首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 419 毫秒
1.
人发中铜,锌,铁,锰,钙,镁,钾,钠的测定   总被引：3，自引：1，他引：3  
  相似文献   

2.
以泥盆系占优势的南秦岭成矿带中存在有重要的Ｐｂ－Ｚｎ－Ａｇ，Ａｕ，Ｈｇ－Ｓｂ及Ｃｕ矿床。它们形成中晚古生带扬子地块北部被动大陆边缘的沉积盆地演化与造山期中，成矿系列显示出时间与空间的演化特征，构在了一个热水沉积成矿系列，成矿发生于一个热旋回中，各种矿化有相似的物源，每一种地质事件都有特定的金属富集及富集在型和大型矿床是该地区构造－岩浆变质变形作用的最终产物。  相似文献   

3.
原子吸收法测定茶叶中钙,镁,钾,钠,铁,锰,铷   总被引：6，自引：0，他引：6  
  相似文献   

4.
  相似文献   

5.
  相似文献   

6.
  相似文献   

7.
张海政  阎欣 《地质实验室》1996,12(6):330-332
应用ＩＣＰ－ＭＳ法测定了岩石中的痕量Ｎｂ、Ｔａ、Ｚｒ、Ｈｆ、Ｔｈ、Ｕ，给出了检出限，并对酸溶和碱熔两种制样方法进行了对比实验。  相似文献   

8.
The long controversy over the term ‘Quaternary‘ as a chronostratigraphic unit may be reaching an apotheosis, judging from recent papers (Pillans and Naish, 2004; Gibbard et al., 2005; and referencest herein). The debate is no longer centered on whether there should be a place in the geological time scale for a unit termed ‘Quaternary‘-despite its dubious past, it cannot be denied that a large body of earth-historical research is strongly identified with this term. The challenge now concerns an appropriate rank and definition of Quaternary with regard to other chronostratigraphic units. Several options have been proposed (Pillans and Naish, 2004), and Gibbard et al. (2005) encourage a debate on these before decision is reached. In this brief note, we describe an arrangement not previously considered that seems advantageous. It is instructive, however, to first review the Pleistocene Series and Neogene System, the two units that are directly affected by introduction of the Quaternary into the chronostratigraphic hierarchy.  相似文献   

9.
大陆漂移, 板块构造, 地质力学   总被引：2，自引：0，他引：2  
赵文津 《地球学报》2009,30(6):717-731
本文简要地介绍了魏格纳大陆漂移说的主要内容及其提出的依据; 论述了在大陆漂移说的基础上, 由于海洋地质地球物理调查发现了大洋中脊、洋底扩张, 解释了大陆张裂的机制, 并建立了全球板块构造理论, 形成现代地学思想的革命; 李四光在大陆漂移说提出的同时已在积极地探讨和论述大陆地壳水平运动问题, 并结合中国大陆实际, 发展了陆内碰撞变形理论, 即包括全球大陆构造体系在内的地质力学理论和方法。他强调地质力学是一支脚站在地质上, 另一支脚站在力学上来研究地壳运动和变形现象。后来更扩大了其在资源、环境方面的应用。文章对魏格纳大陆漂移说、全球板块构造理论及地质力学三者的关系做了深入探讨, 论述了李四光地质力学理论方法的现代意义、超前意义, 提出要重视和发扬李四光留给中国人民的宝贵遗产, 建议深入学习李四光的著述, 结合地质调查新成果去丰富它和发展它。  相似文献   

10.
We collected groundwaters in and around a large (313 Mt at 1.08% Cu and 0.3% cutoff) undisturbed porphyry copper deposit (Spence) in the hyperarid Atacama Desert of northern Chile, which is buried beneath 30–180 m of Miocene piedmont gravels. Groundwaters within and down-flow of the Spence deposit have elevated Se (up to 800 μg/l), Re (up to 31 μg/l), Mo (up to 475 μg/l) and As (up to 278 μg/l) concentrations compared to up-flow waters (interpreted to represent regional groundwater flow). In contrast, Cu is only elevated (up to 2036 μg/l) in groundwaters recovered from within the deposit; Cu concentrations are low down gradient of the deposit. The differential behavior of the metals/metalloids occurs because the former group dissolves as anions, enhancing their mobility, whereas the base metals dissolve as cations and are lost from solution most likely through adsorption to clay surface exchange sites and through formation of secondary copper chlorides, carbonates, and oxides. Most groundwaters within and down-flow of the deposit have Eh–pH values around the FeII/FeIII phase boundary, limiting the impact of Fe-oxyhydroxides on oxyanions mobility. Se, Re, Mo, and As are all mobile (with filtered/unfiltered samples ～ 1) to the limit of sampling 2 km down gradient from the deposit. The increase in ore-related metals, metalloids, and sulfate and decrease in sulfate–S isotope ratios (from values similar to regional salars, + 4 to + 8‰ δ34SCDT to lower values closer to hypogene sulfides, + 1 to + 4‰ δ34SCDT) is consistent with active water–rock reactions between saline groundwaters and the Spence deposit. It is likely that hypogene and/or supergene sulfides are being oxidized under the present groundwater conditions and mineral saturation calculations suggest that secondary copper minerals (antlerite, atacamite, malachite) may also be actively forming, suggesting that supergene and exotic copper mineralization is possible even under the present hyperarid climate of the Atacama Desert.  相似文献   

11.
The Cretaceous granites of Mianning, located in the northern Panxi region, were emplaced after collision of the Tibetan Plateau and Yangtze Block. These granites have very high K2O + Na2O, Ga, Zr, Nb, Y, REE (except Eu), and very low MgO, CaO, P2O5, and Sr contents relative to M-, I- or S-type granites. Based on the chemical discrimination criteria of Whalen et al . [Whalen, J.B., Currie, K.L., Chappell, B.W., 1987. A-type granites: geochemical characteristics, distribution and petrogenesis. Contributions to Mineralogy and Petrology 95, 407–419], most of them are A-type granites. Moreover, the granites plot in the range of post-collision granites and belong to the A2 type. Elevated initial Sr isotopic ratios (>0.72) suggest their derivation dominantly from a crustal source. These features are consistent with granite formation in a post-orogenic setting, such as after subduction or collision between of the Tibetan Plateau and Yangtze Block. In addition, the granites are characterized by low abundances of Ba, Sr, P, Ti, and Eu, positive correlation between Ba and Eu anomalies, and negative correlation between Rb and K/Rb. Plots of Rb vs. Sr suggest that fractional crystallization affected the final compositions of these granites after melting from a dominantly crustal source. From the late Proterozoic to late Mesozoic, the crustal composition, compared to that of the mantle, appears to have increased in the Panxi region. While the mantle component played an important part in the generation of Cretaceous granites in southeastern China, its influence was relatively minor in the Panxi region. Thus, there was a significant difference in mantle evolution between southeastern China and the Panxi region, which led to different metallogenic processes.  相似文献   

12.
This study presents the geochemical characteristics of granitic rocks located on the northern margin of Chotanagpur Gneissic Complex (CGC), exposed in parts of Gaya district, Bihar and discusses the possible petrogenetic process and source characteristics. These granites are associated with Barabar Anorthosite Complex and Neo-proterozoic Munger–Rajgir group of rocks. The granitic litho-units identified in the field are grey, pink and porphyritic granites. On the basis of geochemical and petrographic characteristics, the grey and pink granites were grouped together as GPG while the porphyritic granites were named as PG. Both GPG and PG are enriched in SiO2, K2O, Na2O, REE (except Eu), Rb, Ba, HFSE (Nb, Y, Zr), depleted in MgO, CaO, Sr and are characterised by high Fe* values, Ga/Al ratios and high Zr saturation temperatures (GPGavg～ 861 °C and PGavg～ 835 °C). The REE patterns for GPG are moderately fractionated with an average (La/Yb)N～ 4.55 and Eu/Eu* ～ 0.58, than PG which are strongly fractionated with an average (La/Yb)N～ 31.86 and Eu/Eu* ～ 0.75. These features indicate that the granites have an A-type character. On the basis of geochemical data, we conclude that the granites are probably derived from a predominant crustal source with variable mantle involvement in a post-collisional setting.  相似文献   

13.
A-type granites: geochemical characteristics,discrimination and petrogenesis   总被引：318，自引：3，他引：318  
New analyses of 131 samples of A-type (alkaline or anorogenic) granites substantiate previously recognized chemical features, namely high SiO2, Na2O+K2O, Fe/Mg, Ga/Al, Zr, Nb, Ga, Y and Ce, and low CaO and Sr. Good discrimination can be obtained between A-type granites and most orogenic granites (M-, I and S-types) on plots employing Ga/Al, various major element ratios and Y, Ce, Nb and Zr. These discrimination diagrams are thought to be relatively insensitive to moderate degrees of alteration. A-type granites generally do not exhibit evidence of being strongly differentiated, and within individual suites can show a transition from strongly alkaline varieties toward subalkaline compositions. Highly fractionated, felsic I- and S-type granites can have Ga/Al ratios and some major and trace element values which overlap those of typical A-type granites.A-type granites probably result mainly from partial melting of F and/or Cl enriched dry, granulitic residue remaining in the lower crust after extraction of an orogenic granite. Such melts are only moderately and locally modified by metasomatism or crystal fractionation. A-type melts occurred world-wide throughout geological time in a variety of tectonic settings and do not necessarily indicate an anorogenic or rifting environment.Geological Survey of Canada contribution no. 18886  相似文献   

14.
Early Ordovician A-type granites in the northeastern (NE) Songnen Block NE China were studied to better understand the geodynamic settings in this region. This research presents new zircon U–Pb ages and whole-rock geochemical data for the Early Ordovician granites in the NE Songnen Block. Zircon U–Pb dating indicates that the granite in the Cuibei, Hongxing, and Meixi areas in the NE Songnen Block formed in the Early Ordovician with ages of 471–479 Ma. The granites show geochemical characteristics of high SiO2 and K2O compositions and low FeOT, MgO, CaO, and P2O5 compositions. They belong to a high K calc-alkaline series and display a weak peraluminous feature with A/CNK values of 0.98–1.14. The rocks have a ∑REE composition of 249.98–423.94 ppm, and are enriched in LREE with (La/Yb)N values of 2.87–9.87, and display obvious Eu anomalies (δEu?=?0.01–0.29). Trace elements of the studied granites are characterized by enrichment in Rb, Th, U, Pb, Hf, and Sm, and depletion of Ba, Nb, Ta, and Sr. They display geochemical features of high Zr?+?Y?+?Nb?+?Ce values (324–795 ppm) and Ga/Al ratios consistent with A-type granites. Based on particular geochemical features, such as high Rb/Nb (7.98–24.19) and Y/Nb (1.07–3.43), the studied A-type granites can be further classified as an A2-type subgroup. This research indicates that the Early Ordovician A-type granites were formed by the partial melting of ancient crust in an extensional setting. Lower Sr/Y and (Ho/Yb)N ratios indicate that plagioclase and amphibole are residual in the source, and garnet is absent, implying that the magma was generated at low levels of pressure. By contrast, the contemporaneous granites in the SE Xing’an Block suggest a subduction-related tectonic setting, and its adakitic property indicates a thickened continental crust. We suggest that the Paleo-Asian Ocean plate between the Xing’an and Songnen blocks subducted northward during the Early Ordovician. Meanwhile, the NE Songnen Block was exposed to a passive continental margin tectonic setting.  相似文献   

15.
Petrochemical studies on acid plutonic (granite, microgranite) and volcanic (rhyolite, trachyte) rocks occurring in the Siner area of the Siwana Ring Complex, Malani Igneous Suite have been carried out. These rocks are characterized by high concentrations of SiO2, Na2O, K2O, Zr, Nb, Y and REE (except Eu) but low in MgO, Fe2O3(t), CaO, Cr, Ni, Sr; indicating their A-type affinity. Field studies in conjunction with the geochemical characteristic indicate that the magmatism in the Siner area is generally represented by peralkaline suite of rocks which are formed due to rift tectonics. It is also suggested that these acidic rocks could have been derived by low degree partial melting of crustal material. Characteristics of certain pathfinder elements such as Rb, Ba, Sr, K, Zr, Nb, REE and the ratios of K/Rb, Zr/Rb, Ba/Rb along with the multi elemental primitive mantle normalized spidergrams suggest that the Siner peralkaline granites and microgranites have the potential for rare metal and rare earth mineralizations.  相似文献   

16.
The intrusion of granitoids into the Eastern Sierras Pampeanas in the Early Carboniferous took place after a long period of mainly compressional deformation that included the Famatinian (Ordovician) and Achalian (Devonian) orogenies. These granitoids occur as small scattered plutons emplaced in a dominant extensional setting, within older metamorphic and igneous rocks, and many of them are arranged along a reactivated large shear zone. A set of 46 samples from different granitic rocks: Huaco granitic complex, San Blas pluton, and the La Chinchilla stock from the Sierra de Velasco, Zapata granitic complex from Sierra de Zapata, and the Los Árboles pluton from Sierra de Fiambalá, display high and restricted SiO2 contents between 69.2 and 76.4 wt.%. On both FeO/(FeO + MgO) vs. SiO2 and [(Na2O + K2O) ? CaO] vs. SiO2 plots the samples plot in the ferroan and alkaline-calcic to calco-alkaline fields (FeO/(FeO + MgO) = 0.88–1.0%;[(Na2O + K2O) ? CaO] = 6.3–8.3%), thus showing an A-type granitoid signature. The high concentrations for the High Field Strength Elements (HSFE), such as Y, Nb, Ga, Ta, U, Th, etc. and flat REE patterns showing significant negative Eu anomalies are also typical features of A-type granites. Our petrogenetic model supports progressive fractional crystallization with dominant fractionation of feldspar and a source mineral assemblage enriched in plagioclase. Biotites have distinctive compositions with high FeO/MgO ratios (7.8–61.5), F (360–5610 ppm), and Cl (120–1050 ppm). The FeO/MgO ratios together with the F and Cl content of igneous biotites seem to reflect the nature of their parental host magmas and may be useful in identifying A-type granitoids. The isotopic data (Rb–Sr and Sm–Nd) confirm that the A-type granites represent variable mixtures of asthenospheric mantle and continental crust and different mixtures lead to different subtypes of A-type granite (illustrating the lack of consensus about A-type magma origin). We conclude that prominent shear zones play an important role in providing suitable conduits for ascending asthenospheric material and heat influx in the crust, a hypothesis that is in accord with other recent work on A-type granites.  相似文献   

17.
The Nakora Ring Complex(NRC)(732 Ma) occurs as a part of Malani Igneous Suite(MIS) in the West-ern Rajasthan,India.This complex consists of three phases(volcanic,plutonic and dyke).Geochemically,the Na-kora granites are peralkaline,metaluminous and slightly peraluminous.They display geochemical characteristics of A-type granites and distinct variation trends with increasing silica content.The peralkaline granites show higher concentrations of SiO2,total alkalies,TiO2,MgO,Ni,Rb,Sr,Y,Zr,Th,U,La,Ce,Nd,Eu and Yb and lower concen-trations of Al2O3,total iron,Cu and Zn than metaluminous granites.AI content is ≥1 for peralkaline granites and <1 for peraluminous and metaluminous granites.Nakora peralkaline granites are plotted between 4 to 7 kb in pressure and are emplaced at greater depths(16-28 km and 480-840℃) as compared to metaluminous granites which indicate the high fluorine content in peralkaline granites.The primitive mantle normalized multi-element profiles suggest that Nakora granites(peralkaline,metaluminous and peraluminous) are characterized by low La,Sr and Eu and relatively less minima of Ba,Nb and Ti which suggests the aspects related to crustal origin for Nakora magma.The Nakora granites are characterized as A-type granites(Whalen et al.,1987) and correspond to the field of "Within Plate Gran-ite"(Pearce et al.,1984).Geochemical,field and petrological data suggest that Nakora granites are the product of partial melting of rocks similar to Banded Gneiss from Kolar Schist Belt of India.  相似文献   

18.
Peridotite and granite xenoliths, in the early stage of weathering, occur in the Nyos volcanic region (NW Cameroon). Geochemical data shows that peridotites are marked by high concentrations of MgO (42.30 wt.%, with SiO2/MgO ∼ 1), chromium (2100 ppm), nickel (2100 ppm) and cobalt (104 ppm), as well as by low lanthanide contents (ΣREE: 7.41 ppm). Granites display SiO2 contents (70–73 wt.%), and are mostly peraluminous (1.40 > A/CNK < 1.6). They are also characterized by low contents in chromium (<24 ppm), nickel (ranging from 6 to 15 ppm) and cobalt (ranging from 3 to 6 ppm). Granites possess high lanthanide contents (ΣREE varying between 248.00 and 463.00 ppm), particularly in light lanthanides (LREE/HREE ratios ranging from 21 to 32). The chondrite-normalized patterns of the studied xenoliths are characterized by: (i) LREE enrichments in both rock types; (ii) negative Eu anomalies ([Eu/Eu*] ranging from 0.45 to 0.64) and weak positive Ce anomalies ([Ce/Ce*] ranging from 1.06 to 1.46) in granites. The weathering process provokes a remobilization of several trace elements notably light lanthanides.The geochemical survey of Platinum-Group Elements (PGE) done in these rocks in the early stage of weathering shows that PGE contents are less than 7 ppb in the peridotites. The highly concentrated elements are ruthenium (6.26 ppb) and platinum (5.53 ppb). The total PGE content is 14.57 ppb. These concentrations normalized with respect to chondrites display a flat spectrum from iridium to platinum. PGE contents in the granites are below detection limit except for two samples (LNY01 and LNY02) whose platinum content is close to 0.23 ppb.  相似文献   

19.
Zircon and xenotime, from two mineralogically and chemically contrasting granite suites occurring in the Kru?né Hory/Erzgebirge Mts., display extended compositional variability with respect to abundances of Zr, Hf, REE, Y, P, Th, Ca, Al, Fe and As. According to their geochemical signatures, P-rich (S-type) and P-poor (A-type) granites could be distinguished here. Both granite suites display high Ga/Al ratios (>2.6) and according to FeOtot./(FeOtot. + MgO) ratio can be classified as ferrous granites. Consequently, the both ratios cannot be used for discrimination S- and A-type granites. Both minerals are characterized by a variety of complex zircon-xenotime textures. They are usually strong hydrated and enriched in F. Zircon from P-rich granites displays a significant enrichment in P (up 0.24 apfu P), whereas zircon from P-poor granites has lower P and higher Y (up to 0.15 apfu Y). The xenotime-type substitution is the most important mechanism of isomorphic substitution in zircon in both granite suites. Zircon from both granite suites is typically enriched in Hf, especially unaltered zircon from P-rich granites (up to 8.2 wt. % HfO2). However in altered zircons the Hf/Zr ratio is higher in the P-poor granites. The Hf-rich zircon from unaltered P-rich granite crystallised from low temperature granite melt, whereas altered zircons crystallised during post-magmatic hydrothermal alteration (greisenization). Xenotime from P-poor granites displays a considerable enrichment in HREE (up to 40 mol. % HREEPO4) compared to xenotime from P-rich granites (up to 20 mol. % HREEPO4). Xenotime compositions from P-rich granites are influenced by brabantite-type substitution, whereas for xenotime from P-poor granites the huttonite-type substitution is dominant. Unusual enrichments in HREE is significant for xenotime from P-poor granites, especially in Yb (up to 0.17 apfu Yb) and Dy (up to 0.11 apfu).  相似文献   

20.
Nature of the crust in Maine,USA: evidence from the Sebago batholith   总被引：7，自引：0，他引：7  
 Neodymium and lead isotope and elemental data are presented for the Sebago batholith (293±2 Ma), the largest exposed granite in New England. The batholith is lithologically homogeneous, yet internally heterogeneous with respect to rare earth elements (REE) and Nd isotopic composition. Two-mica granites in the southern/central portion of the batholith (group 1) are characterized by REE patterns with uniform shapes [CeN/YbN (chondrite normalized) = 9.4–19 and Eu/Eu* (Eu anomaly) = 0.27–0.42] and ɛ Nd(t) = −3.1 to −2.1. Peripheral two-mica granites (group 2), spatially associated with stromatic and schlieric migmatites, have a wider range of total REE contents and patterns with variable shapes (CeN/YbN = 6.1–67, Eu/Eu* = 0.20–0.46) and ɛ Nd(t) = −5.6 to −2.8. The heterogeneous REE character of the group 2 granites records the effects of magmatic differentiation that involved monazite. Coarse-grained leucogranites and aplites have kinked REE patterns and low total REE, but have Nd isotope systematics similar to group 2 granites with ɛ Nd(t) = −5.5 to −4.7. Rare biotite granites have steep REE patterns (CeN/YbN = 51–61, Eu/Eu* = 0.32–0.84) and ɛ Nd(t) = −4.6 to −3.8. The two-mica granites have a restricted range in initial Pb isotopic composition (206Pb/204Pb = 18.41–18.75; 207Pb/204Pb = 15.60–15.68; 208Pb/204Pb = 38.21–38.55), requiring and old, high U/Pb (but not Th/U) source component. The Nd isotope data are consistent with magma derivation from two sources: Avalon-like crust (ɛ Nd>−3), and Central Maine Belt metasedimentary rocks (ɛ Nd<−4), without material input from the mantle. The variations in isotope systematics and REE patterns are inconsistent with models of disequilibrium melting which involved monazite. Received: 8 December 1995 / Accepted: 29 April 1996  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号