全文获取类型
收费全文 | 131篇 |
免费 | 24篇 |
国内免费 | 56篇 |
专业分类
地球物理 | 21篇 |
地质学 | 181篇 |
海洋学 | 3篇 |
天文学 | 1篇 |
综合类 | 5篇 |
出版年
2024年 | 2篇 |
2023年 | 3篇 |
2022年 | 2篇 |
2021年 | 6篇 |
2020年 | 4篇 |
2019年 | 6篇 |
2018年 | 3篇 |
2017年 | 5篇 |
2016年 | 4篇 |
2015年 | 7篇 |
2014年 | 8篇 |
2013年 | 12篇 |
2012年 | 3篇 |
2011年 | 12篇 |
2010年 | 4篇 |
2009年 | 10篇 |
2008年 | 10篇 |
2007年 | 7篇 |
2006年 | 10篇 |
2005年 | 14篇 |
2004年 | 9篇 |
2003年 | 6篇 |
2002年 | 5篇 |
2001年 | 8篇 |
2000年 | 6篇 |
1999年 | 6篇 |
1998年 | 5篇 |
1997年 | 7篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有211条查询结果,搜索用时 484 毫秒
21.
22.
Intracrystal microtextures formed by a process of mutual replacement in alkali feldspars record fluid–rock reactions that
have affected large volumes of the Earth’s crust. Regular, ≤1 μm-scale ‘strain-controlled’ perthitic microtextures coarsen,
by up to 103, by a dissolution–reprecipitation process, producing microporous patch or vein perthites on scales >100 μm. We have developed
earlier studies of such reactions in alkali feldspar cm-scale primocrysts in layered syenites from the Klokken intrusion,
South Greenland. We present new hyperspectral CL, SEM images, and laser ICPMS analytical data, and discuss the mechanism of
such replacement reactions. The feldspars grew as homogeneous sodic sanidines which unmixed and ordered by volume diffusion
during cooling into the microcline field at ~450°C, giving regular, fully coherent ‘braid’ cryptoperthite. At ≤450°C the crystals
reacted with a circulating post-magmatic aqueous fluid. The braid perthite behaved as a single reactant ‘phase’ which was
replaced by two product phases, incoherent subgrains of low albite and microcline, with micropores at their boundaries. The
driving force for the reactions was coherency strain energy, which was greater than the surface energy in the subgrain mosaic.
The external euhedral crystal shapes and bulk major element composition of the primocrysts were unchanged but they became
largely pseudomorphs composed of subgrains usually with the ‘pericline’ and ‘adularia’ habits (dominant {110} and subordinate
{010} morphology) characteristic of low T growth. The subgrains have an epitactic relationship with parent braid perthite. Individual subgrains show oscillatory zoning
in CL intensity, mainly at blue wavelengths, which correlates with tetrahedral Ti. Regular zoning is sometimes truncated by
irregular, discordant surfaces suggesting dissolution, followed by resumption of growth giving regular zoning. Zones can be
traced through touching subgrains, of both albite and microcline, for distances up to ~500 μm. At ≤340°C, the microcline subgrains
underwent a third stage of unmixing to give straight lamellar film perthites with periodicities of ~1 μm, which with further
cooling became semicoherent by the development of spaced misfit dislocations. Sub-grain growth occurred in fluid films that
advanced through the elastically strained braid perthite crystals, which dissolved irreversibly. Braid perthite was more soluble
than the strain-free subgrain mosaics which precipitated from the supersaturated solution. Some volumes of braid texture have
sharp surfaces that suggest rapid dissolution along planes with low surface energies. Others have complex, diffuse boundaries
that indicate a phase of coherent lamellar straightening by volume diffusion in response to strain relief close to a slowly
advancing interface. Nucleation of strain-free subgrains was the overall rate-limiting step. To minimise surface energy subgrains
grew with low energy morphologies and coarsened by grain growth, in fluid films whose trace element load (reflected in the
oscillatory zoning) was dictated by the competitive advance of subgrains over a range of a few tens of mm. The cross-cutting
dissolution surfaces suggest influxes of fresh fluid. Removal of feldspar to give 2 vol% porosity would require a feldspar:fluid
ratio of ~1:26 (by wt). The late reversion to strain-controlled exsolution in microcline subgrains is consistent with loss
of fluid above 340°C following depressurization of the intrusion. A second paper (Part II) describes trace element partitioning
between the albite and microcline subgrains, and discusses the potential of trace elements as a low-T geothermometer.
This paper and the Part II are dedicated in memory of J.V. Smith and W.L. Brown, both of whom died in 2007, in acknowledgement
of their unrivalled contributions to the study of the feldspar minerals over more than half a century. 相似文献
23.
从湖南省北部赤山岛枫树嘴旧石器遗址剖面第2、第3和第4考古层位采集的3个沉积物样品中提取的细粒混合矿物,尝试对其红外释光(IRSL)信号进行研究。实验表明,虽然长石IRSL信号很弱,但仍可以测得信噪比足够高的红外激发后高温红外激发释光(post-IR IRSL)信号。与此同时,样品存在明显的红外激发后蓝光释光(post-IR OSL)信号,并且样品的IRSL与post-IR OSL信号均以快组分为主,这为该地区沉积物利用长石光释光信号定年提供了新的可能。鉴于长石IRSL信号较弱,根据剂量恢复实验结果,本研究采用post-IR IRSL SAR法(50℃红外激发后270℃高温红外激发,pIRIR270℃)进行等效剂量测量,同时也应用post-IR OSL SAR法定年进行比较。实验结果表明,细粒混合矿物的pIRIR270℃等效剂量分别为418.8±13.2 Gy、562.3±18.2 Gy和694.8±17.9 Gy,相对应的post-IR OSL SAR等效剂量结果为345.0±29.4 Gy、409.6±33.7 Gy和424.7±32.2 Gy。假设强烈化学风化未对沉积物的剂量率造成很大影响,基于长石pIRIR270℃信号的释光年龄为89±6 ka、118±8 ka和152±9 ka,比前人所得的石英OSL SAR法年龄老30%~55%(约20~55 ka)。通过对比不同测量条件下获得的等效剂量值来评估长石IRSL信号是否存在晒退问题,没有发现长石post-IR IRSL信号存在晒退不完全的证据。根据本研究post-IR IRSL SAR法测年结果,赤山岛枫树嘴旧石器遗址似阿舍利技术类型的石器出现在倒数第二次冰期(MIS 6)后期至末次间冰期(MIS 5)前期,比湖南道县福岩洞现代人类牙齿化石年龄(80~120 ka)稍老。作为似阿舍利技术石器制造者的赤山岛古人与福岩洞现代人的关系将是我国旧石器时代考古学和古人类学研究的一个重要课题。 相似文献
24.
通过对薄杖子钾长石矿地质特征分析,阐述了该矿床的成因类型,为中酸性侵入岩型。钾长石矿严格受沿断裂侵入的燕山期碱性正长岩小岩株控制,通过岩浆结晶分离作用而形成,区内矿体基本裸露于地表,地表出露体呈零星分布,矿体形态均不规则。矿体的主要矿物为钾长石,次要矿物为石英、条纹长石、绢云母、黑云母、角闪石,副矿物为黄铁矿、磁铁矿。矿石自然类型为碱性正长岩型,工业类型为玻璃及建筑陶瓷用钾长石矿,开发利用方向为玻璃及建筑陶瓷工业原料。 相似文献
25.
Alfons M. van den Kerkhof Geoffrey H. Grantham 《Contributions to Mineralogy and Petrology》1999,137(1-2):115-132
In the Port Edward area of southern Kwa-Zulu Natal, South Africa, charnockitic aureoles up to 10 m in width in the normally
garnetiferous Nicholson's Point Granite, are developed adjacent to intrusive contacts with the Port Edward Enderbite and anhydrous
pegmatitic veins. Mineralogical differences between the country rock and charnockitic aureole suggest that the dehydration
reaction Bt + Qtz → Opx + Kfs + H2O and the reaction of Grt + Qtz → Opx + Pl were responsible for the charnockitization. The compositions of fluid inclusions
show systematic variation with: (1) the Port Edward Enderbite being dominated by CO2 and N2 fluid inclusions; (2) the non-charnockitized granite by saline aqueous inclusions with 18–23 EqWt% NaCl; (3) the charnockitic
aureoles by low-salinity and pure water inclusions (<7 EqWt% NaCl); (4) the pegmatites by aqueous inclusions of various salinity
with minor CO2. As a result of the thermal event the homogenization temperatures of the inclusions in charnockite show a much larger range
(up to 390 °C) compared to the fluid inclusions in granite (mostly <250 °C). Contrary to fluid-controlled charnockitization
(brines, CO2) which may have taken place along shear zones away from the intrusive body, the present “proximal” charnockitized granite
formed directly at the contact with enderbite. The inclusions indicate contact metamorphism induced by the intrusion of “dry”
enderbitic magma into “wet” granite resulting in local dehydration. This was confirmed by cathodoluminescence microscopy showing
textures indicative for the local reduction of structural water in the charnockite quartz. Two-pyroxene thermometry on the
Port Edward Enderbite suggests intrusion at temperatures of ∼1000–1050 °C into country rock with temperature of <700 °C. The
temperature of aureole formation must have been between ∼700 °C (breakdown of pyrite to form pyrrhotite) and ∼1000 °C. Charnockitization
was probably controlled largely by heat related to anhydrous intrusions causing dehydration reactions and resulting in the
release and subsequent trapping of dehydration fluids. The salinity of the metamorphic fluid in the contact zones is supposed
to have been higher at an early stage of contact metamorphism, but it has lost its salt content by K-metasomatic reactions
and/or the preferential migration of the saline fluids out of the contact zones towards the enderbite. The low water activity
inhibited the localized melting of the granite. Mineral thermobarometry suggests that after charnockite aureole genesis, an
isobaric cooling path was followed during which reequilibration of most of the aqueous inclusions occurred.
Received: 8 November 1998 / Accepted: 21 June 1999 相似文献
26.
Euhedral, post-depositional albite from the Eastern and Western Alps, the western Carpathians and some Greek islands was examined petrographically and geochemically to gain insights into the nature of feldspar reactions in carbonate rocks. This study focuses on coarsely crystalline, homogeneously nucleated albite in order to avoid problems related to the presence of inseparable detrital material in fine-grained albite varieties. All albite samples show a very restricted compositional variability and are typically ≥ 99 mol% Ab component. Unit-cell parameters determined by Rietveld analysis are slightly more variable than previously accepted, but confirm high Al–Si ordering characteristic of low albite. The oxygen isotopic composition of albite ranges from + 19·4‰ to + 28·3‰ VSMOW. There is no direct relationship between the δ18 O value and the inferred temperature of albite formation, nor is there one with stoichiometry. The coarse crystal size (up to several millimetres in diameter), petrographic evidence showing albite cross-cutting stylolites, greater abundance of albite in carbonate rocks subject to high-grade diagenetic or weak metamorphic overprinting and available fluid inclusion data suggest that albite precipitation is favoured at higher temperatures in carbonates than in sandstones. Pore fluids were invariably brines, as suggested by the inferred high positive δ18 Ofluid values, the common association of albite-bearing carbonates and evaporites and reports of saline fluid inclusions in albite. The presence of authigenic albite may thus be a useful tracer of palaeobrine–carbonate reactions, particularly in deep-burial and incipient metamorphic settings. 相似文献
27.
在鲁西地区新太古代晚期(五台期)峄山花岗岩的黑石查和望子山花岗质岩体的岩石中,钾长石粗大斑晶内有自形程度较高的斜长石等矿物包裹体沿其环带定向排列.根据野外观察及岩石、矿物学特征测试分析,钾长石斑晶属于岩浆结晶形成的原生斑晶,受化学成分及侵位结晶过程中的物理化学条件影响,钾长石的生长速度大于其成核密度,因而形成粗大斑晶.估算岩浆温度>950℃,钾长石斑晶快速生长时岩浆温度为750℃,过冷度△T≈150℃,基质结晶时岩浆温度为600℃,△T≈300℃. 相似文献
28.
We investigated the infrared stimulated luminescence (IRSL) and post-infrared IRSL (pIRIR) signals emitted by K-feldspars from sedimentary samples from Asia, Europe and Africa using a single-aliquot multiple elevated temperature (MET) stimulation procedure. For separate aliquots of the same sample, we show that variation among the dose response curves (DRCs), or growth curves, constructed from the regenerative dose signal (Lx), the test dose signal (Tx, an indicator of luminescence sensitivity) and the sensitivity-corrected signal (Lx/Tx) can be largely eliminated by normalising the DRCs using one of the regenerative dose signals; we call this procedure ‘regenerative-dose normalisation’ or re-normalisation. Furthermore, for the MET-pIRIR signals measured at 250 °C, we find that different samples have re-normalised DRCs that follow the same growth function, despite the samples differing significantly in terms of their geological provenance, sedimentary context, equivalent dose (De) and luminescence sensitivity. This common feature offers the potential to establish a ‘global standardised growth curve’ (gSGC) for different samples of K-feldspar, and thereby enable De values to be estimated for a large number of single aliquots by projecting the re-normalised natural signals on to the gSGC. For the 18 samples investigated in this study, we find that De estimates obtained from the gSGC are consistent with those obtained using full single-aliquot regenerative dose (SAR) procedures for doses of up to ∼1600 Gy. The establishment of a gSGC would greatly reduce the time required to date older samples using K-feldspar, as regenerative doses of several hundreds to a few thousands of Gy are typically delivered to each aliquot in each SAR cycle. 相似文献
29.
The Wulanmulun site found in 2010 is an important Paleolithic site in Ordos (China), from which lots of stone and bone artifacts and mammalian fossils have been recovered. It was previously dated by radiocarbon and optically stimulated luminescence (OSL) techniques on quartz. To further confirm the reliability of the chronology constructed based on OSL ages and test the applicability of the recently developed pIRIR procedure on sediments from northern China, twenty-four sediment samples (including eolian, lacustrine and fluvio-eolian sands) from the site were determined using the multi-elevated-temperature post-IR IRSL (MET-pIRIR or pIRIR) procedure on potassium feldspar. The results show that the studied samples have two MET-pIRIR De preheat plateaus (280–320 and 340–360 °C), and the bleaching rates of the luminescence signals are associated with sample ages and stimulation temperatures. All the pIRIR ages (7–155 ka) corrected for anomalous fading and residual dose obtained after solar bleaching for 15 h are larger than the corresponding quartz OSL ages (4–66 ka) previously determined, even for the young eolian samples (<10 ka). But the corrected IRSL(50 °C) ages (6–85 ka) are broadly consistent with the quartz ages. It appears that the IRSL(50 °C) ages are more reliable, although this contradicts the previously results obtained by other people. On the other hand, we also obtained an extended age plateau between the stimulation temperatures of 50 and 290 °C in the plot of age versus stimulation temperature (A-T plot) by subtracting different residual doses obtained after different bleaching times. The reliability of the plateau ages requires further investigation. For the sediment samples from this site, quartz should be more suitable for dating than K-feldspar, and the quartz OSL ages of 50–65 ka for its cultural layer should be reliable. 相似文献
30.
西藏甲玛铜多金属矿区成矿斑岩的岩浆混合作用:石英及长石斑晶新证据 总被引:6,自引:3,他引:3
西藏甲玛矿区斑岩内石英和长石斑晶的阴极发光(CL)特征及元素含量变化有效记录了岩浆演化、混合及补给事件.石英斑晶的显微生长结构表明,原始岩浆经历过2次铁镁质岩浆混合作用.根据石英斑晶中Ti含量的变化可知,在2次溶蚀前后,石英结晶温度分别增高了约110℃和80℃.此外,斜长石斑晶的反环带及其Ba、Sr、Fe等元素的浓度梯... 相似文献