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1.
《Applied Geochemistry》1986,1(4):493-502
Five Carlin-type sediment-hosted precious metals deposits from the western United States have been analyzed for Tl, Rb, K, Sr, Au, and Ag, and the relationship between Tl, Rb, and K in mineralized and unmineralized rocks has been studied. The Carlin-type gold deposits studied include Carlin, Alligator Ridge, and Jerritt Canyon deposits of Nevada, Mercur deposit of Utah, and North Moccassin deposits of Montana.The mineralized rocks of all five deposits contain significantly high contents of Tl and low K/Tl and high Tl/Sr ratios. The oxidized mineralized rocks of the Carlin and Mercur deposits have higher contents of Tl than carbonaceous rocks while siliceous rocks from most of the deposits contain the lowest Tl concentrations.The K/Tl ratio and the relationship between Tl, Rb, and K can be used to separate mineralized and unmineralized rocks into two distinct populations in order to outline, successfully, potential mineralized areas. The data presented in this paper suggest that Tl is probably a more useful indicator element than Au and other associated elements, at least under certain situations. 相似文献
2.
Sami Hamed Abd El Nabi 《Arabian Journal of Geosciences》2013,6(4):1249-1261
The radiometric responses of the Gebel (G., which means mountain in Arabic) Meatiq area display the overall high radiation of the high grade metamorphic Um Ba’anib granite gneiss, metasediments, as well as Arieki adamellite rocks. Whereas, the low grade metamorphic ophiolitic nappes country reveal the lowest radiometric response. The eU, eTh, and K contents tend to increase with the youthfulness of the plutons with a maximum amounts in the more alkali varieties, e.g., Arieki adamellite (580 Ma), then the high grade metamorphic rocks of the younger Meatiqian orogeny (626?±?2 Ma). Also, these rocks reveal that the major radiometric anomaly with exposure rates ≈139 nGy/h, more than double of the global terrestrial values. While, the low grade metamorphic ophiolitic rocks reveal the lowest average exposure rates ≈46.8 nGy/h. The areas of high gamma ray values of F-parameter of Efimov (K × U/Th), ternary composite map, K map, K/eTh, and K/eU ratios maps are related to K enrichment conditions during formation (diagenesis) or deformation of the high grade metamorphic rocks and the Arieki adamellite intrusion. From the geochemical point of view, these areas are associated with rocks that are characterized by high-K calc-alkaline, calc-alkaline affinity, and enriched in REE. 相似文献
3.
TWO TYPES OF CENOZOIC HIGH-K MAGMATINSM IN EASTERN TIBET:IMPLICATIONS FOR THE NATURE OF MANTLE SOURCES1 ArnaudNO ,VidalP ,TapponnierP ,etal.ThehighK2 OvolcanismofnorthwesternTibet:geochemistryandtectonicim plications[J] :EarthPlanetSciLett,1991,11:351～ 36 7.
2 DengW .CenozoicvolcanicrocksinthenorthernNgaridistrictoftheTibet Discussionontheconcurrentsubduction[J] .Ac taPetrolSinica ,1989( 3) :1～ 11.
3 HarrisonTM ,LeloupPH ,RyersonFJ,… 相似文献
4.
A comparison of K, Rb, Th and U concentrations in granulite facies rocks with those of unmetamorphosed common rock types shows that depletion of these elements in granulites is variable. K/Rb ratios for granulites are generally higher than unmetamorphosed rocks, but K/Rb ratios only reach extreme values when K < 1%. The covariation of K/Rb ratio with K concentration suggests that protolith composition, hence mineralogy, is very important in controlling the degree of Rb depletion in granulites. Felsic granulites exhibiting extreme K/Rb ratios are mainly Archean, reflecting the high abundance of low K felsic rocks in Archean terrains. The Scourian granulites of Scotland all have very high K/Rb ratios and cannot be considered to be representative of granulite facies terrains. It is impossible from this data set to state conclusively whether K is depleted in granulites; K/La ratios of granulites show complete overlap with igneous rocks. Th/U ratios in many granulites are greater than 4, indicating U loss relative to Th. Felsic granulites with low Th/U ratios also have high La/Th ratios, indicating that these granulites have been depleted in Th. The low Th/U ratios of these rocks may reflect retention of Th and U in resistant accessory phases. 相似文献
5.
北京市凤鸵梁-四海地区东岭台组火山岩岩石化学特征 总被引：1，自引：0，他引：1
根据 TAS图解 ,北京市北部凤鸵梁 -四海地区东岭台组火山岩属于流纹岩 -粗面岩 -粗安岩组合。该套火山岩既不属于钾玄岩系列 ,也不是典型的高钾钙碱性系列或碱性橄榄玄武岩系列 ,在总体上应属于钾质碱性系列和富钾质拉斑系列相混合的过渡岩石组合。该套火山岩轻稀土元素明显富集。粗安岩类岩石没有负铕异常或负铕异常不明显 ,而流纹岩和粗面岩存在明显的负铕异常。凤鸵梁 -四海地区东岭台组酸性火山岩形成于造山晚期或后造山期初始阶段。 相似文献
6.
大兴安岭北段新林战备村地区广泛发育晚中生代火山岩及花岗岩体。LA-ICP-MS锆石U-Pb测得战备村花岗岩体侵位年龄为121.0±0.8 Ma,其周围出露的白音高老组流纹岩喷发年龄为136.9±1.3 Ma,二者均形成于早白垩世。地球化学特征上,二者均属于过铝质高钾钙碱性-钾玄质系列,高SiO_2,富K_2O、Na_2O,低Mg、Ti,微量元素富集大离子亲石元素Rb、K、Ba及LREE,亏损高场强元素Nb、Ta、Ti及HREE,轻重稀土明显分异((La/Yb)_N=11~23.2),具中等-弱的Eu负异常(δEu=0.35~0.82),二者具同源岩浆演化的特征。结合前人研究结果,新林战备村地区早白垩世火成岩形成于后造山或碰撞后的构造环境,代表了伸展的大地构造背景,这些火成岩产出可能与蒙古—鄂霍茨克洋中侏罗世至早白垩世闭合造山后的伸展作用有关。 相似文献
7.
Alistair R. Allen 《Contributions to Mineralogy and Petrology》1979,71(1):85-98
Geochemical investigations in the Utralanama Block, an intermediate pressure granulite facies terrain in the Arunta Block, central Australia, has revealed several anomalous features, not consistent with the depletion of granitophile components generally considered to accompany granulite facies metamorphism. However, other geochemical features are indicative of depletion. The mean K2O for the Utralanama Block is exceptionally low relative to most other granulite facies terrains, but Rb contents are comparatively high. Consequently, the mean K/Rb ratio is relatively low for granulite facies terrains as is the mean Ba/Rb ratio, whilst mean K/Sr and Rb/Sr ratios are much higher than usual for such terrains. Only the K/Ba ratio shows equivalent values to depleted terrains elsewhere.Comparison of these ratios for the three main compositional groups of rocks in the Utralanama Block reveals that for mafic rocks all the above ratios are characteristic of extreme depletion, whereas, for all but the K/Ba ratio, mean ratios for the pelitic rocks, and to a lesser extent for the quartzofeldspathic rocks approach normal crustal values or values for metasomatic rocks. The abnormally high Rb/Sr ratios of these rocks compared to average crustal rocks suggest, however, that metasomatism is the cause of the anomalous geochemical features of the Utralanama Block, and this is supported by field and microstructural evidence. Thus, Rb/Sr ratios appear to be useful indicators of metasomatism where no gross mineralogical or microstructural evidence for metasomatism is obvious, and under such conditions the K/Ba ratio may be more reliable than the K/Rb ratio for indicating prior depletion of the terrain. 相似文献
8.
9.
LA-ICP-MS锆石U-Pb测年结果表明,研究区中生代火山岩可分为2期,分别是早白垩世早期（约144Ma）吉祥峰组流纹岩类和早白垩世晚期（约125Ma）上库力组流纹岩类与梅勒图组玄武岩类。早白垩世早期吉祥峰组流纹岩富硅、富碱、富钾（K2O/Na2O〉1）,富集轻稀土元素和Rb、Th、U等元素,亏损重稀土元素、高场强元素（Nb、Ta、Ti）及Sr、P,具有A型流纹岩的特征,暗示其形成于伸展环境。早白垩世晚期火山岩显示双峰式岩石组合特征,基性端元富碱、高钾,富含轻稀土元素和Rb、Ba,亏损重稀土元素和高场强元素（Nb、Ta、Ti、Y）,类似于钾玄质玄武岩,酸性端元显示A型流纹岩的特征。双峰式火山岩组合的存在暗示其形成于陆内拉张的构造环境。结合区域上中生代火山岩的空间分布规律,认为早白垩世早期火山岩的形成与蒙古-鄂霍次克缝合带的演化有关,早白垩世晚期双峰式火山岩的形成与古太平洋板块向欧亚大陆下的俯冲作用相联系。 相似文献
10.
内蒙古东北部额尔古纳地区上护林-向阳盆地中生代
火山岩LA-ICP-MS锆石U-Pb年龄和地球化学特征 总被引：9，自引：5，他引：4
LA-ICP-MS锆石U-Pb测年结果表明,研究区中生代火山岩可分为2期,分别是早白垩世早期(约144Ma)吉祥峰组流纹岩类和早白垩世晚期(约125Ma)上库力组流纹岩类与梅勒图组玄武岩类。早白垩世早期吉祥峰组流纹岩富硅、富碱、富钾(K2O/Na2O>1),富集轻稀土元素和Rb、Th、U等元素,亏损重稀土元素、高场强元素(Nb、Ta、Ti)及Sr、P,具有A型流纹岩的特征,暗示其形成于伸展环境。早白垩世晚期火山岩显示双峰式岩石组合特征,基性端元富碱、高钾,富含轻稀土元素和Rb、Ba,亏损重稀土元素和高场强元素(Nb、Ta、Ti、Y),类似于钾玄质玄武岩,酸性端元显示A型流纹岩的特征。双峰式火山岩组合的存在暗示其形成于陆内拉张的构造环境。结合区域上中生代火山岩的空间分布规律,认为早白垩世早期火山岩的形成与蒙古-鄂霍次克缝合带的演化有关,早白垩世晚期双峰式火山岩的形成与古太平洋板块向欧亚大陆下的俯冲作用相联系。 相似文献
11.
大兴安岭北端塔木兰沟组玄武质岩石的地球化学特征及构造背景 总被引：8，自引：1，他引：8
大兴安岭北部晚侏罗世塔木兰沟组玄武质岩石具有富碱（K2O＋Na2O〉5．45％），高K2O（2．15%-3．75％）、K2O／Na2O（0．48-1．12）和高的Th／Ta、Ce／Nb、Ta／Nb比值，以及强烈富集大离子亲石元素（LILE）和轻稀土元素（LKEE）的特征，属于钾玄质系列。现有资料分析表明，该钾玄质岩石形成于大陆板内环境。元素地球化学特征揭示，形成钾玄质岩石的原生岩浆经过强烈的结晶分异作用，并混染了前中生代的基底物质。 相似文献
12.
报道的高钾-钾玄质火山岩位于狮泉河镇南东方向约20km处,向东延伸。高钾-钾玄质火山岩Si O2变化于60.35%~68.68%之间,属中酸性岩范畴;具有高的K2O+Na2O含量(8.8%~10.66%),K2O/Na2O值在1.92~2.49之间,Mg O含量较低,介于0.88%~3.47%之间,Al2O3含量为14.02%~14.91%,属于高钾-钾玄质系列。岩石强烈富集大离子亲石元素(LILE)Rb、Ba、Th、U和轻稀土元素(LREE),高场强元素(HFSE)Nb、Ta、Ti具有明显负异常,Cr、Ni、Co相容元素含量低于或接近地壳的平均含量,结合Th/Yb-Ta/Yb、(Th×100)/Zr-(Nb×100)/Zr判别图及La-La/Yb图解,暗示岩浆源区可能为下地壳。在左左乡南东约2km处和狮泉河水泥厂北东约1km处各采集1个高钾-钾玄质火山岩样品,对其中的锆石进行LA-ICP-MS U-Pb同位素测定,得到的206Pb/238U年龄加权平均值分别为22.04±0.42Ma和22.29±0.31Ma,此年龄被解释为狮泉河一带高钾-钾玄质火山岩的喷发时代,即中新世阿启塔期。由此表明,该火山岩是印度板片向北俯冲时在狮泉河一带俯冲板片断离,岩浆发生部分熔融的产物。 相似文献
13.
Geochemistry of the tonalitic and granitic rocks of the Nova Scotia southern plutons 总被引：1，自引：0，他引：1
Carlos A.R de Albuquerque 《Geochimica et cosmochimica acta》1977,41(1):1-13
In southern Nova Scotia, tonalite, trondhjemite, granodiorite and granite intruded metasedimentary rocks of the Appalachian belt during the Acadian orogeny. The mineral assemblages of these metasedimentary rocks define the staurolite-in (or staurolite + cordierite-in) isograd of the amphibolite facies of the low-pressure, intermediate-type of regional metamorphism.The chemical compositions of these tonalitic to granitic rocks indicate that the magmas before and possibly during crystallization were under relatively high pressures (3.5–6.5 kbar) and at temperatures above ‘minimum melt’ temperatures, possibly in the range 670–730°C, with exception of the tonalitic magma for which a higher temperature of formation is required.These rocks show many geochemical affinities such as relatively high Na/K ratios and similar K/Rb ratios and REE abundances. The REE patterns are moderately fractionated, with a negative Eu anomaly.An origin by partial melting of the metasedimentary rocks of the orogenic belt is postulated for these rocks in the light of the geochemical evidence. This hypothesis has been tested by application of a quantitative model of equilibrium between granitic melts and probable residual material. 相似文献
14.
黑龙江省黑河地区广泛发育侏罗-白垩纪火山岩,但是该火山岩的岩石组合、成因和所表征的大地构造环境目前有很大的争议。本文对该套火山岩开展详细的岩石学、岩石地球化学等研究。该火山岩形成于早白垩世,主要以安山岩英安岩流纹岩为主,包含英安岩、安山岩、粗面岩、流纹岩、安粗岩、玄武安山岩、粗面英安岩、钾玄岩、歪长粗安岩,因此属于弧火山岩的组合。该区火山岩主要为亚碱性系列,岩石Na2O/K2O比值一般>1.2。A/CNK在1附近,为准铝质过铝质岩石。SiO2 TFeO/MgO图上既有钙碱性系列(包括低铁钙碱性系列),又有拉斑系列。SiO2 K2O图上主要为中钾钙碱高钾钙碱系列。SiO2 (Na2O+K2O-CaO)图上主要为钙碱系列、碱钙系列和碱性系列,在SiO2 MgO图中主要落入实验玄武岩的局部熔融范围和镁安山岩系列范围。痕量元素蛛网图显示富集大离子亲石元素,K、La、Zr、Hf、Tb、Tm为峰,亏损Nb、Ta、Ti、Y、Yb等高场强元素。稀土元素球粒陨石标准化配分模式为缓右倾型的模式,轻稀土相对富集,重稀土内部分馏不明显,具有微弱负Eu异常。大部分岩石具有高Sr低Y的特征,其中一些岩石具有adakite岩的特征。上述特征均指示弧火山岩的特征。结合构造环境判别认为该火山岩形成于与洋俯冲有关的环境。推测岩浆可能的源区为俯冲的洋壳、上覆的地幔楔、兴安弧的下地壳。 相似文献
15.
Airborne gamma-ray and magnetic anomaly signatures of serpentinite in relation to soil geochemistry, northern California 总被引：2，自引：1，他引：1
Serpentinized ultramafic rocks and associated soils in northern California are characterized by high concentrations of Cr and Ni, low levels of radioelements (K, Th, and U) and high amounts of ferrimagnetic minerals (primarily magnetite). Geophysical attributes over ultramafic rocks, which include airborne gamma-ray and magnetic anomaly data, are quantified and provide indirect measurements on the relative abundance of radioelements and magnetic minerals, respectively. Attributes are defined through a statistical modeling approach and the results are portrayed as probabilities in chart and map form. Two predictive models are presented, including one derived from the aeromagnetic anomaly data and one from a combination of the airborne K, Th and U gamma-ray data. Both models distinguish preferential values within the aerogeophysical data that coincide with mapped and potentially unmapped ultramafic rocks. The magnetic predictive model shows positive probabilities associated with magnetic anomaly highs and, to a lesser degree, anomaly lows, which accurately locate many known ultramafic outcrops, but more interestingly, locate potentially unmapped ultramafic rocks, possible extensions of ultramafic bodies that dip into the shallow subsurface, as well as prospective buried ultramafic rocks. The airborne radiometric model shows positive probabilities in association with anomalously low gamma radiation measurements over ultramafic rock, which is similar to that produced by gabbro, metavolcanic rock, and water bodies. All of these features share the characteristic of being depleted in K, Th and U. Gabbro is the only rock type in the study area that shares similar magnetic properties with the ultramafic rock. The aerogeophysical model results are compared to the distribution of ultramafic outcrops and to Cr, Ni, K, Th and U concentrations and magnetic susceptibility measurements from soil samples. Analysis of the soil data indicates high positive correlation between magnetic susceptibilities and concentration of Cr and Ni. Although the study focused on characterizing the geophysical properties of ultramafic rocks and associated soils, it has also yielded information on other rock types in addition to ultramafic rocks, which can also locally host naturally-occurring asbestos; specifically, gabbro and metavolcanic rocks. 相似文献
16.
S.A. Drury 《Chemical Geology》1973,11(3):167-188
The metamorphism and geochemistry of the major components of a small area of granulite facies rock are described and discussed, and a chemical model for the evolution of anomalous trace element distributions in such materials is suggested. The local complex was subjected to medium to high pressure granulite facies metamorphism between 2,900 and 2,600 m.y. All the analysed granulite facies rocks from Tiree; acid to intermediate gneisses, basic metamorphic rocks, and granitic rocks, have anomalous chemistries, being depleted in K, Rb, Nb, Y and Th, and have high K/Rb, Ba/Rb and Ca/Y ratios, and very low K/Ba and Rb/Sr ratios relative to normal portions of the upper continental crust. The gneisses seem to have been enriched in Ba and Sr.The chemical features of the rocks are considered to reflect their stable mineral assemblages in the granulite facies, and to be representative of deep-level crustal materials. The geochemical peculiarities of the complex may have been largely controlled by an upward intergranular diffusion, or “degassing” caused by high-grade metamorphism. It is suggested that such diffusion may have been active at the crust/upper mantle interface, some diffused material of mantle origin accounting for certain chemical oddities typical of Lewisian and some other Precambrian granulite facies rocks. 相似文献
17.
东南沿海中生代火山岩带地球化学特征 总被引：1，自引：0，他引：1
中国东南沿海位于太平洋板块和欧亚板块的结合处,广泛分布着中生代火山岩,并伴随有大规模的成矿作用。酸性火山岩占绝对优势,基性中性火山岩仅零星出露。酸性和中性火山岩为一套富碱、富钾、富铝、低钛的高钾钙碱性系列,基性火山岩为一套富硅贫碱的高钾和中钾钙碱性系列。从基性到酸性火山岩稀土分馏和铕的负异常逐渐加剧。基性火山岩贫Nb、Zr、Y,弱富集Ba、Hf、Th、Ce。中性火山岩和酸性火山岩贫Ba、Ti、P、Nb、Zr、Ta、Sr,强烈富集Pb。通过主量、微量和稀土元素的研究认为,基性火山岩和酸性火山岩为独立的岩浆起源,在中生代,东南沿海广泛存在着玄武岩的底侵作用,给下地壳提供了大量的热源,从而诱发了下地壳重熔,形成了大量的酸性火山岩。中性火山岩由酸性和基性岩浆混合形成,其地球化学特征主要受酸性岩浆的制约。 相似文献
18.
中国东北地区中生代火山岩岩石学特征与盆地形成 总被引：41，自引：3，他引：38
中国东部广泛分布中生代火山岩,它是环太平洋火山作用的重要组成部分。东北地区是中生代火山岩分布最广泛的地区之一,其形成时代从晚三叠世到晚白垩世,其中晚侏罗世—早白垩世是火山作用最强烈的时期。中生代火山岩主要有高钾钙碱性火山岩系列和钾玄岩系列,并以高钾钙碱性火山岩为主。岩石类型主要有钾玄岩、安粗岩、粗面岩、橄榄粗安岩、英安岩和流纹岩。从东向西火山岩表现出了一个化学组成上的极性。岩石的Ｔｉ、Ｔａ含量低和富Ｋ、Ｒｂ等,以及构造判别图解表明该区火山岩属造山带火山岩。上述特征表明,东北地区中生代火山活动属于与伊佐奈崎（Ｉｚａｎａｇｉ）板块俯冲作用有关的挤压造山。与火山岩共存的早白垩世的Ａ型花岗岩表明,早白垩世东北地区处于拉伸构造环境。因此,松辽、海拉尔以及二连等盆地的形成与早白垩世造山带的崩塌有关。 相似文献
19.
A. W. Webb 《Australian Journal of Earth Sciences》2013,60(1-2):187-193
K‐Ar total rock age determinations have been made on a sequence of metasedimentary rocks resting on a 2350 m.y.‐old basement in southern Eyre Peninsula, South Australia. The metasediments have an Rb‐Sr age of 1785 m.y., but K‐Ar isochrons suggest that relatively high temperatures persisted for a further 250 million years before the rocks became systems closed to K and Ar diffusion. A significant amount of 40Ar was trapped in the metasediments at the time of closure of the K‐Ar system, 1550 million years ago. 相似文献
20.
赣东北地区早白垩世火山岩的岩石学及岩石化学特征 总被引：1，自引：0，他引：1
岩石学及岩石化学特征表明，赣东北地区早白垩世火山岩及次火山岩主要有：玄武岩、伊丁石化橄榄玄武岩、橄榄玄武粗安岩、粗面玄武岩、安粗岩、粗面英安岩、粗面岩、流纹岩、凝灰岩及花岗斑岩等，可划分为高钾钙碱性、橄榄安粗岩和碱性玄武岩3个系列。高钾钙碱性系列富Si、K，贫Mg、Fe、Ca、Al；橄榄安粗岩系列和碱性玄武岩系列富碱，尤其富K，富Al、Ti，贫Si。相比之下，橄榄安粗岩系列比碱性玄武岩系列更富K、Al、Ti、Si。本区复杂的火山岩很可能是晚中生代时期古太平洋巨大板块中Faralong、Izanagi、Kula等板块相对亚洲大陆走滑和斜向俯冲及在大陆内产生的NE－NNE向平移剪切－伸展拉张的结果。 相似文献