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2.
Application of radionuclide energy-dispersive x-ray fluorescence analysis in geochemical prospecting
A mobile radionuclide energy-dispersive X-ray fluorescence has been tested for its applicability as a field method for analysis of stream sediments and soil samples in geochemical prospecting. An instrument mounted in a four-wheel drive truck is described. Extensive investigations of interferences and their elemination were carried out. The method and system have been successfully tested for the elements Cu, Zn, As, Rb, Sr, Zr, Nb, Sn, Cs, Ba, La, Ce and Pb. 相似文献
3.
《International Geology Review》2012,54(9):1330-1338
Both the biotitic and the biotite-pyroxenitic nepheline syenites in the area are chemically intermediate between the agpaitic and the miaskitic types. They are characteristically high in calcium and are much higher in potassium than in sodium. Their Sn, Pb, Zn, Ni, Co, Cr, V, Cu, Ce, La, Nd are about the same as ingranitoids; Sr, Ba, Mo, Rb are much higher; their Li, Y, Te are much lower than the granitoid clarkes. —V.P. Sokoloff. 相似文献
4.
Trace element characteristics of graywackes and tectonic setting discrimination of sedimentary basins 总被引：79，自引：0，他引：79
The graywackes of Paleozoic turbidite sequences of eastern Australia show a large variation in their trace element characteristics, which reflect distinct provenance types and tectonic settings for various suites. The tectonic settings recognised are oceanic island arc, continental island arc, active continental margin, and passive margins. Immobile trace elements, e.g. La, Ce, Nd, Th, Zr, Nb, Y, Sc and Co are very useful in tectonic setting discrimination. In general, there is a systematic increase in light rare earth elements (La, Ce, Nd), Th, Nb and the Ba/Sr, Rb/Sr, La/Y and Ni/Co ratios and a decrease in V, Sc and the Ba/Rb, K/Th and K/U ratios in graywackes from oceanic island arc to continental island arc to active continental margin to passive margin settings. On the basis of graywacke geochemistry, the optimum discrimination of the tectonic settings of sedimentary basins is achieved by La-Th, La-Th-Sc, Ti/Zr-La/Sc, La/Y-Sc/Cr, Th-Sc-Zr/10 and Th-Co-Zr/10 plots. The analysed oceanic island arc graywackes are characterised by extremely low abundances of La, Th, U, Zr, Nb; low Th/U and high La/Sc, La/Th, Ti/Zr, Zr/Th ratios. The studied graywackes of the continental island arc type setting are characterised by increased abundances of La, Th, U, Zr and Nb, and can be identified by the La-Th-Sc and La/Sc versus Ti/Zr plots. Active continental margin and passive margin graywackes are discriminated by the Th-Sc-Zr/10 and Th-Co-Zr/10 plots and associated parameters (e.g. Th/Zr, Th/Sc). The most important characteristic of the analysed passive margin type graywackes is the increased abundance of Zr, high Zr/Th and lower Ba, Rb, Sr and Ti/Zr ratio compared to the active continental margin graywackes. 相似文献
5.
海南岛中元古代花岗岩地球化学及成因研究 总被引：16，自引：3，他引：16
海南岛中元古代花岗岩岩体主要由二长花岗岩、花岗冈长岩等岩石组成，构成一个明显的 自花岗岩向花岗闪长岩和英云闪长岩的岩浆演化系列及钙碱性演化趋势。该岩体为一套板块碰撞 后隆起期原地一半原地过铝质花岗岩。是板块碰撞引起的地壳增厚升温和随之的玄武岩浆底侵加 热联合作用下，主要由抱板群变质沉积岩及斜长角闪片麻岩部分融熔、并在幔源物质的参与下形 成的，所形成的花岗质岩浆在“走滑扩容泵吸”机制驱动下沿戈枕剪切带上升、固结就位，因而具壳 幔二元混合成因特点。化学成分以高 ＳｉＯ２、Ｋ２Ｏ、Ｒｂ、Ｂａ、Ｔａ、Ｃｅ和贫Ｐ、Ｔｉ、Ｚｒ、Ｓｒ、Ｆｅ２Ｏ３＋ＦｅＯ、 ＭｇＯ、ＣａＯ为特征；元素比值Ｚｒ／Ｎｂ、Ｌａ／Ｎｂ、Ｂａ／Ｎｂ、Ｒｂ／Ｎｂ、Ｋ／Ｎｂ、Ｂａ／Ｌａ及Ｃｒ、Ｃｏ、Ｎｉ、Ｖ均接近 大陆中下地壳成分，Ｒｂ、Ｓｒ、Ｂａ、Ｔａ、Ｚｒ及比值Ｋ／Ｓｒ、Ｒｂ／Ｓｒ石ｒ／Ｂａ变化范围小，反映岩浆源区成分 或熔融方式上的一致性；轻重稀土较强分馏，负铕异常明显，稀土配分模式总体相似，呈左高右低 型，和抱板群变质沉积岩稀上元素组成基本一致；εＮｄ（ｔ）值普遍高于抱板群地层，（８７Ｓｒ／８６Ｓｒ）ｉ值变化 大，暗示幔源参与信息。结合抱板群变基性火山岩的 相似文献
6.
The Shonkin Sag differentiation sequence displays systematic variations in major and trace elements with evolution. The accumulative more mafic shonkinites are enriched in Co, Ni, Cr; La, Ce, Zr, and Nb are concentrated in the most evolved differentiate, chemically a nepheline syenite. Maximum abundances of K, Rb, Ba, Pb, and Sr occur in the intermediate syenitic differentiates (differentiation index=64.0–68.8). A change in the variation trends for K, Rb, Pb, Sr, Na, Ce, and Zr coincided with a change in the rate of decrease of oxygen fugacity with falling temperature. 相似文献
7.
Bi-Shia Wang KING 《Geostandards and Geoanalytical Research》1987,11(2):193-195
Concentrations of twelve trace elements (Cr, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, La and Ce) in eight Chinese stream-sediment reference samples have been determined by energy-dispersive X-ray fluorescence spectrometry. The samples were analyzed directly and non-destructively in loose powder form. Compton scatter radiation was used as an internal standard to compensate for variations in sample matrix, particle size, packing density, and instrumental operating characteristics. The results agree well with the Chinese recommended values. 相似文献
8.
Based on 225 analyses of quartzites, siliceous granoblastites,calc silicate rocks, calcite and dolomite marbles, including120 analyses of pelites and semipelites, sedimentary trendsof chemical variation are identified in staurolite and sillimanitegrade rocks. The correlation of original clay mineral contentwith Ti, Fe, K, Rb, Y, Nb, Ca, Ni, Ga, Zn and probably Ba andMn is shown. A similar clay mineral (whose composition is calculated)was added to all the sediments except the quartz-rich sandstones,now quartzites. This pattern appears to be general for mostsediments, based on crustal averages. The form of the originaladdition of Sr in the sediments might be identified as eithercarbonate or feldspar by a Ca vs. Sr plot. The southern pelites in a 2–4 km peripheral zone to theConnemara orthogneisses and migmatites have been metasomatized.The crude order of elemental enrichment from the elements increasedthe most to those increased the least relative to the same stratigraphicalhorizons in the north is: Mn, Ba, Th, Cu, Ca, Sr, Y, Pb, Zn,Pr, Ge, Nd, La, Mg, S, Ce, Rb, Sm, Ti, Na, K and Ga while Si,Al, Cr, Ni, Co, Fe and P are unchanged or removed. The sourceof the material added is postulated to be the water-rich residualfraction of the migmatitic quartz diorite gneiss, the transportbeing by movement of a water-rich fluid out of the migmatites,the fixation being mainly in biotite and new, more calcic, plagioclaseporphyroblasts, there being a positive correlation between elementenrichment and ionic radius. 相似文献
9.
Carbonatites found in the Dara-i-Pioz alkaline massif, Tajikistan, form linearly-elongated, steeply-dipping and, sometimes,
rounded in plan pipe-like bodies of mainly calcitic composition. As compared to reference carbonatites, they have lower contents
of Fe, Mg, Ti, Sr, Ba, Mn, P, REE, Zr, Nb, Ta, and other elements but elevated contents of Rb, Cs, Al, Si, Na, K, and others.
However, the Dara-i-Pioz carbonatites are characterized by such typomorphic features of carbonatites as the sharp predominance
of LREE over HREE and high ΣCe: ΣY, La: Yb, and Sr: Ba ratios. 相似文献
10.
N. C. N. Stephenson 《Australian Journal of Earth Sciences》2013,60(1):83-94
Proterozoic basement outcrops in the vicinity of Battye Glacier, northern Prince Charles Mountains, are dominated by granulites and gneisses derived from felsic (granitoid) intrusive igneous rocks, and by pegmatites. Felsic orthopyroxene granulites, garnet leucogneisses and garnet pegmatites have major and trace element compositions of highly felsic, but not strongly fractionated, granites. The garnet leucogneisses and garnet pegmatites have S‐type characteristics, whereas the felsic granulites are probably I‐type, although their high Zr+Nb+Y+Ce abundances suggest possible A‐type affinities. Intermediate orthopyroxene ± clinopyroxene granulites mostly resemble I‐type quartz diorites, except for a small subgroup of samples (characterised by low Na2O and K2O, and high MgO, Ni, Cr and HREE) of uncertain affinities and significance. Element ratios involving LILE (e.g. K/Rb, Rb/Ba, Rb/Sr, K/La, La/Th) closely match those typical of the inferred granitoid protoliths, suggesting that these rocks have experienced relatively little LILE depletion (except possibly for U) during regional metamorphism. It is therefore inferred that metamorphism was probably broadly isochemical. Because the felsic and intermediate granulites and garnet leucogneisses are Sr‐depleted, Y‐undepleted and mostly have negative Eu anomalies they are inferred to be the products of partial melting of felsic crustal sources leaving plagioclase‐bearing residua. Plagioclase fractionation during crystallisation could also account for these characteristics, but K/Rb, Rb/Ba and Rb/Sr ratios in these rocks are not consistent with strong fractionation of feldspar. Garnet pegmatites differ chemically from garnet leucogneisses mainly in their lower Fe, Ti, Nb, Zn, Zr, Th and REE abundances and positive Eu anomalies, related to lower garnet, ilmenite and zircon contents in the garnet pegmatites. A genetic link between these two rock types, probably involving fractionation of these minerals during partial melting or crystallisation, is inferred. Incompatible‐element abundances suggest that generation of the Battye Glacier granitic magmas from felsic crust might have occurred in a mature continental magmatic arc possibly well removed from an active subduction trench or, perhaps, in an intracontinental setting. 相似文献
11.
《International Journal of Coal Geology》2005,61(1-2):87-95
The concentration of trace elements and their distribution in the late Permian coal in the Heshan coal field, Guangxi Autonomous Region, were analysed in this paper. The late Permian coal of the Heshan mining district was developed in a low energy and shallow, confined carbonate platform. Heshan coal is a low volatile bituminous coal characterized by a high sulphur content, ranging between 2.0% and 8.2%. Compared with the worldwide average content of the trace elements in coal, the content of some trace element in the study coal is markedly high (Bi, Ce, Cr, Cs, Cu, Ga, Hf, Sr, Ta, Th, U, V, W, Y, Zr, La, Mo, Nb and Sc).The trace element associations were investigated by means of intracorrelation analysis. Some elements, such as Cl, F and Sr are found in coal in association with the carbonate minerals. V, Cr, Zn, Mo, Ni and As contents in coal vary significantly amongst the coal samples. They are mainly concentrated in the lower part of the coal #4 upper of Suhe and Lilan mines and the coal #4 lower of Dong mine, and these possibly occurring in minerals such as arsenide and sulphide. The content of U in Heshan coal is high and is mainly concentrated at the upper and the lower parts of the coal seam and it is associated with mineral assemblages with Ba, Mo, V, Ni, Zn, Rb and Cr. Furthermore, La and Ce are highly correlated with those found in phosphate minerals and Pb, Sc, Ga, Th, Y and Sn to those in aluminosilicate minerals. The enrichment of some elements such as V, Cr, Zn, Mo, Ni, Rb as well as total sulphur and iron in the lower part of most coal seams might be associated with the formation of soil horizon before the accumulation of peat in the basin. Some other elements such as Cl, F, Sr and Ca are locally concentrated in the top of specific coal seams as a result of the leaching from overlying carbonates. 相似文献
12.
An area of 324 km2 was selected for a pilot-study of the geochemical characteristics of the Bushveld granites in the Potgietersrus tin-field. Two hundred and sixty nine samples were collected from a regular grid of stations. Additional samples collected from selected sample stations provide data on “about station” variance to test the validity of conclusions based on regional variation. The samples were analysed for Ba, Ce, Co, La, Li, Nb, Ni, Rb, Sc, Sn, Sr, Ti, Y, Zn and Zr together with the major elements Ca, Na and K.The stratiform Bushveld granites have mean concentrations for these elements that compare closely with those in low Ca-granites. Ce, La, Rb, Y, Zn and Zr are enriched relative to low Ca-granites while Sr is markedly impoverished. The stanniferous Bobbejaankop granite stock is distinguished from the stratiform granites with respect to Ba, Sr, Ti and Zn. The median tin concentration in the stratiform granites is 6.5 ppm and in the Bobbejaankop granite it is 9 ppm. Economically viable deposits of tin disseminated through the upper 120 m of the Bobbejaankop granite stock have been exploited for over 70 years.It is concluded that the Bobbejaankop granite crystallized at low temperatures from a hydrous residual melt that had collected beneath a roof of felsite and early crystallization products of the original granitic magma. The presence of this concentration of volatile-rich, hydrous liquid depressed the melting temperatures of the quasi-solid, granitic crystal much below the ambient temperature initiating re-mobilization. The enrichment in Sn of the stratiform granites in the Potgietersrus area is compared with the “normal” (i.e., ± 3 ppm) Sn-content of the Bushveld stratiform granites building the Sekukuni Plateau in the eastern lobe of the Bushveld Complex where no tin mineralization has been reported. 相似文献
13.
M.F.J. Flower 《Chemical Geology》1973,12(2):81-98
The elements Cr, Ni, Cu, Zn, Rb, Sr, Y, Zr and Ba have been determined by X-ray fluorescence for 65 basaltic and differentiated lavas from Anjouan, while Sc, V, Cr, Co, Ni, Cu, Ga, Rb, Sr, Y, Zr, Nb, Cs, Ba and Hf have been determined by spark-source mass spectrometry for selected lavas from Anjouan and Grande Comore, the most recently formed of the Comores Archipelago. Basaltic lavas studied range through nephelinite, basanite, alkali basalt and hypersthene-normative basalt, while differentiated lavas belong mainly to the trends: alkali basalt - trachyte and basanite - phonolite. The results indicate that during magmatic fractionation behaviour of large-ion elements such as Rb, Sr, Y, Zr, Ba and Nb is controlled by size/charge criteria, resulting in their exclusion from crystallising phases until the late trachytic and phonolitic stages. These elements are clearly fractionated by amphibole, plagioclase and alkali feldspar. Variation of transition elements due to crystal-liquid differentiation is largely in accord with the predictions of crystal field theory. The behaviour of Zn is not readily accounted for. Fractionation of K/Rb, K/Cs and probably Zr/Nb and discrepancies in abundance levels of large-ion elements between the main basaltic types are best accounted for in terms of high-pressure processes and probably also reflect inherent features of source-region geochemistry, coupled with the effects of variable partial melting. 相似文献
14.
Chemistry of Aerosols over Chukchi Sea and Bering Sea 总被引：2，自引：0，他引：2
The contents of elements in aerosols sampled during the First Chinese Arctic Research Expedition (CHINARE-1) show great differences from one element to another. Na, K,Ca, Mg, A1, F, and Cl are the major components in the aerosols, whose contents are larger than 30 ng/m^3. The chemical elements whose contents vary between 0.1 - 30 ng/m^3 are Br,Sr, Cr, Ni, and Zn. The chemical elements whose contents are close to or slightly higher than 0.1 ng/m^3 are Rb, Ba, Zr, Th, and Pb. The contents of As, Sb, W, Mo, Au, La, Ce, Nd,Sin, Eu, Tb, Yb, Lu, Sc, Co, Hf, Ta, and Cd are less than 0.1 ng/m^3. The mass concentration data for the same element, as observed during CHINARE-1, are almost accordant, but much lower than what is observed in the China‘ s seas or the coasts of China. The enrichment factor and electron microscopic analyses and lead isotope tracing were used to distinguish their sources.Four groups of sources can be classified as follows: anthropogenic: As, Sb, W, F, Mo, Au,Cu, Pb, Cd, V; crustal: La, Ce, Nd, Sm, Eu, Tb, Yb, Lu, Fe, Sc, Cr, Co, Ba, Zr, Hf,Ta, Cs, Mn, Th, U; oceanic:Na, K, Ca, and Mg; and mixing: Rb, Sr, Ca, and Mg. 相似文献
15.
A.E. Kelepertsis 《地学学报》1993,5(1):52-60
The mobilities of major and trace elements have been investigated in hydrothermally altered volcanic rocks of Pliocene age on the island of Lesvos. One type of hydrothermal assemblage, montmorillonite-K-feldspar-goethite, was recognized in outcrops north of Mytilini town. The alteration occurs a few metres under the surface of unaltered volcanic rocks of high-K andesite and high-K basaltic andesite composition. The unaltered latite-andesite consists of plagioclase, clinopyroxene, sanidine and magnetite with quartz, calcite, pumpellyite and montmorillonite as subordinate secondary minerals. The main control over major oxide distribution appears to be the extent of conversion of plagioclase to K-feldspar. Three distinct groups of elements were revealed to be positively correlated:
- 1 Si, Mg, Ca, Na, Mn, Sr and Ba, which are leached during the alteration process. This group of elements reflects their association with plagioclase feldspar and clinopyroxene.
- 2 Fe, K, Ti, P, Nb, Zr, Y, Rb, Ni, Cr, V. This group includes elements which are enriched relative to the unaltered volcanic rock, reflecting their association with K-feldspar, iron hydroxides and Ti and P-bearing minerals.
- 3 Ti, P, Nd, La, Ce. From this group of elements it is indicated that Nd, La and Ce are associated with Ti- and P-bearing minerals.
16.
骆驼山镁铁--超镁铁岩体主要岩石类型有单辉橄长岩、橄榄辉长苏长岩、橄长岩、辉长苏长岩、辉长岩。橄榄石Fo为76~83,为贵橄榄石。辉石化学特征以及主量元素特征表明其属拉斑玄武岩系列,稀土元素配分曲线总体表现为轻稀土稍富集、重稀土微分异的特征。微量元素具有大离子亲石元素(Rb、Ba、Sr)相对富集,高场强元素Ta、Hf、Th相对亏损的特征。岩浆演化过程中分离结晶作用主要受单斜辉石控制。Nb/U、Ce/Pb值更接近于地壳值以及敏感元素比值协变关系表明岩浆演化过程发生了同化混染作用。Th/Yb-Nb/Yb、La/Ba-La/Nb之间的关系指示岩浆源区可能为流体交代改造的富集型岩石圈地幔。 相似文献
17.
东南沿海分布大面积的白垩纪晚期侵入岩。这些岩石可分为两期:其中115~100Ma以钙碱性系列岩石为主,岩石组合为辉长岩-闪长岩-花岗闪长岩-二长花岗岩-碱性长石花岗岩;而100~86Ma的岩石为碱性系列,岩石组合为石英二长斑岩-正长斑岩-碱性长石花岗岩。115~100Ma的辉长岩以角闪辉长岩为主,具有极高的CaO、MgO和Al_(2)O_(3)含量,具有极低的SiO_(2)(42.9%~53.8%)、全碱(K_(2)O+Na_(2)O:0.86%~5.28%)、Ba、Nb、Th、Rb和Zr含量,也具有极低的FeO^(T)/MgO、La/Yb和Zr/Hf比值,较高的Eu/Eu^(*)、Sr/Y比值和Sr含量,为基性-超基性堆晶岩。与辉长岩同期的闪长岩和细粒暗色包体具有较高的SiO_(2)(50.34%~63.68%),较低的CaO、P_(2)O_(5)、MgO、Al_(2)O_(3)含量,相对低的Eu/Eu^(*)和Sr/Y比值,变化较大的La/Yb和Zr/Hf比值,代表了从基性岩浆储库中抽取的富硅熔体。115~100Ma的花岗闪长岩和二长花岗岩类岩石为准铝质岩石,SiO_(2)含量变化较大(61.7%~75.3%),具有较低的FeO^(T)/MgO、Ga/Al比值和Nb、Zr及Nb+Zr+Ce+Y元素含量,显示出典型I型花岗岩的特征。这些花岗岩具有相对高的La/Yb、Eu/Eu^(*)和Zr/Hf比值和高的Sr、Ba和Zr含量。结合岩相学特征,这些花岗岩为堆晶花岗岩。而115~100Ma的碱性长石花岗岩具有极高的SiO_(2)含量(大于75%),低的Eu/Eu^(*)、La/Yb、Zr/Hf和Sr/Y比值,具有低的Ba、Sr和Zr含量和高的Rb、Nb、Y和Th含量和Rb/Sr比值,表明这些花岗岩是由富硅岩浆储库中抽离的高硅熔体侵入地壳形成。100~86Ma期间形成的二长斑岩和正长斑岩具有极高的全碱含量,可以达到8%~12%,其SiO_(2)主要集中在60%~70%,具有极高的Zr、Sr和Ba含量和Eu/Eu^(*)、La/Yb和Sr/Y比值,显示出堆晶花岗岩的特征。而100~86Ma期间形成的大部分碱性长石花岗岩具有极高的SiO_(2)含量(大于75%),并显示出A型花岗岩的特征,具有高的Rb/Sr比值和高的Rb、Y和Th和低的Ba、Sr含量和低的Zr/Hf、La/Yb、Eu/Eu^(*)和Sr/Y比值,表明它们是由富硅岩浆储库抽离的高硅熔体侵入浅部地壳形成。东南沿海高硅花岗岩的形成和穿地壳岩浆系统密切相关,高硅花岗岩是由浅部地壳内晶体-熔体分异产生的熔体侵入地壳所形成,而高硅花岗岩的地球化学特征与岩浆储库的水及挥发份含量密切相关。115~100Ma期间,从富水的岩浆储库抽离的熔体形成具有低高场强元素含量和低Rb/Sr比值的高硅花岗岩,这一过程与古太平洋板块俯冲有关;100~86Ma期间,从富挥发份的岩浆储库抽离的熔体形成碱性特征、富含高场强元素和具有高的Rb/Sr比值的高硅花岗岩,这一过程和古太平洋板块回撤软流圈上涌有关。 相似文献
18.
Raimundo Jiménez Ballesta Paz Conde Bueno Juan A. Martin Rubi Rosario Garcia Giménez 《Central European Journal of Geosciences》2010,2(4):441-454
To evaluate trace element soil contamination, geochemical baseline contents and reference values need to be established. Pedo-geochemical baseline levels of trace elements in 72 soil samples of 24 soil profiles from the Mediterranean, Castilla La Mancha, are assessed and soil quality reference values are calculated. Reference value contents (in mg kg?1) were: Sc 50.8; V 123.2; Cr 113.4; Co 20.8; Ni 42.6; Cu 27.0; Zn 86.5; Ga 26.7; Ge 1.3; As 16.7; Se 1.4; Br 20.1; Rb 234.7; Sr 1868.4; Y 38.3; Zr 413.1; Nb 18.7; Mo 2.0; Ag 7.8; Cd 4.4; Sn 8.7; Sb 5.7; I 25.4; Cs 14.2; Ba 1049.3; La 348.4; Ce 97.9; Nd 40.1; Sm 10.7; Yb 4.2; Hf 10.0; Ta 4.0; W 5.5; Tl 2.3; Pb 44.2; Bi 2.2; Th 21.6; U 10.3. The contents obtained for some elements are below or close to the detection limit: Co, Ge, Se, Mo, Ag, Cd, Sb, Yb, Hf, Ta, W, Tl and Bi. The element content ranges (the maximum value minus the minimum value) are: Sc 55.0, V 196.0, Cr 346.0, Co 64.4, Ni 188.7, Cu 49.5, Zn 102.3, Ga 28.7, Ge 1.5, As 26.4, Se 0.9, Br 33.0 Rb 432.7, Sr 3372.6, Y 39.8, Zr 523.2, Nb 59.7, Mo 3.9, Ag 10.1, Cd 1.8, Sn 75.2, Sb 9.9, I 68.0, Cs 17.6, Ba 1394.9, La 51.3, Ce 93.5, Nd 52.5, Sm 11.2, Yb 4.2, Hf 11.3, Ta 6.3, W 5.2, Tl 2.1, Pb 96.4, Bi 3.0, Th 24.4, U 16.4 (in mg kg?1). The spatial distribution of the elements was affected mainly by the nature of the bedrock and by pedological processes. The upper limit of expected background variation for each trace element in the soil is documented, as is its range as a criterion for evaluating which sites may require decontamination. 相似文献
19.
Characteristics of geochemical evolution of trace elements and REE in Gejiu granites,Yunnan Province
Jie Lu 《中国地球化学学报》1988,7(2):155-169
The evolution characteristics of Gejiu granites, Yunnan Province are described in terms of their petrology, especially their
trace elements and REE geochemistry. The three major types of Gejiu granites: porphyritic biotite monzonitic granite (stage
I), medium-coarse-grained biotite-K-feldspar granite (stage II) and two-mica alkali-feldspar granite (stage III) are thought
to have been formed successively from the same granite magma source through fractional crystallization (Rayliegh fractionation),
because linear correlations are found between log(Rb/Sr)-log Sn, log(Rb/Ba)-log Sn, log(Rb/Ba)-log(Rb/Sr), log La-log Sr,
log Ce-log Sr, log Eu-log Sr, etc. In addition, the characteristics of REE distribution patterns in these three major types
of granites also reflect the magmatic differentiation features of Gejiu granites. Of the three major types, the two-mica alkali-feldspar
granite of stage III underwent the strongest differentiation, and thus has the closest genetic relationship with the Gejiu
tin-polymetallic ore deposit. Such tin-polymetal mineralized granites are characterized by high Rb/Sr and Rb/Ba ratios, low
K/Rb and ΣCe/ΣY ratios and remarkable Eu depletion. 相似文献
20.
Geology,geochemistry and petrogenesis of late Precambrian granitoids in the Central Hijaz Region of the Arabian Shield 总被引：1，自引：0，他引：1
Late Precambrian granitoid rocks occurring within a 44,000 km2 area of the western Arabian Shield are subdivided on the basis of geology and petrology into older (820 to 715 Ma) and younger (686 to 517 Ma) assemblages. The older assemblage contains major complexes which can be assigned to either one of a granodioritic or trondhjemitic petrologic association. The earliest granitoid rocks are trondhjemitic tonalites (trondhjemite association), depleted in Ba, Ce, F, La, Li, Nb, Rb, Y and Zr compared to granitoids of the slightly younger granodiorite association, which are related to a calcic, calc-alkaline suite of rocks ranging in composition from gabbro through monzogranite. The plutonic rocks of the older assemblage were probably emplaced in the cores of contemporary island arcs.The younger plutonic assemblage is dominated by three, geochemically distinct, coeval granitic associations: the alkali granite, alkali-feldspar granite and monzogranite associations. The alkali granite association is composed of perthite granites (alkali granites and genetically related alkali-feldspar granites). Rocks of this association are marginally peralkaline or metaluminous and are characterized by low contents of Ba, Co, Li, Rb, Sc and Sr, and high contents of Be, Cu, F, REE, Nb, Sn, Y, Zn and Zr. The alkali-feldspar granite association is mainly composed of alkali-feldspar granites and syenogranites. Rocks of this association are marginally peraluminous or metaluminous and contain low Ba, Sr, and high F, Rb, Sn, Th and U. The monzogranite association consists mainly of monzogranites and granodiorites. Rocks of this association are peraluminous or marginally metaluminous and have the highest contents of Ba, Cu, Co, Li, Sc, Sr, Ta, and V, and the lowest contents of REE, Nb, Rb, Sn, Th, U, Y, Zn and Zr of the three granitic associations.These voluminous granitic magmas, together with the felsic component of a coeval sequence of bimodal volcanic rocks, are partial melts of the earlier island arc terrain produce during a prolonged fusion event. Subsolvus, highca granites of the monzogranite association have I-type features and represent partial melts of previously unfused crust, while low-Ca perthite granites of the alkali granite and alkali-feldspar granite associations have A-type features and represent partial melts of previously fused crust.This type of petrogenetic model can account for much of the petrologic diversity of the Pan-African granitic terrain of the Arabian Shield. 相似文献