栾川矿集区黄背岭-中鱼库花岗岩中黑云母成分特征及成岩成矿意义

黄背岭-中鱼库钼多金属矿矿区是栾川矿集区目前的重点找矿区域。通过对黄背岭含矿斑状花岗岩与中鱼库隐伏的黑云母二长花岗岩进行岩相学观察与黑云母的化学成分特征分析,探讨了本区的岩石成因及成矿潜力。结果表明黄背岭和中鱼库花岗岩中的黑云母都属于镁质黑云母。黄背岭花岗岩中的黑云母Ti=0.15apfu~0.20apfu,具有退变质与固相线下交代成因的特征,中鱼库花岗岩中的黑云母Ti=0.27apfu~0.35apfu,具有岩浆成因的特征。从岩体浅部到深部,黄背岭岩体结晶压力为93 MPa~14 MPa,结晶深度为3.4km~0.5km。中鱼库岩体结晶压力为145 MPa~58 MPa,结晶深度为5.3km~2.1km。两岩体浅部结晶压力大,深部结晶压力小,表明两者均为快速侵入。两岩体均属壳幔混源的I型花岗岩,是深源中浅成花岗岩。两岩体形成时的温度分别为939.4℃~1 006℃,833℃~966℃,氧逸度分别为10-11.8 MPa~10-10 MPa,10-13.08 MPa~10-10.4 MPa。两者形成时的温度与氧逸度均较高,与其共存的流体都富氟,有利于钼钨多金属矿成矿。综上并结合透岩浆成矿作用的观点,认为本区成矿潜力大。     

赣中城上复式岩体黑云母矿物化学特征及其成岩指示意义

通过对城上复式岩体中黑云母进行详细的岩相学观察和矿物化学成分分析及对黑云母组分的特征及其成岩指示意义的讨论,发现城上花岗岩类中的黑云母均具有富铁贫铝高钛低镁的特征,北部中细粒黑云母花岗闪长岩中的黑云母属镁质黑云母,形成的结晶温度约670℃~710℃,氧逸度10~(-12.4) MPa~10~(-13.2) MPa,成岩压力68 MPa~234MPa,相应的侵位深度为2.6km~8.9km,属Ⅰ型花岗岩,源区物质可能为未经风化的火山岩或少量地壳酸性岩浆和地幔基性岩浆的混合产物;南部大斑中粗粒黑云母二长花岗岩中的黑云母属铁质黑云母,形成的结晶温度约648℃~710℃,氧逸度10~(-14.8) MPa~10~(-16.1) MPa,成岩压力为265 MPa~377 MPa,相应的侵位深度为10.0km~14.2km,而中斑中细粒黑云母二长花岗岩中的黑云母属铁叶云母-铁质黑云母,形成的结晶温度约600℃~645℃,氧逸度10-16.6 MPa~10~(-17.6) MPa,成岩压力为417 MPa~559 MPa,相应的侵位深度为15.8km~21.1km,与他共存的热液流体中相较其他更富氟,均为典型的S型花岗岩,源区物质应是较纯的沉积物质。     

滇西古永地区花岗岩中黑云母成分特征及其成岩成矿意义

滇西古永地区花岗岩与锡矿床在成因上密切相关。黑云母的电子探针分析结果表明,古永黑云母二长花岗岩中的黑云母为铁质黑云母,小龙河锡矿床黑云母似斑状二长花岗岩中的黑云母为铁叶云母。两花岗岩体中黑云母总体显示出富铁(w(TFe O)=22.39%~27.91%)贫镁(w(Mg O)=1.08%~10.51%,含镁系数为0.07~0.50)的特征;但两岩体花岗岩中黑云母的化学成分具有明显的差异,古永花岗岩体中黑云母表现出相对富镁,为含幔源物质混入的I型花岗岩;而小龙河成矿花岗岩体中黑云母相对富铝贫镁,为典型壳源过铝质的S型花岗岩。古永花岗岩体和小龙河花岗岩体中黑云母的结晶温度分别为700~750℃、620~650℃,氧逸度(lgf(O2))分别为-14.0~-13.8、-17.5~-17.2。古永岩体花岗岩中黑云母结晶压力为67~120 MPa,结晶深度为2.54~4.55 km。表明本区花岗岩形成于相对高温、低氧逸度、较浅的环境。相对于古永花岗岩体,小龙河花岗岩体具有更大的Sn成矿潜力,更有利于本区锡矿床的形成。     

东秦岭钼矿带南泥湖-上房沟花岗斑岩成因及其对钼成矿作用的制约

河南省栾川县南泥湖-上房沟斑岩-矽卡岩型钼(钨)矿田是我国最重要的钼矿产区,钼矿探明储量(金属量)达205万吨.区内钼成矿与南泥湖和上房沟两个花岗斑岩小岩体关系密切,两岩体产于华北克拉通南缘,岩石为高硅、富碱和较高分异指数的碱性-碱钙性、过铝质花岗岩.其微量元素地球化学组成具有显著亏损Eu、Sr、Ba、Ti的特征,表明岩浆经历过相当高程度的分异演化.较低的ε_(Nd)(t)值(-12.7～-15.5)和年轻的Nd模式年龄(1.48～1.71Ga)表明其成岩物质来源主要为年轻的地壳物质.南泥湖和上房沟岩体的锆石LA-ICPMS U-Pb年龄分别为149.56±0.36Ma(MSWD=1.5)和135.38±0.29Ma(MSWD=1.4).结合现有的秦岭一大别造山带中生代花岗岩类的有关地球化学研究成果,东秦岭钼成矿带内的燕山期成矿花岗岩小岩体及大岩基应为扬子克拉通北缘中生代向华北克拉通A型俯冲的地壳物质在碰撞后伸展构造环境下部分熔融的产物并可能有部分地幔物质的参与.成矿小岩体是花岗岩大岩基高度分异演化的结果,花岗岩大岩基结晶分异导致其中挥发分的过饱和、挥发分对正在固结的岩浆体中成矿元素的淋滤是小岩体成矿的关键.     

栾川西鱼库隐伏斑岩型Mo-W矿床地球化学及其意义

西鱼库大型隐伏斑岩钼-钨矿床是近年来在栾川地区开展深部找矿勘查过程中的新发现。该矿床与南泥湖、上房沟钼矿不同,其矿体主要赋存于斑岩体内部而非岩体外接触带的矽卡岩或角岩中。与南泥湖和上房岩体相比,西鱼库隐伏斑岩体的Si O2、K2O含量略低,具有正Eu异常,表明西鱼库隐伏斑岩体比南泥湖和上房岩体分异程度略低,更接近成矿岩浆中心位置。     

新疆尾亚—天湖地区花岗岩类剥蚀程度估算及对区域找矿的启示

尾亚—天湖地区位于新疆中亚造山带东南部的中天山地块内,晚古生代—中生代岩浆活动强烈,产出了战略性关键矿产尾亚钒铁磁铁矿。在详细岩相学观察的基础上,对尾亚、天湖和沙泉子南岩体中的角闪石和黑云母进行了电子探针(EMPA)测试分析,限定了3个岩体结晶的温压条件、氧逸度、含水量和含铁指数等要素,为解析中天山地块的岩浆-成矿物化条件及其区域找矿勘查工作提供参考。测试结果表明,该区花岗岩类中的角闪石富镁、钙、钠,贫钾,属于钙角闪石族;黑云母有高镁、钛、铝、钾和低硅、钠的特征为镁质黑云母。角闪石和黑云母的化学成分揭示其寄主岩浆为钙碱性造山带岩系,具有壳幔混源的特征,推测可能是板块俯冲背景下由地幔楔与大陆地壳物质混熔形成。根据角闪石-黑云母矿物温压计,估算出沙泉子南石英闪长岩的结晶温度为651~753 ℃,压力为31~79 MPa,尾亚二长花岗岩和钾长花岗岩的结晶温度为762~833 ℃,压力为85~215 MPa,天湖花岗闪长岩的结晶温度为668~812 ℃,压力为31~117 MPa。3个岩体岩浆结晶时的氧逸度lgf(O₂)范围为-15.7~-9.4,而且在角闪石结晶时岩浆具有较高的含水量。综合分析,认为该区的花岗岩类具有高温、低压、高氧逸度、富水和高含铁指数的特点,有利于Fe等成矿元素在流体中富集,具有良好的铁矿成矿条件。进一步利用角闪石-黑云母压力计,计算了花岗岩类岩体的侵位深度,从而估算出岩体的剥蚀程度处于2.2~5.5 km,且区域的隆升剥蚀量差异明显;结合现有的矿产地表展布特征,推测天湖岩体一带深部仍具有较好的铁矿找矿潜力。     

秦岭造山带光头山岩体群黑云母地球化学特征及成岩意义

针对南秦岭光头山岩体群的岩相学和黑云母地球化学分析,进而对秦岭造山带晚三叠世花岗岩形成的温度、压力和氧逸度等物理化学条件进行专门的研究。其中岩相学观察表明,光头山岩体群主要由黑云母二长花岗岩和花岗闪长岩组成。电子探针分析结果表明黑云母二长岗岩中的黑云母是铁质黑云母,花岗闪长岩中的黑云母是镁质黑云母,所测黑云母的Fe2+/(Fe2++Mg)比值变化范围较小,表明其未受到后期改造,为原生黑云母,可以用来估算岩体的成岩物理化学条件。根据黑云母地球化学成分计算的成岩温度为(645~710)℃,压力为(126~309)MPa,logfo2为-12~-15,岩体侵位于中上地壳层次(约8.6km)。黑云母地球化学分析还表明,光头山岩体群主要为过铝质-造山带钙碱性花岗岩,岩浆以壳源为主兼具壳幔混源的特征。     

桂东北姑婆山岩体矿物学和年代学特征及其成岩成矿意义

为揭示桂东北姑婆山一带花岗岩的成岩成矿特征，本文对姑婆山岩体进行了黑云母矿物化学成分分析和锆石U-Pb年代学研究。花岗岩中黑云母化学成分分析结果表明：黑云母具有富铁镁、贫钙钠的特征，w（TFeO）为26.78%~31.06%、w（MgO）为2.98%~6.60%，且w（TFeO）与w（MgO）呈明显的负相关性，说明其结晶过程中主要发生了Fe²⁺←→Mg²⁺的置换反应；黑云母的含铁指数为0.68~0.84，属于高铁黑云母，氧逸度为-17.0~-15.5，结晶温度为680~705℃，平均为695℃；黑云母的全铝压力计显示黑云母结晶的压力为69~179 MPa，平均为115 MPa，对应的侵位深度相当于2 621~6 755 m，平均深度为4 331 m。年代学分析结果显示，采自姑婆山岩体的两个代表性花岗岩样品形成年龄分别为（162±3）和（163±2）Ma，为燕山早期，与华南中生代大规模岩浆-成矿作用时代一致。综合上述分析，姑婆山岩体形成于较高温度、低氧逸度、较浅的环境，显示出良好的锡成矿性，具有良好的找矿前景。     

上黑龙江盆地二十一站岩体角闪石和黑云母成分特征及成岩成矿意义

二十一站岩体位于黑龙江省东北部大兴安岭地区塔河县境内,该岩体产出的岩石类型包括早白垩世二长岩和石英二长斑岩及早侏罗世花岗岩和二长岩等,在该岩体中已发现斑岩型铜金矿床,但是该岩体形成的物理化学条件和岩石成因尚不清楚,不同岩性岩浆岩的成矿潜力也不明确。鉴于此,本文以二十一站岩体中不同时代的花岗岩、二长岩、石英二长斑岩的黑云母和角闪石为研究对象,结合偏光显微镜、电子探针背散射图像和电子探针化学成分,对该岩体的岩石学、矿物学特征进行了研究,并对岩浆结晶的物理化学条件、岩石成因和成矿意义进行了探讨。结果显示:早白垩世二长岩中角闪石化学成分显示:角闪石富钙(CaO 11.21%~11.78%)、富镁(MgO 13.61%~14.85%)、贫钠(Na2O 0.80%~1.11%)和贫钾(K2O 0.40%~0.54%),属于镁角闪石,结晶温度为704.92~805.58℃,平均温度为761.82℃,压力为73.83~115.93MPa,对应岩浆侵位深度为2.8~4.4km,结晶时岩浆氧逸度为△NNO+1.63,含水量为H2O=4.92%,反映出岩浆结晶时高温、高氧逸度、富含水分、浅侵位的特征。黑云母的Fe2+/(Fe2++Mg)比值比较均一,反映黑云母未遭受后期流体改造,均为原生岩浆成因的黑云母。其中早侏罗世花岗岩和二长岩所代表的A类黑云母化学成分上富铁(TFeO 19.92%~22.42%)贫镁(MgO 7.99%~10.46%),属于铁质黑云母,早白垩世二长岩和石英二长斑岩所代表的B类黑云母相比于A类黑云母更富镁(MgO 12.38%~14.45%)和钛(TiO21.90%~2.75%),贫铁(TFeO 16.64%~17.97%)和铝(Al2O315.00%~16%.79),属于镁质黑云母。A类和B类黑云母对应岩浆结晶温度分别为720~740℃和750~780℃;压力为202.20~443.49MPa和158~231MPa,对应岩浆侵位深度为6.67~14.64km和5.24~7.24km;结晶时岩浆氧逸度分别为10-15~10-16和10-12~10-13;岩浆来源为壳源,且B类黑云母对应岩浆有地幔物质参与。因此,可以认为二十一站岩体中早白垩世二长岩和石英二长斑岩具有中高温,高氧逸度应含水量,岩浆主要来源于地壳物质的部分熔融,并有部分地幔物质参与,侵位深度较浅的特点,具有形成大型斑岩矿床的潜力。早侏罗世花岗岩和二长岩氧逸度相对较低,侵位较深,物质来源为地壳,因此不具备成矿潜力。     

诸广棉花坑铀矿床花岗岩中黑云母成分特征及其成岩成矿意义

诸广棉花坑铀矿床围岩是中粒斑状二云母花岗岩和中粗粒斑状黑云母花岗岩,本文通过对其中的黑云母进行了岩相学观察和详细的矿物化学分析以探讨黑云母的形成条件及其成岩成矿意义。电子探针分析结果表明,本区黑云母富铁贫镁,属于铁叶黑云母,指示诸广花岗岩体为过铝质岩系,起源于地壳。黑云母结晶的温度为650~700℃,logfO2为-15~-16,压力为159~247MPa,对应的侵位深度为5.2~7.2km。与非产铀花岗岩对比,本区岩浆具有相对较低的温度和氧逸度。     

Roles of xenomelts,xenoliths, xenocrysts,xenovolatiles, residues,and skarns in the genesis,transport, and localization of magmatic Fe-Ni-Cu-PGE sulfides and chromite

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.     

Mountains,nations, parks,and conservation

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.     

Parents,permission, and possibility: Young women,college, and imagined futures in Gujarat,India

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.     

Coprecipitation of Ti,Mo, Sn and Sb with fluorides and application to determination of B,Ti, Zr,Nb, Mo,Sn, Sb,Hf and Ta by ICP-MS

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.     

Models,validation, and applied geochemistry: Issues in science,communication, and philosophy

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.     

Comparative study of As,Cd, Cu,Cr, Mg,Mn, Ni,Pb and Zn concentrations between sediment and water from estuary and port

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).     

Pebbles,Shapes, and Equilibria

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.     

Partition coefficients of Hf,Zr, and REE between zircon,apatite, and liquid

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.     

Isotopic systematics of He,Ar, S,Cu, Ni,Re, Os,Pb, U,Sm, Nd,Rb, Sr,Lu, and Hf in the rocks and ores of the Norilsk deposits

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.