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1.
华北块体、胶辽朝块体与郯庐断裂   总被引:36,自引:5,他引:31  
乔秀夫  张安棣 《中国地质》2002,29(4):337-345
华北块体(NCB)与胶辽朝块体(JLKB)是中朝板块东部从震旦纪(680Ma)开始裂解的两个不同的构造单元。两个块体的界线称古郯庐断裂(PTLF),古郯庐断裂位置与现今郯庐断裂(TLF)相吻合,即由合肥向北延伸,过渤海,经沈阳以东呈NE走向至吉林南部。古郯庐断裂带附近震旦纪碳酸盐岩中的强地震记录及相应的辉绿岩侵位,是中朝板块内部裂解的基本地质证据,古郯庐断裂带(板内地震带)与元古超大陆Rodinia的裂解时期是一致的。两个块体上,太古宙基底岩石不同;元古宙及古生代的发展历史有别,两个块体于晚石炭世的莫斯科期重新闭合。朝鲜半岛中部的临津江带曾被认为是大别-胶南造山带的东延部分,但临津江带只是一般性断裂,胶南超高压带在朝鲜半岛并未发现,朝鲜半岛南部主体与辽东半岛古生界相似,因此,将中朝板块的南界,也是较辽朝块体的南界置于朝鲜半岛之南,它与胶南造山带以黄海转换断层(YSTF)联结。辽宁省瓦房店(旧称复县)与山东省蒙阴含金刚石的金伯利岩分布在郯庐断裂带的东,西两侧,南北方向距离的550km。两地金伯利岩年龄值在500-450Ma之间,即中奥陶世末侵位。鉴于两地金伯利岩在岩相学,矿物学与侵位年龄等某些方面的相似性,又紧邻郯庐断裂两侧,有些地质学家认为二者在侵位时可能相距颇近,属同一岩省,因而将瓦房店与蒙阴两个金伯利岩岩省之间的距离总是用郯庐断裂的巨大平移来解释。郯庐断裂为切过岩石圈的深断裂,对比瓦房店与蒙阴两地岩石圈剖面的异同,应是判断郯庐断裂有无巨大平移的重要依据。通过对金伯利岩中地幔样品的研究,揭示出了两地岩体侵位时所穿越的古岩石圈剖面是很不一致的,表明二者当时并非连接一起或相距甚近图片者结合区域地质构造研究的新认识,发现它们实际是分别侵位于中朝板块的两个不同的构造单元上,两地距离与平移无关,不支持郯庐断裂左行走滑巨大平移的观点,本文期望这种交叉学科研究所提供的材料能有助于讨论中国东部这一巨型断裂系统的性质。  相似文献
2.
Kimberlites from Southern Africa, along with their low-Cr megacrysts,have unusual Hf–Nd isotopic characteristics. Group I andTransitional kimberlites define arrays trending oblique to,and well below, the Nd–Hf isotope ‘mantle array’,defined by oceanic basalts, i.e. they have negative  相似文献
3.
华北地台金伯利岩岩浆活动时代讨论   总被引:11,自引:0,他引:11       下载免费PDF全文
路凤香  赵磊 《岩石学报》1995,11(4):365-374
华北地台金伯利岩岩浆活动可分为三个时期:(1)中元古代金伯利岩和钾镁煌斑岩岩浆活动期,以鄂尔多斯陆核边缘山西阳高岩区为代表(1649~1811Ma);(2)古生代金伯利岩岩浆活动,以冀鲁辽陆核边缘的铁岭岩区、中部的复县和蒙阴岩区为代表(含矿金伯利岩,457~462Ma);(3)中~新生代金伯利岩岩浆活动时期,以鹤壁和涉县岩区为代表(117~52Ma)。含矿金伯利岩岩浆活动与华北地台中奥陶世晚期的造陆抬升作用有关。这类岩浆形成时必须处于克拉通岩石圈底部有小的热扰动以及流体作用的条件,而过高的地温梯度反而起到破坏金刚石保存的作用。  相似文献
4.
在金伯利岩中新发现的几种矿物及其意义   总被引:10,自引:1,他引:9  
新近发现华北地台金伯利岩中存在自然铁、自然铜、自然锡、硅铁石、二硅铁矿、未命名的Si、Fe、Ti互化物及含铬黑镁铁钛矿等前人未曾报导过的矿物。据初步研究,它们与处于强还原环境的地幔深层流体有关。这些矿物的发现,首次为软流层中的流体交代作用提供了实物证据。  相似文献
5.
We present the first data on the petrology of the mantle lithosphereof the Southeastern (SE) Slave craton, Canada. These are basedon petrographic, mineralogical and geochemical studies of mantlexenoliths in Pipe 5034 of the Cambrian Gahcho Kué kimberlitecluster. Major types of mantle xenoliths include altered eclogite,coarse garnet or spinel peridotite, and deformed garnet peridotite.The peridotites belong to the low-temperature suite and formedat T=600–1300°C and P= 25–80 kbar in a thick(at least 220–250 km), cool lithosphere. The SE Slavemantle is cooler than the mantle of other Archaean cratons andthat below other terranes of the Slave craton. The thick lithosphereand the relatively cool thermal regime provide favourable conditionsfor formation and preservation of diamonds beneath the SE Slaveterrane. Similar to average Archaean mantle worldwide, the SESlave peridotite is depleted in magmaphile major elements andcontains olivine with forsterite content of 91–93·5.With respect to olivine composition and mode, all terranes ofthe Slave mantle show broadly similar compositions and are relativelyorthopyroxene-poor compared with those of the Kaapvaal and Siberiancratons. The SE Slave spinel peridotite is poorer in Al, Caand Fe, and richer in Mg than deeper garnet peridotite. Thegreater chemical depletion of the shallow upper mantle is typicalof all terranes of the Slave craton and may be common for thesubcontinental lithospheric peridotitic mantle in general. Peridotiticxenoliths of the SE Slave craton were impregnated by kimberliticfluids that caused late-stage recrystallization of primary clinopyroxene,spinel, olivine and spinel-facies orthopyroxene, and formationof interstitial clinopyroxene. This kimberlite-related recrystallizationdepleted primary pyroxenes and spinel in Al. The kimberliticfluid was oxidizing, Ti-, Fe- and K-rich, and Na-poor, and introducedserpentine, chlorite, phlogopite and spinel into peridotitesat P < 35 kbar. KEY WORDS: kimberlite xenolith; lithosphere; mantle terrane; chemical zoning; thermobarometry; Slave craton  相似文献
6.
Proterozoic mafic potassic and ultrapotassic igneous rocks emplacedin the Cuddapah Basin and Dharwar Craton of the southern Indianshield are among the earliest recorded on Earth. Lamproitesintrude the basin and its NE margin, whereas kimberlites intrudethe craton to the west of the basin. Kimberlites occur in twospatially separate groups: the non-diamondiferous Mahbubnagarcluster that was emplaced at 1400 Ma and is of a similar ageto the Cuddapah lamproites, and the predominantly diamondiferousAnantapur cluster, emplaced at  相似文献
7.
Mineral inclusions in diamonds from the Sputnik kimberlite pipe, Yakutia   总被引:8,自引:0,他引:8  
The Sputnik kimberlite pipe is a small “satellite” of the larger Mir pipe in central Yakutia (Sakha), Russia. Study of 38 large diamonds (0.7-4.9 carats) showed that nine contain inclusions of the eclogitic paragenesis, while the remainder contain inclusions of the peridotitic paragenesis, or of uncertain paragenesis. The peridotitic inclusion suite comprises olivine, enstatite, Cr-diopside, chromite, Cr-pyrope garnet (both lherzolitic and harzburgitic), ilmenite, Ni-rich sulfide and a Ti-Cr-Fe-Mg-Sr-K phase of the lindsleyite-mathiasite (LIMA) series. The eclogitic inclusion suite comprises omphacite, garnet, Ni-poor sulfide, phlogopite and rutile. Peridotitic ilmenite inclusions have high Mg, Cr and Ni contents and high Nb/Zr ratios; they may be related to metasomatic ilmenites known from peridotite xenoliths in kimberlite. Eclogitic phlogopite is intergrown with omphacite, coexists with garnet, and has an unusually high TiO2 content. Comparison with inclusions in diamonds from Mir shows general similarities, but differences in details of trace-element patterns. Large compositional variations among inclusions of one phase (olivine, garnet, chromite) within single diamonds indicate that the chemical environment of diamond crystallisation changed rapidly relative to diamond growth rates in many cases. P-T conditions of formation were calculated from multiphase inclusions and from trace element geothermobarometry of single inclusions. The geotherm at the time of diamond formation was near a 35 mW/m2 conductive model; that is indistinguishable from the Paleozoic geotherm derived by studies of xenoliths and concentrate minerals from Mir. A range of Ni temperatures between garnet inclusions in single diamonds from both Mir and Sputnik suggests that many of the diamonds grew during thermal events affecting a relatively narrow depth range of the lithosphere, within the diamond stability field. The minor differences between inclusions in Mir and Sputnik may reflect lateral heterogeneity in the upper mantle.  相似文献
8.
山东蒙阴金伯利岩侵位年代研究新成果   总被引:8,自引:2,他引:6  
报道了山东蒙阴金伯利岩全岩及单矿物Rb-Sr同位素的系统定年结果,认为全岩—基质金云母Rb-Sr等时线年龄值(560Ma±10Ma)代表了蒙阴金伯利岩岩浆侵位的主要活动期。  相似文献
9.
Crystallization temperatures (T) and oxygen fugacities (fO2)of kimberlite magma are estimated from oxides included in olivinephenocrysts from the Leslie, Aaron, Grizzly and Torrie kimberlitepipes in the central Slave Province, Canada. Crystallizationtemperatures recorded by olivine–chromite pairs at anassumed pressure of 1·0 GPa are 1030–1170°C± 50°C, with a mean of  相似文献
10.
Chemical compositions were determined on mineral inclusions recovered from 290 microdiamonds (<1 mm) from 8 operating diamond mines in Yakutia. The sampled diamond mines include Mir, Udachnaya, Internatsionalnaya, Aykhal, Sytykanskaya, Yubileynaya, Komsomolskaya and Krasnopresnenskaya. The mineral inclusions include both ultramafic (peridotitic) suite (U-type) and eclogitic suite (E-type) examples. Olivines, chromites, Cr-pyropes, Cr-diopsides and enstatite were studied from U-type diamonds. Mg–Ca–Fe-garnets and omphacitic clinopyroxenes were studied from E-type microdiamonds. Abundances and compositions of these inclusions were compared with published and unpublished data on inclusions available from approximately 2000 macrodiamonds (>1 mm) from the same sources, and worldwide data for olivines and chromites. Although there are general similarities, notable exceptions were detected in about 10% of the inclusions from microdiamonds. For each of the pipes, anomalous compositions occur between the micro- and macrodiamond inclusions, but in different proportions, sometimes as high as 50% of the inclusions. Our study has demonstrated that mineral inclusions in microdiamonds are considerably more variable in their compositions and parageneses compared with inclusions in macrodiamonds.

Significant compositional anomalies in inclusions from microdiamonds include: (1) garnets containing pyroxene solid solution (majoritic component) both in U- and E-type microdiamonds from three pipes: Yubileynaya, Komsomolskaya and Krasnopresnenskaya. The moles of Si (pfu) in these garnets range from 3.07 to 3.13 and as high as 3.29, on the basis of 12 oxygens, along with a notable contents of Na2O in two eclogitic garnets (0.43 and 0.93 wt.%) and uniquely high Cr2O3 and CaO contents in an ultramafic garnet of wehrlitic paragenesis; (2) coexisting wehrlitic garnets in a single microdiamond, one majoritic, the other normal, both with distinct +Eu anomalies, considered as signatures of crustal protoliths for the precursors to these garnets; (3) olivines with relatively low Fo (86–89) and high-NiO contents (0.46–0.64 wt.%), from Yubileynaya and Sytykanskaya microdiamonds; (4) chromites containing high-TiO2 (up to 4.7 wt.%) and some extremely rich in MgO (Mg# 80). It is concluded that many of these compositional features observed may be related to a deeper origin for the microdiamond source region (>300 km), for at least a 10–30% portion of microdiamonds from each Yakutian pipe.  相似文献

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