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1.
华北板块北缘中段早中二叠世的构造属性：来自花岗岩类锆石U-Pb年代学及地球化学的制约 总被引：6，自引：5，他引：1
内蒙古温都尔庙南-铁沙盖黑云角闪石英闪长岩和角闪黑云花岗闪长岩位于华北板块北缘中段晚古生代构造岩浆活动带中;锆石LA-ICP-MS U-Pb定年结果显示,其形成时代分别为271.8±2.4Ma,271.4±1.3Ma、268.7±1.3Ma。主量元素SiO2含量61.42%~71.73%,K2O含量3.10%~5.11%,K2O/Na2O值介于0.93~1.96之间,Mg#值介于42.54~49.93之间,A/CNK为0.90~1.03;副矿物为锆石、磷灰石和磁铁矿,属亚碱性高钾钙碱性系列、I型花岗岩类;富集轻稀土(LREEs)、大离子亲石元素(LILEs,Cs、Rb、K、Ba、Th和U),亏损重稀土元素(HREEs)及高场强元素(HFSEs,Nb、Ta和Ti),弱Eu负异常(δEu=0.55~0.95),形成于活动大陆边缘弧环境,是上地壳部分熔融的产物。黑云角闪石英闪长岩和角闪黑云花岗闪长岩中发育大量暗色微粒包体(黑云闪长岩),包体可能是岩石圈地幔部分熔融的产物,相对于寄主岩石贫Si、K富Fe、Mg、Ca、Ti、大离子亲石元素(LILEs,Rb、Cs、Sr和U)和高场强元素(HFSEs,Nb、Ta、Zr、Hf)。本文花岗岩类的侵位反映了早中二叠世古亚洲洋俯冲于华北板块北缘之下及岩浆混合作用的岩浆事件。 相似文献
2.
河南嵩山地区新太古代TTG质片麻岩的成因及其地质意义：来自岩石学、地球化学及同位素年代学的制约 总被引：15，自引：10，他引：5
河南嵩山地区位于华北克拉通南缘,是我国记录前寒武纪地质的典型地区之一。该区广泛出露新太古代TTG质片麻岩套,主要以英云闪长岩类为主,闪长岩类次之,测得的锆石SHRIMP年龄在2600~2500Ma。该套TTG质片麻岩富Na2O(3%~7%)、SiO2(>67%)、贫铁、镁,高的Na2O/K2O比值（多在1.5~5.2）,Al2O3=13.72%~16.37%,A/CNK=0.97~1.21,属英云闪长岩-奥长花岗岩系列,显示新太古代富铝型TTG岩石特征。岩石富Sr (平均433×10-6),Rb/Sr比值(<0.5) 较低,Sr/Y比值高(平均165),Nb、Ta和Ti负异常,∑REE偏低,强烈分异((La/Yb) N=27~150),基本无Eu异常,低的Nb/Ta(14左右)、La/Nb (平均约为7)比值及其它微量元素特征表明其与岛弧或大陆边缘弧玄武质岩石特征相似。全岩Nd同位素和锆石Hf同位素数据显示岩石源区是来自亏损地幔的约2.66Ga的初生地壳;Mg#值变化较大反映存在地幔楔不同程度的混染。地球化学特征指示该岩浆是在较高温度和压力(约700~1000℃,>1.5Gpa)下由俯冲的含水玄武质洋壳部分熔融形成,残留相中有石榴石和角闪石而不含斜长石。嵩山地区TTG片麻岩的这种成因机制表明当时陆壳以水平方式增生,也说明在随后的2.5Ga左右微陆块碰撞拼合事件之前不同陆块之间很可能被一个古大洋所分隔。 相似文献
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A型花岗岩的岩石成因对于评估伸展构造背景下的岩浆作用极为关键。我们对藏南特提斯喜马拉雅带内的哲古错花岗闪长岩进行了锆石U-Pb定年、全岩地球化学和同位素（Sr和Nd）组成分析测试。结果表明,该花岗闪长岩形成于260.3±2.8Ma,并且被一约146Ma的闪长岩侵入。该花岗闪长岩属于高K钙碱性、偏铝质系列,其A/CNK和A/NK分别为0.74~0.76和1.87~2.72,富集轻稀土元素（LREE）,亏损重稀土元素（HREE）,有明显的Nb、Ta和Ti的负异常,Zr和Hf正异常,εNd（t）值为+1.1~+2.3;岩相学也显示出碱性花岗岩特征。以上所有特征揭示了该花岗闪长岩和A2型花岗岩相似,但其与典型的弧岩浆岩不同,而是与伸展构造背景下形成的岩浆岩类似。哲古错花岗闪长岩的源区是为经亏损地幔物质改造过的沉积岩或变沉积岩,基于本研究数据及已有数据表明,本研究中的晚二叠世酸性岩浆作用是一次与冈瓦纳大陆北缘裂解和新特提斯洋开启有关的岩浆活动。 相似文献
4.
英云闪长岩-奥长花岗岩-花岗闪长岩(TTG)是地球早期大陆地壳最重要的组成部分。TTG的Nb/Ta比值变化不仅与它的成因相关,而且与早期构造环境和地壳分异过程关系紧密。本文选择阴山地块出露的TTG片麻岩及下地壳斜长角闪岩/麻粒岩包体作为研究对象,开展了寄主花岗闪长岩和同源镁铁质包体中的角闪石和黑云母的原位微区矿物的微量元素分析工作,以及TTG与非同源斜长角闪岩包体的全岩主微量元素分析工作。矿物化学研究结果表明,花岗闪长岩和同源镁铁质包体的角闪石具有相似的Mg#值,但是两者具有明显不同的Nb/Ta比值。镁铁质包体中的角闪石更富Cr、Ta,Nb/Ta比值为30~50;TTG岩石中的角闪石Cr和Ta含量偏低,但具有更高的Nb/Ta比值(38~70)。TTG和镁铁质包体中的角闪石Cr含量与Nb/Ta具有较好的负相关关系。全岩地球化学分析结果揭示,TTG片麻岩的具有高Nb/Ta比值(13~65,平均值31),斜长角闪岩和麻粒岩包体具有变化的Nb/Ta比值(10~56)。太古宙绿岩带中玄武质岩石的Nb/Ta平均值为~15,阴山地块斜长角闪岩和麻粒岩包体具有高的Nb/Ta比值,反映了这些代表基性下地壳的岩石经历了部分熔融作用或后期的交代作用,使其Nb/Ta比值发生改变。研究区具有高Nb/Ta比值的TTG可能来源于高Nb/Ta比值基性下地壳部分熔融,并继承了源区高Nb/Ta比值的特征。通过本文研究揭示,高Nb/Ta比值的TTG并非一定形成于俯冲带洋壳榴辉岩相部分熔融,下地壳富角闪石和黑云母的岩石部分熔融是形成高Nb/Ta比值TTG的一种重要途径。 相似文献
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西藏措勤尼雄矿田滚纠铁矿侵入岩LA-ICP-MS 锆石 U-Pb年龄与地球化学特征 总被引：9，自引：3，他引：6
本文分析了尼雄矿田滚纠铁矿与成矿相关的花岗闪长岩和二长花岗岩主量元素、微量元素并对其进行锆石LA-ICP-MS U-Pb定年。结果显示,岩石富硅(SiO2平均分别66.76%和70.98%)、富碱(ALK平均为6.28%和7.70%),铝饱和指数均小于1.1,属中高K钙碱性I型花岗岩。两者具相似的稀土元素球粒陨石标配分模式图和微量元素原始地幔蛛网图,∑REE较低(∑REE分别是 130.6×10-6和134.3×10-6),弱Eu负异常(δEu分别为0.84和0.88),弱-中等轻重稀土分馏,(La/Yb)N分别平均8.07和6.72。 Rb、Pb、Th等大离子亲石元素和稀土元素富集,Ba和U、Nb、Ta、P 、Ti等高场强元素亏损,显示弧岩浆作用特点,指示岩石形成于弧后伸展环境,岩浆源区具壳幔混源的特征。LA-ICP-MS锆石U-Pb测年显示花岗闪长岩和二长花岗岩分别形成于113.6±1.2Ma和112.6±1.6Ma,属早白垩世晚期岩浆活动产物。结合区域地质资料,认为滚纠铁矿与成矿相关的花岗闪长岩和二长花岗岩因班公湖-怒江洋壳向南俯冲,并于~113Ma发生冈底斯陆壳和羌塘陆壳对接,已俯冲的班公湖-怒江洋壳发生板片回转,导软流圈地幔流体上涌,其所带来的巨大热能引发岩石圈地幔和上覆地壳发生部分熔融,形成以壳源为主的壳幔混源岩浆,在弧后拉张环境下上侵形成。 相似文献
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江日嘎玛花岗侵入岩位于巴颜喀拉-松潘-甘孜造山带北部,侵位于中三叠世甘德组三段地层中。本文通过对江日嘎玛花岗侵入岩进行岩相学、岩石地球化学及年代学研究,探讨其成因及构造环境。研究表明,江日嘎玛花岗侵入岩,具有较高的SiO2(w(SiO2)=69.63%~71.05%),A/CNK=1.017~1.043,铝饱和指数<1.1,属弱过铝质高钾钙碱性Ⅰ型花岗岩;岩石具有明显富集Zr、Hf、Ba,亏损Nb、U、Ta、Ti、Rb、K的特征,并且具有负Eu异常;花岗岩锆石SHRIMP U-Pb测年为222.5 Ma±1.9 Ma,表明岩浆侵位时代为中生代晚三叠世,形成于碰撞造山后期地壳减薄环境中。 相似文献
7.
新疆伊宁地块晚泥盆世火山岩的确认及其地质意义 总被引：3，自引：0，他引：3
最新发现的泥盆纪火山岩位于西天山伊犁地块北缘,主要岩石组成为流纹岩,英安岩夹少量安山岩。锆石LA-ICP-MS U-Pb定年结果显示,尼勒克北流纹岩类的形成时代一致,分别为369.7±4.9Ma,363.4±2.5Ma,均为晚泥盆世。岩石SiO2含量较高且变化范围较宽,Al2O3含量较高,富碱,贫镁和钙,高FeOT/MgO+FeOT比值,低TiO2,里特曼指数δ较小(1.09~2.88),A/CNK值变化较大(0.8~1.46),属于钙碱性过铝-准铝质低钛流纹岩类。稀土元素总量(∑REE)变化较大(80.66×10-6~241.8×10-6),稀土配分模式为轻稀土富集右倾((La/Yb)N=5.96~7.82),铕负异常明显(Eu/Eu*=0.47~0.86),相对富集Rb、Th、K等大离子亲石元素,亏损Nb、Ta、Ti等高场强元素,较高的Rb/Sr、Nb/Ta和Th/Ta比值(分别为0.18~5.15,11.18~13.96,3.54~9.5),较低的Ti/Zr、Ti/Y及Ta/Yb比值(分别为4.95~25.79,43.7~295.5,0.45~1.29),这些地球化学特征表明其可能为上地壳部分熔融的产物,源区残留物组成可能为斜长石和角闪石,同时显示其具有大陆边缘弧亲缘性,这与西天山在早石炭世处于岛弧环境相匹配,即在晚泥盆世-早石炭世期间,准噶尔洋向伊犁-中天山地块之下发生俯冲,形成了伊犁地块北缘的大陆边缘弧岩浆带。尼勒克北晚泥盆世流纹岩类成岩时代的确定及构造环境分析为进一步认识伊犁地块北缘地区的构造演化提供了新的证据。 相似文献
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对出露于阿尔泰造山带南缘可可托海地区二厂房岩体中的黑云母花岗闪长岩进行了LA-ICP-MS锆石U-Pb定年和岩石地球化学分析。结果显示,锆石的206Pb/238U年龄加权平均值为398.0±3.5 Ma（MSWD=1.3）,表明该岩体形成于早中泥盆世。岩体的SiO2含量介于65.40%～69.31%之间,里特曼指数值为1.27～1.65,A/CNK值为0.92～1.02,属中钾、钙碱性、准铝质岩石。具有富集Cs、Rb、Th、U等大离子亲石元素和轻稀土元素,相对亏损重稀土元素和Nb、Ta、Zr、Hf等高场强元素,负Eu异常明显（δEu=0.48～0.65）的岛弧岩浆岩特征。结合区域地质资料,认为二厂房岩体形成于陆缘弧构造环境,是在古亚洲洋俯冲过程中,幔源的基性岩浆底侵下地壳后使之熔融并发生了岩浆混合作用的产物。 相似文献
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大东沟金矿位于华北克拉通北缘东段。对矿区内的岩浆岩进行了锆石U-Pb年代学和岩石地球化学研究。用LAICP-MS方法,测得花岗闪长岩和石英闪长岩中锆石207Pb/206Pb年龄加权平均值分别为2147±10Ma和140.8±1.2Ma,花岗闪长岩经历了1874±18Ma的后期热液活动事件。元素地球化学测试结果显示,两者均为高钾钙碱性I型花岗岩类。石英闪长岩稀土元素配分模式为明显的右倾模式,具有弱负Eu异常,而花岗闪长岩为平坦的右倾模式,具有明显的正Eu异常,两者呈现轻稀土相对富集的特征。微量元素均富集Rb、Ba、K等大离子亲石元素。石英闪长岩表现为亏损Nb、Ta、Zr、Hf、Ti等高场强元素,而花岗闪长岩表现为Th、Nb、Ta、Ti等高场强元素亏损。结合区域大地构造背景及相关研究认为,花岗闪长岩形成于大陆弧后盆地的构造背景,主要是由约2.2Ca的岩浆底侵加热导致下地壳基性火成岩部分熔融而成;石英闪长岩形成于伊佐奈岐板块向华北板块斜向俯冲的构造背景,具有壳幔混合的特征,为俯冲带流体交代地幔,使其部分熔融,形成基性岩浆与地壳熔融物质混合而成的产物。 相似文献
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本文对内蒙古中部乌拉特中旗扎嘎乌苏地区闪长岩和花岗闪长岩进行了岩石学、 锆石U-Pb定年和岩石地球化学研究。结果表明闪长岩和花岗闪长岩都属于中钾钙碱性系列, 稀土元素（REE）丰度较高, 轻、 重稀土元素分馏明显, Eu负异常不明显, 富集大离子亲石元素（Rb、 Sr、 Ba等）和轻稀土元素（LREE）, 亏损高场强元素（Nb、 Ta、 Ti）, 与典型的岛弧岩浆岩类似。选取两件样品获得的原位锆石U-Pb测年结果分别为459.6±4.7Ma和452.6±7.0Ma, 记录了晚奥陶世古亚洲洋壳俯冲消减事件, 为研究该时期弧岩浆作用提供了新的年代学数据。 相似文献
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Between 1985 and 1991, two new mountain protected areas (MTNPA) covering more than 35,000 km2 and based on participatory management models — the Makalu-Barun National Park and Conservation Area, Nepal, and Qomolangma Nature Preserve, Tibet Autonomous Region — were successfully established through the collaborative efforts of Woodlands Mountain Institute and conservationists in China and Nepal. Characteristics common to both projects include the importance of establishing (1) effective rationales, (2) local support constituencies, (3) a senior advisory group, (4) a task force, (5) linkages between conservation and development, and (6) fund raising mechanisms. The lessons derived from the experiences of Woodlands Mountain Institute are of significant value to others in preserving MTNPA. Increased collaboration and communication between all interested in conservation, however, will remain a critical component for expanding mountain protected area coverage to throughout the world. 相似文献
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Most sulfide-rich magmatic Ni-Cu-(PGE) deposits form in dynamic magmatic systems by partial melting S-bearing wall rocks with variable degrees of assimilation of miscible silicate and volatile components, and generation of barren to weakly-mineralized immiscible Fe sulfide xenomelts into which Ni-Cu-Co-PGE partition from the magma. Some exceptionally-thick magmatic Cr deposits may form by partial melting oxide-bearing wall rocks with variable degrees of assimilation of the miscible silicate and volatile components, and generation of barren Fe ± Ti oxide xenocrysts into which Cr-Mg-V ± Ti partition from the magma. The products of these processes are variably preserved as skarns, residues, xenoliths, xenocrysts, xenomelts, and xenovolatiles, which play important to critical roles in ore genesis, transport, localization, and/or modification. Incorporation of barren xenoliths/autoliths may induce small amounts of sulfide/chromite to segregate, but incorporation of sulfide xenomelts or oxide xenocrysts with dynamic upgrading of metal tenors (PGE > Cu > Ni > Co and Cr > V > Ti, respectively) is required to make significant ore deposits. Silicate xenomelts are only rarely preserved, but will be variably depleted in chalcophile and ferrous metals. Less dense felsic xenoliths may aid upward sulfide transport by increasing the effective viscosity and decreasing the bulk density of the magma. Denser mafic or metamorphosed xenoliths may also increase the effective viscosity of the magma, but may aid downward sulfide transport by increasing the bulk density of the magma. Sulfide wets olivine, so olivine xenocrysts may act as filter beds to collect advected finely dispersed sulfide droplets, but other silicates and xenoliths may not be wetted by sulfides. Xenovolatiles may retard settling of – or in some cases float – dense sulfide droplets. Reactions of sulfide melts with felsic country rocks may generate Fe-rich skarns that may allow sulfide melts to fractionate to more extreme Cu-Ni-rich compositions. Xenoliths, xenocrysts, xenomelts, and xenovolatiles are more likely to be preserved in cooler basaltic magmas than in hotter komatiitic magmas, and are more likely to be preserved in less dynamic (less turbulent) systems/domain/phases than in more dynamic (more turbulent) systems/domains/phases. Massive to semi-massive Ni-Cu-PGE and Cr mineralization and xenoliths are often localized within footwall embayments, dilations/jogs in dikes, throats of magma conduits, and the horizontal segments of dike-chonolith and dike-sill complexes, which represent fluid dynamic traps for both ascending and descending sulfides/oxides. If skarns, residues, xenoliths, xenocrysts, xenomelts, and/or xenovolatiles are present, they provide important constraints on ore genesis and they are valuable exploration indicators, but they must be included in elemental and isotopic mass balance calculations. 相似文献
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14.
《Chemical Geology》2007,236(1-2):13-26
We examined the coprecipitation behavior of Ti, Mo, Sn and Sb in Ca–Al–Mg fluorides under two different fluoride forming conditions: at < 70 °C in an ultrasonic bath (denoted as the ultrasonic method) and at 245 °C using a Teflon bomb (denoted as the bomb method). In the ultrasonic method, small amounts of Ti, Mo and Sn coprecipitation were observed with 100% Ca and 100% Mg fluorides. No coprecipitation of Ti, Mo, Sn and Sb in Ca–Al–Mg fluorides occurred when the sample was decomposed by the bomb method except for 100% Ca fluoride. Based on our coprecipitation observations, we have developed a simultaneous determination method for B, Ti, Zr, Nb, Mo, Sn, Sb, Hf and Ta by Q-pole type ICP-MS (ICP-QMS) and sector field type ICP-MS (ICP-SFMS). 9–50 mg of samples with Zr–Mo–Sn–Sb–Hf spikes were decomposed by HF using the bomb method and the ultrasonic method with B spike. The sample was then evaporated and re-dissolved into 0.5 mol l− 1 HF, followed by the removal of fluorides by centrifuging. B, Zr, Mo, Sn, Sb and Hf were measured by ID method. Nb and Ta were measured by the ID-internal standardization method, based on Nb/Mo and Ta/Mo ratios using ICP-QMS, for which pseudo-FI was developed and applied. When 100% recovery yields of Zr and Hf are expected, Nb/Zr and Ta/Hf ratios may also be used. Ti was determined by the ID-internal standardization method, based on the Ti/Nb ratio from ICP-SFMS. Only 0.053 ml sample solution was required for measurement of all 9 elements. Dilution factors of ≤ 340 were aspirated without matrix effects. To demonstrate the applicability of our method, 4 carbonaceous chondrites (Ivuna, Orgueil, Cold Bokkeveld and Allende) as well as GSJ and USGS silicate reference materials of basalts, andesites and peridotites were analyzed. Our analytical results are consistent with previous studies, and the mean reproducibility of each element is 1.0–4.6% for basalts and andesites, and 6.7–11% for peridotites except for TiO2. 相似文献
15.
Models have become so fashionable that many scientists and engineers cannot imagine working without them. The predominant use of computer codes to execute model calculations has blurred the distinction between code and model. The recent controversy regarding model validation has brought into question what we mean by a ‘model’ and by ‘validation.’ It has become apparent that the usual meaning of validation may be common in engineering practice and seems useful in legal practice but it is contrary to scientific practice and brings into question our understanding of science and how it can best be applied to such problems as hazardous waste characterization, remediation, and aqueous geochemistry in general. This review summarizes arguments against using the phrase model validation and examines efforts to validate models for high-level radioactive waste management and for permitting and monitoring open-pit mines. Part of the controversy comes from a misunderstanding of ‘prediction’ and the need to distinguish logical from temporal prediction. Another problem stems from the difference in the engineering approach contrasted with the scientific approach. The reductionist influence on the way we approach environmental investigations also limits our ability to model the interconnected nature of reality. Guidelines are proposed to improve our perceptions and proper utilization of models. Use of the word ‘validation’ is strongly discouraged when discussing model reliability. 相似文献
16.
I. Bejarano-Ramirez Jose M. Jurado R. Muñiz-Valencia Á. Alcázar Silvia G. Ceballos-Magaña A. Olivos-Ortiz O. Rangel 《International Journal of Environmental Science and Technology》2017,14(6):1333-1342
The contents of As, Cd, Cu, Cr, Mg, Mn, Ni, Pb and Zn have been determined in sediment and water samples from Valle de las Garzas estuary and Port Manzanillo (Colima, Mexico) using ICP-AES. The concentrations of these elements were used for a comparative study to determine the distribution of heavy metals and to evaluate which elements reflect natural or anthropogenic backgrounds. For this purpose, seven sampling points were selected: Four of them correspond to the lagoon, and three were situated in the port. Statistical analysis of the mineral content was assessed. Initially, data comparison was assessed by statistical tests for each variable. Principal component analysis was then applied considering the influence of all variables at the same time by obtaining the distribution of samples according to their scores in the principal component space. In this way, four studies were carried out: (1) study of sediments collected during the dry season; (2) study of sediments collected during the rainy season; (3) comparative study between sediments from rainy and dry season; and (4) study of water composition collected during rainy season. From the results of the performed analyses, it can be concluded that metals distribution pattern reflected natural and anthropogenic backgrounds (e.g., sediments from the lagoon, situated at the beginning of the rain channel, presented high contents of Zn and Cu, perhaps related to anthropogenic activities or the influence of igneous sediments). 相似文献
17.
《Geoforum》2017
This article advances critical geographies of youth through examining the spatiality implicit in the imagined futures of young women in rural India. Geographers and other scholars of youth have begun to pay more attention to the interplay between young people’s past, present, and imagined futures. Within this emerging body of scholarship the role of the family and peer group in influencing young people’s orientations toward the future remain underexamined. Drawing on eleven months of ethnographic fieldwork, my research focuses on a first generation of college-going young women from socioeconomically marginalized backgrounds in India’s westernmost state of Gujarat. I draw on the “possible selves” theoretical construct in order to deploy a flexible conceptual framework that links imagined post-educational trajectories with motivation to act in the present. In tracing the physical movement of these young women as they navigate and complete college, my analysis highlights the ways in which particular kinds of spaces and spatial arrangements facilitate and limit intra- and inter-generational contact, and the extent to which this affects young women’s conceptions of the future. I conclude by considering the wider implications of my research for ongoing debates surrounding youth transitions, relational geographies of age, and education in the Global South. 相似文献
18.
The shape of sedimentary particles may carry important information on their history. Current approaches to shape classification
(e.g. the Zingg or the Sneed and Folk system) rely on shape indices derived from the measurement of the three principal axes
of the approximating tri-axial ellipsoid. While these systems have undoubtedly proved to be useful tools, their application
inevitably requires tedious and ambiguous measurements, also classification involves the introduction of arbitrarily chosen
constants. Here we propose an alternative classification system based on the (integer) number of static equilibria. The latter
are points of the surface where the pebble is at rest on a horizontal, frictionless support. As opposed to the Zingg system,
our method relies on counting rather than measuring. We show that equilibria typically exist on two well-separated (micro
and macro) scales. Equilibria can be readily counted by simple hand experiments, i.e. the new classification scheme is practically
applicable. Based on statistical results from two different locations we demonstrate that pebbles are well mixed with respect
to the new classes, i.e. the new classification is reliable and stable in that sense. We also show that the Zingg statistics
can be extracted from the new statistics; however, substantial additional information is also available. From the practical
point of view, E-classification is substantially faster than the Zingg method. 相似文献
19.
Hirokazu Fujimaki 《Contributions to Mineralogy and Petrology》1986,94(1):42-45
Concentration ratios of Hf, Zr, and REE between zircon, apatite, and liquid were determined for three igneous compositions: two andesites and a diorite. The concentration ratios of these elements between zircon and corresponding liquid can approximate the partition coefficient. Although the concentration ratios between apatite and andesite groundmass can be considered as partition coefficients, those for the apatite in the diorite may deviate from the partition coefficients. The HREE partition coefficients between zircon and liquid are very large (100 for Er to 500 for Lu), and the Hf partition coefficient is even larger. The REE partition coefficients between apatite and liquid are convex upward, and large (D=10–100), whereas the Hf and Zr partition coefficients are less than 1. The large differences between partition coefficients of Lu and Hf for zircon-liquid and for apatite-liquid are confirmed. These partition coefficients are useful for petrogenetic models involving zircon and apatite. 相似文献
20.
E. M. Prasolov S. A. Sergeev B. V. Belyatsky E. S. Bogomolov K. A. Gruzdov I. N. Kapitonov R. Sh. Krymsky V. O. Khalenev 《Geochemistry International》2018,56(1):46-64
This paper reports the first results of a study of 11 isotope systems (3He/4He, 40Ar/36Ar, 34S/32S, 65Cu/63Cu, 62Ni/60Ni, 87Sr/86Sr, 143Nd/144Nd, 206–208Pb/204Pb, Hf–Nd, U–Pb, and Re–Os) in the rocks and ores of the Cu–Ni–PGE deposits of the Norilsk ore district. Almost all the results were obtained at the Center of Isotopic Research of the Karpinskii All-Russia Research Institute of Geology. The use of a number of independent genetic isotopic signatures and comprehensive isotopic knowledge provided a methodic basis for the interpretation of approximately 5000 isotopic analyses of various elements. The presence of materials from two sources, crust and mantle, was detected in the composition of the rocks and ores. The contribution of the crustal source is especially significant in the paleofluids (gas–liquid microinclusions) of the ore-forming medium. Crustal solutions were probably a transport medium during ore formation. Air argon is dominant in the ores, which indicates a connection between the paleofluids and the atmosphere. This suggests intense groundwater circulation during the crystallization of ore minerals. The age of the rocks and ores of the Norilsk deposits was determined. The stage of orebody formation is restricted to a narrow age interval of 250 ± 10 Ma. An isotopic criterion was proposed for the ore-bearing potential of mafic intrusions in the Norilsk–Taimyr region. It includes several interrelated isotopic ratios of various elements: He, Ar, S, and others. 相似文献