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1.
Kimberlite magmas from the Kimberley area of South Africa have sampled two main types of phlogopite-rich mafic xenoliths which represent deep mantle segregations from highly alkaline melts. The first group corresponds to the MARID rocks characterised by the mineral association mica (phlogopite)-amphibole (K-richterite)-rutile-ilmenite-clinopyroxene and the second group consists of the PIC rocks characterised by the mineral association mica (phlogopite)-ilmenite-clinopyroxene-minor rutile. The two groups are clearly distinguished from one another by their mineral paragenesis, by the major element composition of their phlogopite and ilmenite, by the trace element content of their clinopyroxene and by their clinopyroxene and whole rock Sr and Nd isotope ratios. The combined major and trace element variations are interpreted to indicate a genetic relationship between the PIC rocks and group I kimberlite magma, and between the MARID rocks and group II kimberlite magma. The two types of parental melts percolated through, and metasomatised, the upper mantle beneath the Kimberley area as indicated by the trace element characteristics of the clinopyroxenes of the studied phlogopite-bearing peridotites. 相似文献
2.
湖南水口山铅锌金银矿床地球化学特征 总被引：1，自引：0，他引：1
根据湘南区域地球化学特征,结合水口山矿区地质矿床特征,分别从地层、岩性,构造类型及热岩系的微量元素地球化学特征,对两大不同成岩、成矿系列中不同微量元素组合可引起的原、次生晕异常特征作了较为深入研究、讨论。 相似文献
3.
The origin of anorthosite and associated igneous gabbronorite and ferrodiorite was investigated through detailed study of
a typical massif-type anorthosite complex from Gruber, Central Dronning Maud Land, East Antarctica. Field observations showed
that the Gruber Complex is made up of gabbronorite-anorthosite pluton which was intruded by ferrodiorite dykes. Systematic
samples collected from the Gruber Complex revealed significant geochemical variations within the region. Four rock types have
been identified, based on modal proportions of mineral phases and their geochemistry data. Clinopyroxene-gabbronorite and
plagioclase-gabbronorite are the two types of gabbronorite with the dominance of clinopyroxene and plagioclase, respectively.
Anorthosite is represented by rocks having predominance of plagioclase with minor clinopyroxene. Ferrodiorite is characterized
by modal abundance of orthopyroxene and Fe-Ti oxide. Major and trace element systematics showed that all the four rock types
are co-magmatic and are related through fractional crystallization. Based on this study, it is reported that clinopyroxene
was the first phase to crystallize followed by plagioclase and then Fe-Ti oxides. Furthermore, trace element composition of
the parental melt was calculated using LA-ICPMS analysis of the most primitive, pure clinopyroxene found in the clinopyroxene
gabbronorite. Our analyses suggested that the parental melt was similar to that of continental arc basalt and showed signatures
of subduction-related metasomatism. Based on mineral chemical and geochemical data, it is interpreted that the parent melt
went through changing sequence of crystallization which led to the formation of massive anorthosite. 相似文献
4.
Petrogenesis of Group I Kimberlites from Kimberley, South Africa: Evidence from Bulk-rock Geochemistry 总被引：8，自引：6，他引：8
Fresh samples of hypabyssal kimberlite from the five major kimberlitepipes in the Kimberley area of South Africa have been analysedfor their bulk-rock major and trace element geochemistry. Thegeochemical data allow identification of the influence of crustalcontamination in certain samples, best illustrated in termsof elevated SiO2, Al2O3, Pb and heavy rare earth element (HREE)contents. Samples devoid of such crustal contamination showcoherent major and fluid-immobile trace element variations,whereas fluid-mobile trace elements are scattered. Kimberlitesrich in macrocrysts are shown to reflect substantial (up to35%) entrainment of mantle peridotite, with Ni–SiO2 andSc–SiO2 variations defining mixing trajectories towardsgarnet lherzolite. The likely primary magma(s) parental to theKimberley kimberlites is suggested to have a composition of26–27 wt % MgO, 26–27 wt % SiO2, 相似文献
5.
用质子探针和电子探针分别测定盘石山幔源橄揽岩包体中透辉石、橄榄石的微量元素和主量元素丰度;用X-射线荧光光谱法测定包体全岩的主量和微量元素丰度。定量讨论微量元素的分布和分配。其中绝大部分Sr、Zr、Ti、Na赋存在透辉石中,绝大部分Mn、Zn、Ni赋存在橄揽石中,在T=1194-1435K范围,分配系数变化如下:InDOl/CpxZn=1.44-2.19;InDOl/CpxMn=0.21-0.40,InDOl/CpxTi=4.76-5.61,InDOl/CpxNi(平均值)=2.20.透辉石中Ti/Zr=42-103,低于原始地幔值,由地幔隐性交代作用造成。 相似文献
6.
《Applied Geochemistry》2006,21(8):1410-1431
Laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) was used to determine major and trace element concentrations in rock varnish samples from the Lahontan Range, near Fallon, NV and from a remote wilderness area near the San Juan River, in southeastern Utah. The data indicate that rapid LA-ICPMS analyses provide ample analytical resolution for semi-quantitative compositional determinations of both trace and major elements in the varnish despite the presence of a rock substrate component in most analyses. The overall major element contents of rock varnish from the two localities are grossly similar to rock varnish from other locations analyzed by solution ICPMS, electron microprobe, and energy dispersive scanning electron microscopy (SEM). Differences between microprobe and LA-ICPMS analyses may stem from different sampling scales and different degrees of substrate involvement. It was possible to detect significant variations in trace element contents in the rock varnish samples. The Lahontan Range is situated within a belt of W mineralization, and varnish from that locality contained significantly higher W and Mo contents than varnish from localities outside the W belt. Lead, Tl, Bi, Cd and As contents of varnish-coated pebbles from near the San Juan River in southeastern Utah, varied by an order of magnitude as a function of the position of the sampling site on the pebble. Elevated heavy element contents on the skyward-facing varnish surfaces indicate that heavy elements may be preferentially scavenged at the locations most likely to receive direct inputs of atmospherically-deposited airborne particulates. The source of metal-rich airborne particulates, in this case, is probably any one of several large coal-fired power plants in the Four Corners region, proximal to the San Juan study area. These patterns indicate that rock varnish chemistry is influenced by atmospherically-derived fluxes of both dissolved and particulate constituents, and that rock varnish can be used as a passive environmental indicator for a wide variety of elements, in much the same manner as moss and lichens. 相似文献
7.
8.
东昆仑造山带蛇绿岩矿物学特征及其岩石成因讨论 总被引：3，自引：0，他引：3
首次对东昆仑复合造山带不同时代蛇绿岩主要造岩矿物橄榄石、辉石、斜长石进行了系统的矿物化学研究 ,查明了不同蛇绿岩带在矿物成分上的差异 ,对清水泉蛇绿岩带和布青山蛇绿岩带单斜辉石、斜方辉石、斜长石进行了矿物稀土、微量元素的研究 ,阐明了矿物稀土、微量元素与全岩稀土、微量元素的关系 ,证明了在以辉石和橄榄石为主的橄辉岩中 ,单斜辉石的稀土元素基本上代表了全岩的稀土元素。根据地幔岩石中矿物成分特征 ,对不同蛇绿岩带地幔类型进行了讨论 ,并根据实测的辉石、斜长石分配系数 ,确定了清水泉蛇绿岩带玄武岩的部分熔融定量模拟 相似文献
9.
The petrogenesis of the Fiskenaesset anorthosite body has been investigated using major and trace element data for a large range of rock types from each zone of the complex. The chemistry of these ultramafic to anorthositic cumulates is interpreted in terms of crystal fractionation of a parental, trace element impoverished, tholeiitic magma, involving crystallisation of the cumulus phases olivine, orthopyroxene, clinopyroxene and (dominant) plagioclase feldspar. Amphibole appears not to have been a significant cumulus phase at any stage of crystallisation of the body, the abundant amphibole found in the rocks of the complex being produced by primary intercumulus crystallisation, supplemented by secondary metamorphic recrystallisation. Similarly, magnetite is unlikely to have been a significant early cumulus phase, although, together with chromite, it crystallised as a cumulus phase at high stratigraphic levels in the complex. The metamorphism appears to be largely isochemical, although sub-solidus metamorphic re-equilibration of the REE can be demonstrated on a grain-size scale.The spatial and temporal association between the anorthosite complex and the bordering metavolcanic amphibolites is matched by a strong similarity between the observed trace element chemistry of the amphibolites and the trace element chemistry of calculated successive liquids for the complex. This is taken to suggest a genetic relationship between the evolution of the anorthosite complex and enclosing amphibolites. The presence of trace element impoverished amphibolites (which are not cumulates) with trace element abundances comparable to those of the suggested parental liquid to the anorthosite complex, is used to derive a major element composition for the primary Fiskenasset magma. This composition approximates a moderately aluminous tholeiitic basalt, which may have been generated by hydrous fusion of previously depleted mantle. This primary magma underwent crystal fractionation under low pressure conditions, allowing the development of extensive plagioclase cumulates.The Fiskenaesset anorthosite, and similar bodies, cannot represent a cumulate residue complementary to the enclosing voluminous tonalitic gneisses, which have a calc-alkaline chemistry controlled by high pressure crystal liquid fractionation. Rather, the association between the cumulate layered complex and bordering supracrustal sequence may imply an ancient ocean crust analogue for the development of this component of Archaean high-grade terrains. It is suggested that slices of such Archaean ocean floor may be emplaced laterally into the base of the continental crust during subduction of oceanic lithosphere at Cordilleran type continental margins. 相似文献
10.
11.
野马泉楚鲁套海岩体分布于昆北断裂以北祁漫塔格岩浆弧东部,侵位于奥陶纪祁漫塔格群—志留纪滩间山群碎屑岩组和晚三叠世鄂拉山组,岩石类型主要为花岗斑岩和花岗闪长斑岩。岩石地球化学结果表明该岩体属准铝质—过铝质的钙碱性岩石系列,为A型花岗岩;稀土元素球粒陨石标准配分图呈右倾式,轻稀土富集,重稀土较为平坦,出现强烈Eu亏损;由多种主量及微量元素进行相关的构造环境判别,为后造山的伸展构造环境。在楚鲁套海花岗斑岩中获得了U-Pb同位素年龄为(256.0±9.6)M a,确定其侵位时代为晚二叠世。 相似文献
12.
贵州喀斯特与非喀斯特农业生态地质环境质量对比研究 总被引：3，自引：0，他引：3
为寻求喀斯特地区农产品低劣的根源,通过调查和采样测试对比研究了贵州碳酸盐岩和非碳酸盐岩地质环境和农作物产品质量的差异。结果表明:（1）非碳酸盐岩的微量元素含量为10.894 2×10-3,而碳酸岩的为35.322 7×10-4;非碳酸盐岩地区耕作土中有效态微量元素含量为3.260 5×10-4,碳酸盐岩分布区的耕作土仅为1.014×10-4,彼此相差3倍;（2）优质农作物多产于非碳酸盐岩地区,随机调查贵州省内38个优质水稻产地,有33个位于非碳酸盐岩地区,仅有5个在碳酸盐岩区。茶叶、马铃薯、西瓜等也有此类规律。由此认为,喀斯特环境缺乏多种矿物营养元素,是形成其农作物质量低下的根本原因,也是贵州喀斯特农业生态环境脆弱的内在原因。 相似文献
13.
中甸晚三叠世图姆沟组岩石化学与构造环境 总被引：9，自引：0，他引：9
本文对中甸东部晚三叠世图姆沟组深水浊积岩和弧火山岩、微量和稀土元素进行研究,投点多落入再旋回造山带物源区;微量和稀土元素与图解中多接近大陆岛弧区;常量元素分析与相关图解接近活动大陆边缘和大陆岛弧环境,与火山岩的大地构造环境具有相同的结论。图姆沟组为甘孜—理塘洋盆向西俯冲消减,中甸褶皱带东缘由被动大陆边缘转化为活动大陆边缘过程中形成的岛弧火山—沉积岩系。 相似文献
14.
吉林省小石人金矿区微量元素地球化学特征 总被引：3，自引：0，他引：3
以吉林省小石人金矿区内不同类型岩(矿)石微量元素测试结果为基础,从数据结构和空间结构两方面,对微量元素的地球化学特征进行探讨。统计参数表明:所观测元素在矿区内具有明显的浓集、富集特点,在不同类型岩(矿)石中元素的分布分配也不尽相同。依据分布分配特点,可将矿区内的岩(矿)石分为正常岩石、弱蚀变岩石和强蚀变/矿化岩石3类。多元统计分析成果揭示:所观测元素都参与了金的成矿活动,但行为特点有所差异。依据多元统计特征,可将微量元素分为3个组合类型:Au、As、Sb、Bi、Hg、Mn,Cu、Pb、Zn、Ag,Co、Ni、V;第一组合为成矿成晕组合,第二组合为金的多金属矿化组合,第三组合为黄铁矿化蚀变组合;元素组合也对应于不同的矿化阶段,指示金的成矿活动及特征。土壤、岩石地化剖面显示所观测的元素间存在空间相关性,但Mn与Au相异,其异常出现在矿化蚀变带的外侧。 相似文献
15.
主要通过清水沟-白柳沟矿田与白银厂矿田的火山岩成分、微量元素特征成矿蚀变特征、地质特征等综合分析和对比研究,从块状硫化物矿床成矿系列角度,分析和讨论了清水沟-白柳沟矿田与典型的白银厂矿田的某些相似性或可比性,以期指出清水沟-自柳沟-带进一步找矿的潜力和远景地段。结果表明,2矿田无论是在成矿时代、赋矿岩石组合方面,还是在火山机构和成矿特征等方面皆有一定的可比性。由此提出在清水沟-白柳沟地区还有发现白银厂式块状硫化物矿床的潜力,并提出尕大坂是最具找矿潜力的远景区,值得进一步投人勘查工作。 相似文献
16.
Carbonatites are believed to have crystallized either from mantle-derived primary carbonate magmas or from secondary melts
derived from carbonated silicate magmas through liquid immiscibility or from residual melts of fractional crystallization
of silicate magmas. Although the observed coexistence of carbonatites and alkaline silicate rocks in most complexes, their
coeval emplacement in many, and overlapping initial87Sr/86Sr and143Nd/144Nd ratios are supportive of their cogenesis; there have been few efforts to devise a quantitative method to identify the magmatic
processes. In the present study we have made an attempt to accomplish this by modeling the trace element contents of carbonatites
and coeval alkaline silicate rocks of Amba Dongar complex, India. Trace element data suggest that the carbonatites and alkaline
silicate rocks of this complex are products of fractional crystallization of two separate parental melts. Using the available
silicate melt-carbonate melt partition coefficients for various trace elements, and the observed data from carbonatites, we
have tried to simulate trace element distribution pattern for the parental silicate melt. The results of the modeling not
only support the hypothesis of silicate-carbonate melt immiscibility for the evolution of Amba Dongar but also establish a
procedure to test the above hypothesis in such complexes. 相似文献
17.
文章的主要内容为:(1)对高坪地区某地质剖面的钻孔岩心蚀变强度进行赋值,将所得的数据绘制成等值剖面图,分析蚀变数据在剖面上的特征;(2)通过蚀变强度数值,求出黄溪断裂带上、下盘各种蚀变之间及其与铀矿化的相关系数,得出各种蚀变之间的相关性;(3)将强蚀变岩石、弱蚀变岩石与燕山期、印支期正常花岗岩进行对比,研究蚀变岩石的化学成分及微量元素、稀土元素特征。通过综合比对研究,讨论黄溪断裂带上下盘岩石差异的原因,总结该区铀成矿规律;推测黄溪断裂上盘受矿后期构造破坏更强,且相对抬升更高;认为该区围岩中Fe3+/Fe2+和LREE/HREE值对铀矿找矿有一定的指导意义。 相似文献
18.
Trace Element and Platinum Group Element Distributions and the Genesis of the Merensky Reef, Western Bushveld Complex, South Africa 总被引：5，自引：0，他引：5
The Merensky Reef of the Bushveld Complex is one of the world'slargest resources of platinum group elements (PGE); however,mechanisms for its formation remain poorly understood, and manycontradictory theories have been proposed. We present precisecompositional data [major elements, trace elements, and platinumgroup elements (PGE)] for 370 samples from four borehole coresections of the Merensky Reef in one area of the western BushveldComplex. Trace element patterns (incompatible elements and rareearth elements) exhibit systematic variations, including small-scalecyclic changes indicative of the presence of cumulus crystalsand intercumulus liquid derived from different magmas. Ratiosof highly incompatible elements for the different sections areintermediate to those of the proposed parental magmas (CriticalZone and Main Zone types) that gave rise to the Bushveld Complex.Mingling, but not complete mixing of different magmas is suggestedto have occurred during the formation of the Merensky Reef.The trace element patterns are indicative of transient associationsbetween distinct magma layers. The porosity of the cumulatesis shown to affect significantly the distribution of sulphidesand PGE. A genetic link is made between the thickness of theMerensky pyroxenite, the total PGE and sulphide content, petrologicaland textural features, and the trace element signatures in thesections studied. The rare earth elements reveal the importantrole of plagioclase in the formation of the Merensky pyroxenite,and the distribution of sulphide. KEY WORDS: Merensky Reef; platinum group elements; trace elements 相似文献
19.
Accurate and consistent X-ray fluorescence analysis of major and trace elements using a single pressed pellet for each sample has been achieved with a wide variety of rock compositions. Counting techniques for use with data reduction and correction programs in Standard Fortran IV are described; the latter depend throughout on data developed from a wide range of standard rock compositions. A comparison of ten major and fifteen trace element analyses for U.S.G.S. standard rocks with averages taken from the literature testifies to the precision of these techniques. 相似文献
20.
云南白马寨镍矿区煌斑岩地球化学Ⅰ.主要元素和微量元素 总被引：9，自引：1，他引：9
云南白马寨镍矿区煌斑岩呈岩墙和岩脉穿切矿区各时代地层、基性-超基性岩和矿体，为成矿期后产物；采自矿区不同中段和不同产状的煌斑岩具有相似矿物组合，岩石类型均为云煌岩；岩石化学特征表明岩石均为钾质-富钾质钙碱性煌斑岩；微量元素配分模式为相似的“骆峰型”，与MORB相比，富集LILE和HPSE；REE配分模式为相似的LREE富集型；主要元素和微量元素与镁指数(M值)之间存在一定的相关关系；在La—La／Sm图中样品既有水平分布趋势、也有倾斜分布趋势。总体上，该区煌斑岩为相同岩浆源区的产物，源区地幔部分熔融程度和岩浆结晶分异作用对岩石主要元素和微量元素地球化学性质均有一定的影响。比较老王寨金矿区煌斑岩形成地质背景、岩石类型、主要元素和微量元素地球化学特征，认为两地区煌斑岩地幔源区具有相同或相似、的性质。 相似文献