet phases. 相似文献
18.
William T. Blows Kerri Honeysett 《Proceedings of the Geologists' Association. Geologists' Association》2014
A new partial skeleton of the armoured ornithischian dinosaur Polacanthus found in the Wadhurst Clay Formation (Valanginian stage) of Bexhill, Sussex is the oldest recorded occurrence of this taxon. Previous discoveries suggested that at least two armoured ornithischians occur in the Wealden succession: Polacanthus, which was mostly restricted to the Barremian, and Hylaeosaurus, which was recorded as present only in the Valanginian. The new discovery extends the stratigraphic range of Polacanthus into the Valanginian. Although these two taxa appear to be closely similar anatomically, their osteology now suggests they are not synonymous. The new specimen includes the first known jugal as well as a comparatively rare polacanthid plate/spine (splate) which probably comes from the shoulder (pectoral) area of these animals. 相似文献
19.
Kyanite-rich and quartz-rich eclogites occur as lenses within amphibolite-facies quartzo-feldspathic gneisses in the Pohorje Mountains, Northern Slovenia, that form the easternmost Austroalpine basement. Major and trace elements indicate that the kyanite-rich eclogites were derived from plagioclase-rich gabbroic cumulates, whereas the quartz-rich eclogites represent more fractionated basaltic compositions. Both varieties are characterized by a LREE-depleted N-MORB type REE signature. Geothermobarometry and P-T pseudosections indicate that eclogites equilibrated at 1.8-2.5 GPa and 630-700 °C, consistently with the lack of coesite and with equilibration conditions of the chemically similar eclogites from the adjacent basement units at Koralpe and Saualpe type localities. Decompression reaction textures include (i) clinopyroxene-plagioclase intergrowths after omphacite, (ii) replacement of kyanite by corundum-plagioclase-spinel±sapphirine symplectites, (iii) breakdown of phengite to biotite-plagioclase sapphirine symplectites. The results of this study indicate that Koralpe, Saualpe and Pohorje high-pressure rocks represent former MORB-type oceanic crust that was subducted in the course of the late Cretaceous (approximately 100 Ma ago) collision between the European and the Apulian plates. 相似文献
20.
缅甸硬玉岩地区的热液型钠长石岩 总被引：2，自引：0，他引：2
产于俯冲带内的低温高压带的由单矿物构成的硬玉岩通常伴有钠长石岩,目前对于硬玉岩研究的关注度较高,而对于钠长石岩则相对较低,很少有相关论文报导.产于缅甸翡翠矿区的钠长石岩,经常与硬玉岩相伴而生,是良好的研究样品.钠长石岩的主要矿物成分是低温钠长石,其次含有硬玉、绿辉石、透辉石等辉石类矿物和钠透闪石、蓝透闪石、镁钠闪石等闪石类矿物,此外还有钠沸石等.钠长石沿着解理和裂隙交代硬玉,说明钠长石形成晚于硬玉岩.钠长岩中的主要组成矿物钠长石的形成温度小于300℃,且其形成压力小于0.5kb,推测是在硬玉岩抬升程中通过交代与沉淀作用形成.其内的透辉石有两种类型,一类可能是被交代的硬玉中的透辉石组分会渐进增加,最终形成透辉石.另一类是被绿辉石包裹的透辉石残留,其很有可能是早期来自地幔楔或者俯冲带岩石中的矿物残留,即异剥钙榴岩或辉石岩类,可以视作硬玉化绿辉石岩和硬玉化异剥钙榴岩的矿物学证据.热液型钠长石岩的存在进一步说明缅甸翡翠矿区钠化热液存在现象的普遍性与穿越性. 相似文献