新疆黄山铜镍硫化物矿床成矿岩浆作用过程

黄山铜镍硫化物矿床镁铁．超镁铁质岩体岩相发育良好,主要包括橄榄岩、辉石岩、辉长岩和闪长岩,橄榄岩中部分橄榄石包含有硫化物珠滴。对该岩体不同岩相进行了主元素、微量元素、铂族元素和单矿物的分析,结果表明,不同类型岩石的化学组成受橄榄石、辉石和斜长石结晶分异作用的控制。微量元素和稀土元素具有相似的分布模式,（La／Yb）N介于1．14—3．65之间,明显亏损Nb和Ta,富集Sr。含矿岩石Cu／Pd和Ti／Pd比值大于原生地幔岩浆。上述结果揭示黄山镁铁-超镁铁质岩体不同岩性的岩石具有不同的主元素和微量元素特征,但母岩浆来自同一源区。根据橄榄石的F0值和全岩的主要氧化物组成估算出母岩浆为高镁（MgO约为15％）玄武岩岩浆,在岩浆作用过程中地壳富硅组分的混染是导致硫化物熔离的主要机制。     

岩浆铜镍矿与钒钛磁铁矿的过渡类型--新疆哈密香山西矿床

铜镍硫化物矿床与钒钛磁铁矿矿床虽然同属与镁铁-超镁铁质岩有关的岩浆型矿床范畴,但在一般情况下,二者是不共生的.新疆东天山地区的香山西矿床则是一个铜镍矿与钛铁矿共生的实例.香山地区为一复式含矿杂岩体,最早期形成辉长岩(如角闪辉长岩、灰白色细粒辉长岩等)为主体的侵入;第二期侵入的是以辉橄岩、单辉橄榄岩、二辉橄榄岩等为主的超镁铁质岩,含铜镍硫化物矿化;第三期则为岩浆期后残余岩浆形成的含钛铁矿化的辉长岩(脉).香山西铜镍-钛铁矿床含矿岩石的碱度、镁铁指数、岩浆酸度、钙碱富集指数等地球化学参数,氧逸度和硫逸度等物理化学参数均介于独立的典型铜镍硫化物和典型钒钛磁铁矿矿床之间.矿床中磁铁矿较其他钒钛磁铁矿矿床(尾亚)具较高的V和Ti含量,同时黄铁矿和黄铜矿具较高的Co、Ni和Cu含量,反映出成矿过程中,Cu-Ni-Co系列与V-Ti-Fe系列的分离不够彻底.形成本区CuNi-VTi复合型矿床的原因,可能在于矿床所处独特的构造环境--产于造山带,而不是克拉通(边缘).     

天山-兴蒙成矿域岩浆铜镍硫化物矿床地质特征和成矿动力学背景

天山-兴蒙成矿域是中亚成矿域的重要组成部分,中亚造山带演化过程中,形成了大量的镁铁-超镁铁岩石和岩浆铜镍硫化物矿床,自西向东主要有菁布拉克、喀拉通克、黄山东和红旗岭等岩浆铜镍硫化物矿床,构成重要内生金属矿床富集区.含矿镁铁-超镁铁岩带成岩成矿时代由西至东逐渐变新,暗示古亚洲洋盆由西向东剪刀式构造迁移过程,其岩浆作用记录了中亚造山带构造演化过程.     

红旗岭―茶尖岭矿带部分含矿岩体时代认识——从陆壳、岩石圈角度认识含矿镁铁-超镁铁质岩体时代

红旗岭―茶尖岭矿带发育镁铁-超镁铁岩体(岩墙群)及铜镍硫化物矿床。关于该矿带含矿岩体时代的观点包括华力西期和印支期。含铜镍硫化物矿床的镁铁-超镁铁岩体(岩墙群)发育要件:初始成熟陆壳、较薄的岩石圈、拉张应力背景,三者缺一不可。只有符合地质事实、符合矿带含铜镍矿镁铁-超镁铁岩体(岩墙群)发育要件的同位素定年数据,才能代表含矿岩体的成岩成矿时代。红旗岭—茶尖岭矿带印支期不具备含矿镁铁-超镁铁岩体(岩墙群)产出的要件。华力西期350Ma,矿带具备红旗岭1号、7号含中、大型铜镍硫化物矿床的镁铁-超镁铁岩体产出的要件,理应代表1号、7号岩体时代;华力西期258Ma,矿带具备茶尖岭包括1号、6号、新6号等含小型铜镍硫化物矿床的镁铁-超镁铁质岩体产出的要件,均代表茶尖岭矿区的镁铁-超镁铁岩体的时代。     

黄山东镁铁-超镁铁侵入杂岩中橄榄石深部结晶作用的发现

近年来,在新疆哈密黄山地区发现了一系列与铜镍硫化物矿床有关的镁铁超-镁铁侵入杂岩,构成了黄山铜镍成矿带。黄山东镁铁-超镁铁侵入杂岩为该成矿带重点岩体之一,其主要造岩矿物橄榄石深部结晶作用的发现对于丰富岩浆的成因理论、确切地解释杂岩体成岩成矿过程中岩浆的分异演化和成矿带内其它杂岩橄榄石深部结晶作用的确定均有重要意义。     

新疆坡一含铜镍矿镁铁-超镁铁质岩体岩浆作用深部过程及形成机制探讨

<正>新疆东天山-北山是中亚造山带南缘镁铁-超镁铁岩体的集中分布区,因其赋含铜镍硫化物矿床而得到地质学家的广泛关注,并逐渐成为我国继世界第三大甘肃省金川岩浆铜镍硫化物矿床之后的,又一重要岩浆铜镍硫化物矿床的主要产地和热点地区。东天山地区的多数镁铁-超镁铁岩体赋含铜镍矿并已在开采中(如香山、黄山东、黄山、图拉尔根、天宇等)或被认定为具有赋存     

红旗岭镁铁-超镁铁岩侵入体及铜镍硫化物矿床的成岩成矿机制

红旗岭铜镍矿床地处华北地台与吉黑地槽系接触带--辉发河断裂北侧.区内出露30多个镁铁-超镁铁质岩体,其中1、7号超镁铁岩体中赋存铜镍硫化物矿(床)体.含矿岩体分相明显,各类岩石均具堆积结构.铜镍矿体呈似板状、脉状、透镜状及囊状赋存于超镁铁岩体底部橄榄辉岩相中.岩石学和地球化学研究表明,7号岩体形成以流动分异为主,1号岩体为重力分异;原始岩浆属拉斑玄武质,块状矿石系压滤作用产物,后续岩浆的补给和混合补充了成矿物质,硫化物不混溶程度受挥发分制约,矿床属岩浆深部熔离分异成因,成矿时代为印支期.     

东天山黄山南镁铁-超镁铁岩体的岩浆演化过程:矿物学、Sr-Nd同位素特征的指示

黄山南镁铁-超镁铁质岩体位于东天山造山带觉罗塔格构造带内,属于土墩-黄山-图拉尔根镁铁-超镁铁质岩带。本文在前人研究的基础上,从橄榄石、辉石矿物学组成和全岩Sr、Nd同位素等方面对黄山南岩体进行了分析研究,并与黄山、黄山东、香山等典型含矿岩体作了对比,旨在进一步查明黄山南岩体的岩浆源区和母岩浆性质及其岩浆演化过程。Sr-Nd同位素特征表明黄山南岩体来自一个弱亏损的地幔源区,相较黄山、黄山东、香山等岩体的源区具有更加富集的特征。黄山南岩体中的橄榄石属于贵橄榄石,斜方辉石主要为古铜辉石,少数为紫苏辉石,单斜辉石主要为顽透辉石、普通辉石和少数的透辉石。单斜辉石和橄榄石的成分特征表明形成黄山南岩体的母岩浆为演化程度较低的拉斑玄武质岩浆,且母岩浆成分具有高Mg、高Ni的特点。计算得到黄山南岩体母岩浆的Fe O~T=13.20%、MgO=16.96%、Ni=377.2×10~(-6),且母岩浆在结晶分异过程中没有经历充分的硫化物熔离作用,这也是造成母岩浆中Ni含量较高以及岩体含矿性较差的主要因素。     

东天山二叠纪镁铁-超镁铁质成矿岩体造岩矿物特征及其成因意义

东天山造山带与镁铁-超镁铁质岩体有关的铜镍硫化物矿床数量多,分布集中,是我国重要的铜镍成矿带之一。成矿岩体多以小岩体群形式产出,由西向东分布有白鑫滩、黄山和图拉尔根3个岩体群,大型矿床主要赋存在黄山岩体群内。本文对3个岩体群内成矿岩体的主要造岩矿物进行了系统的对比研究。成矿岩体的主要造岩矿物为贵橄榄石、古铜辉石、单斜辉石、斜长石和角闪石以及少量的铬尖晶石和金云母。橄榄石Al温度计计算结果表明,黄山岩体群内成矿岩体的母岩浆结晶温度介于1 143~1 257℃之间,略低于白鑫滩和图拉尔根岩体群(1 283~1 301℃)。单斜辉石压力计算表明成矿岩体的结晶压力相似,介于0.31~0.33 GPa之间。成矿岩体中均富含含水矿物,且单斜辉石结晶早于斜长石,指示成矿岩体的原始岩浆形成于富水环境。成矿岩体的单斜辉石具有较高的Al/Ti值,铬尖晶石和橄榄石具有与岛弧火山岩相似的矿物学特征,结合区域构造演化,认为东天山镁铁-超镁铁质成矿岩体的原始岩浆是被消减板片交代过的地幔部分熔融的产物。矿物学特征对比显示了黄山岩体群内成矿岩体更富斜方辉石和中性斜长石,且具有较低的铬尖晶石Cr~#值和橄榄石Ca含量。结合前人研究成果和相关地球化学数据,认为相对高的混染程度导致了黄山岩体群的母岩浆富SiO_2和Al_2O_3,同时降低了岩浆的结晶温度。     

四川力马河镁铁-超镁铁质岩体的地球化学特征及成岩成矿分析

四川会理力马河镍矿是峨眉山大火成岩省最重要的岩浆硫化物矿床之一,成矿岩体为一小型锾铁-超镁铁岩侵入体,由含斜长石的超镁铁岩(包括舍长辉石橄榄岩和斜长橄榄辉石岩)和辉长岩类的镬铁质岩组成.矿床富含硫化物,成矿元素组合为铜、镍,铂族元素含量很低,没有铂族元素的工业富集,是蛾眉山大火成岩省中富铜镍贫铂族元素的代表性岩浆硫化物矿床.本文对力马河镍矿成矿岩体的镁铁、超镁铁岩及矿床中各种硫化物矿石进行了主量元素、微量元素及铂族元素含量分析.分析结果表明,力马河岩体的镁铁、超镁铁岩属拉斑玄武岩成因系列,岩石特征微量元素比值大致与高钛的峨眉山玄武岩相当、与低钛的峨眉山玄武岩有明显区分,但估计原始岩浆强不相容微量元素绝对含量大大低于高钛玄武岩,因此,其成矿岩体不是与一般的低钛或高钛峨眉山玄武岩(不包括苦橄岩在内)直接对应的深成相.岩体超镁铁岩及矿石铂族元素组成特征表现为无钌亏损的型式,钯/铱比值较小、在5左右,也显著不同于一般的峨眉山玄武岩,而类似于峨眉山大火成岩省苦橄岩的铂族元素组成.运用岩石地球化学研究方法计算,原始岩浆为苦橄质成分:MgO含量约17%、SiO2含量约48%.估计原始岩浆形成于130公里左右的深度,由类似于洋岛玄武岩岩浆源区成分的地幔经19%左右的部分熔融形成.超镁铁岩及硫化物矿石铂族元素含量一般在10-9～10-8暑级,铂族元素相对铜镍强烈亏损,铜/钯比值高于原始地幔10～100倍,铜镍铂族元素组成的原始地幔标准化曲线呈铂族元素显著亏损的“U“型.模式分析说明,导致铂族元素亏损的原因是岩浆成矿演化过程中多阶段硫化物熔离作用造成的,早期熔离出来的硫化物被丢失并造成岩浆中铂族元素亏损,其铂族元素亏损后的岩浆(第)二次硫化物熔离富集形成铂族元素亏损的矿石.     

The Permian Huangshanxi Cu–Ni deposit in western China: intrusive–extrusive association,ore genesis,and exploration implications

The Permian Huangshanxi Cu–Ni deposit is the second largest magmatic sulfide deposit discovered to date in a major Ni–Cu province related to protracted basaltic magmatism in eastern Xinjiang, China. It is hosted by a small mafic–ultramafic intrusion comprised predominantly of lherzolites, olivine websterites, gabbronorites, and gabbros. The Huangshanxi intrusion is coeval with Permian basalts of tholeiitic and alkaline affinities in the Tuha and Tarim basins, respectively. To evaluate a possible genetic relationship between the Huangshanxi intrusion and a specific type of coeval basalt in the region, as well as ore genesis in the intrusion, we have carried out an integrated mineralogical, petrological, and geochemical study. Our data reveal that the Huangshanxi intrusive rocks are characterized by relatively flat chondrite-normalized REE patterns, depletion in Nb and Ta, and elevated εNd values varying between 6 and 10. These features are similar to those of coeval tholeiitic basalts in the nearby Tuha basin, but are significantly different from those of coeval alkaline basalts in the relatively remote Tarim basin. The geochemical similarities and differences suggest that the Huangshanxi intrusion is genetically related to the tholeiitic basalts in the Tuha basin, not to the alkaline basalts in the Tarim basin, as suggested previously by some researchers. This implies that regional exploration for the Huangshanxi-type Cu–Ni deposits should be centered in the Tuha basin instead of the Tarim basin. More specifically, the uplifted areas around the Tuha basin where similar intrusions may have been brought close to the surface should be carefully examined for mineralization potential. Intrusive relations and mass balance constraints from incompatible trace elements and sulfide abundances suggest that the Huangshanxi intrusion represents a dynamic magma conduit through which multiple pulses of magma ascended to higher levels or to the surface. Numerical simulation of magma evolution and mixing calculations using Sr–Nd isotopes indicate that selective assimilation of S-bearing crustal materials is important for sulfide saturation during the early stages of magma evolution when lherzolites formed. Fractional crystallization may have also played a role in the attainment of sulfide saturation during the later stages of magma evolution when olivine websterites and gabbronorites formed. In both cases, immiscible sulfide droplets were retained in the conduit to form disseminated sulfide lenses while the fractionated silicate liquids and buoyant phases such as plagioclase continued to ascend. Extremely low PGE tenors in the sulfide ores of the Huangshanxi deposit suggest that the parental magma was highly depleted in chalcophile elements possibly due to previous sulfide segregation at depth.     

东昆仑石头坑德镁铁-超镁铁质岩体矿物学特征及成矿指示

石头坑德镁铁-超镁铁质岩体位于东昆仑造山带东段五龙沟地区,邻近昆中大断裂,主要岩性为辉石岩、橄辉岩、橄榄岩、辉长岩等,铜镍矿体主要赋存于Ⅰ号岩体的辉石岩、橄辉岩和橄榄岩中。岩石地球化学特征表明,其镁铁比值(m/f)变化范围在2.77~6.01之间,属铁质系列的镁铁-超镁铁岩,有利于成铜镍矿。稀土总量总体较低,轻稀土元素之间分馏强,重稀土元素之间分馏弱。岩石总体富集LILE(Rb、Ba、Th、U),贫HFSE(Nb、Ta、Zr、Y),具有明显的Rb、U正异常及Nb、Ta的负异常。超镁铁岩类橄榄石中的Ni普遍亏损,指示深部存在硫化物的熔离作用,在橄榄石结晶之前,大量的Ni进入到硫化物中,极有利于形成富矿岩浆或矿浆。可见,伴随同化混染作用的发生,岩浆中S达到过饱和,进而硫化物发生不混溶作用,富含硫化物的岩浆运移至东昆仑造山带邻近昆中断裂构造薄弱的部位成岩成矿。铜镍矿体多赋存在含橄榄石的超镁铁质岩体内,指示石头坑德岩体深部存在高度富集铜镍的部位,是下一步的找矿方向。     

东昆仑志留纪辉长岩地球化学特征及与铜镍成矿关系探讨

东昆仑造山带新发现的夏日哈木超大型岩浆铜镍矿床、石头坑德大型岩浆铜镍矿床及冰沟南小型岩浆铜镍矿床,其矿体均赋存于橄榄辉石岩内,而辉长岩又是该含矿橄榄辉石岩的直接围岩,并且辉长岩的形成时代相近(夏日哈木辉长岩431Ma、石头坑德辉长岩425Ma、冰沟南辉长岩427Ma),产出位置属于同一大的构造单元,均邻近昆北及昆中断裂。通过对辉长岩的地球化学特征研究,发现明显富集轻稀土元素和明显的Nb-Ta负异常,亏损高场强元素。Sr-Nd同位素研究,表明东昆仑夏日哈木和石头坑德辉长岩岩体的母岩浆来自一个曾经被交代富集的地幔源区,可能揭示了由于从洋壳释放出的流体交代地幔楔的岩石成因。结合区域构造演化和辉长岩形成时代,认为东昆仑夏日哈木和石头坑德辉长岩形成于碰撞后伸展环境。辉长岩岩浆源区性质与赋矿辉石岩存在明显不同,并非同一岩浆活动的产物。辉长岩在东昆仑造山带地区直接充当了含矿辉石岩的直接围岩,与岩浆铜镍硫化物矿体的形成没有关系,富含橄榄石的超镁铁质岩石更有利于形成具有较大经济价值的铜镍矿体。这为指导东昆仑找矿实践和岩浆铜镍矿床成矿理论研究提供了基础。     

东天山香山铜镍-钛铁成矿与两类岩浆演化关系探讨

香山矿床是东天山唯一一个铜镍矿体与钛铁矿体共存的复合型矿床,目前普遍被认为是同源岩浆高度演化的产物。但为何区内众多同时代镁铁-超镁铁质岩体中只有香山岩体产出有大型钛铁矿床?这一问题仍有待进一步探讨。本文通过系统对比香山与其相邻的黄山东、黄山和黄山南等典型铜镍矿的地球化学特征、母岩浆性质及岩浆演化过程,认为香山岩体母岩浆相对其相邻典型铜镍矿床并不富集Fe和Ti,且其母岩浆早期演化过程及分异演化程度相似。模拟计算表明:岩浆体系早期都处于较还原的环境(f_(O_2)QFM+1),而且都发生了大量橄榄石、斜方辉石和单斜辉石的分离结晶和硫化物的熔离,由此消耗了岩浆体系中大量的Fe,导致残余岩浆中Fe含量降低;另外在岩浆演化的各阶段,尤其到岩浆演化后期,大量角闪石的结晶进一步降低了残余岩浆中的Fe和Ti的含量,不能造成Fe和Ti的逐渐富集,据此我们认为同源岩浆演化不具备形成钛铁矿床的物质基础。通过初步对比东天山地区典型铜镍矿床和钛铁矿床与该地区早二叠世两类玄武岩的地球化学特征及演化趋势,我们初步推测东天山地区铜镍成矿与钛铁成矿是两类不同性质岩浆独立演化的产物,铜镍成矿可能与拉斑玄武质岩浆演化密切相关,而钛铁矿则可能与碱性玄武岩演化密切相关。     

吉林红旗岭1号和7号岩体中含矿超镁铁质岩的矿物化学特征:对岩浆演化过程以及铜镍硫化物矿床形成机制的约束

本文对吉林红旗岭1号和7号岩体中含矿超镁铁质岩的主要造岩矿物进行了详细研究。两岩体的主要造岩矿物为贵橄榄石、古铜辉石、单斜辉石、斜长石、角闪石和金云母。岩浆的暗色矿物结晶顺序为:橄榄石→斜方辉石→单斜辉石→角闪石→黑云母,与镜下实际观察一致,是岩浆在不同深度结晶的产物。原始岩浆来自上地幔,两岩体进入高位岩浆房中的熔体的MgO含量分别13.98%和14.22%、Mg#值分别为72.22和71.05,为含水的高镁的苦橄质玄武岩浆。深部岩浆房深度距地表约26～27km,岩浆房内的结晶温度介于1280～1379℃之间,即结晶于下地壳中。岩浆由深部上升到高位(浅部)岩浆房中的过程是近绝热的,也是快速完成的。岩浆可能经历了两次岩浆房的演化过程,岩浆在上升到高位岩浆房之前,在深部曾经历了较短时间的橄榄石和少量辉石的分离结晶作用;但在高位岩浆房中混染了地壳物质,与此同时,还经历了同源岩浆混合作用以及岩浆过冷却作用,这些都有利于岩浆体系中成矿元素含量增高以及硫达到饱和状态,使金属硫化物熔离并晶出,从而使岩体发生铜镍矿化作用。     

http://www.sciencedirect.com/science/article/pii/S1674987111000429

The three most crucial factors for the formation of large and super-large magmatic sulfide deposits are: (1) a large volume of mantle-derived mafic-ultramafic magmas that participated in the formation of the deposits; (2) fractional crystallization and crustal contamination, particularly the input of sulfur from crustal rocks, resulting in sulfide immiscibility and segregation; and (3) the timing of sulfide concentration in the intrusion. The super-large magmatic Ni-Cu sulfide deposits around the world have been found in small mafic-ultramafic intrusions, except for the Sudbury deposit. Studies in the past decade indicated that the intrusions hosting large and super-large magmatic sulfide deposits occur in magma conduits, such as those in China, including Jinchuan (Gansu), Yangliuping (Sichuan), Kalatongke (Xinjiang), and Hongqiling (Jilin). Magma conduits as open magma systems provide a perfect environment for extensive concentration of immiscible sulfide melts, which have been found to occur along deep regional faults. The origin of many mantle-derived magmas is closely associated with mantle plumes, intracontinental rifts, or post-collisional extension. Although it has been confirmed that sulfide immiscibility results from crustal contamination, grades of sulfide ores are also related to the nature of the parental magmas, the ratio between silicate magma and immiscible sulfide melt, the reaction between the sulfide melts and newly injected silicate magmas, and fractionation of the sulfide melt. The field relationships of the ore-bearing intrusion and the sulfide ore body are controlled by the geological features of the wall rocks. In this paper, we attempt to demonstrate the general characteristics, formation mechanism,tectonic settings, and indicators of magmatic sulfide deposits occurring in magmatic conduits which would provide guidelines for further exploration.     

寄主岩浆硫化物和氧化物矿床的镁铁质-超镁铁质岩体对比分析与成矿过程评述

镁铁质-超镁铁质岩体是世界上岩浆硫化物(Ni-Cu-PGE)和氧化物(Fe-Ti-V-P)矿床的主要载体.全球主要岩浆硫化物和氧化物矿床均可以产于大火成岩省、克拉通区的裂谷带或伸展环境、褶皱带内的后碰撞伸展环境.寄主岩浆硫化物矿床的岩体规模相差甚大(从6×104km2到＜0.1km2),既有超镁铁质岩石组合也有镁铁质岩石组合,但其原生岩浆主要为拉斑玄武质岩浆.含镍铜的铂族元素矿床主要赋存于规模很大的层状岩体中,而镍铜硫化物矿床主要赋存于小岩体中.寄主钒钛磁铁矿或磁铁矿矿床的岩体主要是以辉长岩为主的层状杂岩体.寄主钛铁矿-磷灰石矿床的岩体均为层状的斜长岩-纹长二长岩-紫苏花岗岩岩体.尽管其岩石组合相差很大,但其原生岩浆均属拉斑玄武质.寄主硫化物矿床的岩体相对富Si、Mg、Cr、Ni,而寄主氧化物矿床的岩体相对富Fe-Ti-P-V,造岩矿物晶体化学也反映了这种差异.对全球主要含矿岩体的对比分析表明,导致这种反差的主要控制因素应该是岩浆生成时的压力状态,源区性质和熔融程度的差异可能只在局部范围内起作用.对岩浆硫化物矿床成矿过程的认识集中体现在金川模式和岩浆通道模式上,对岩浆氧化物矿床成矿过程的认识体现在氧化物和磷灰石是堆晶相还是从不混溶的矿浆中结晶的.对比分析表明,成矿过程具有多样性,试图用一种模式概括所有同类矿床成矿过程的想法未必可取.毫无疑问,适宜的氧化还原环境是形成岩浆矿床的必要务件,伴随岩浆演化及成矿过程的氧速度变化及其诱因问题尚待进一步探索.     

吉林红旗岭地区含矿与不含矿岩体的地质地球化学对比

吉林红旗岭地区是我国岩浆型铜镍硫化物矿床的主要矿化集中区之一。在区内已发现的镁铁质一超镁铁质岩体中，有的含有铜镍矿床或铜镍矿化，有的则不含矿。通过本区含矿与不含矿岩体的形成时代、岩石组合、橄榄石矿物成分、岩石化学成分和微量元素组合特征的对比，建立起镁铁质-超镁铁质岩体含镍性的评价标志，为隐伏岩体和新发现岩体含矿性的评价提供了理论依据。     

Comparisons among the Oortsog,Dulaan, and Nomgon mafic-ultramafic intrusions in central Mongolia and Ni-Cu deposits in NW China: implications for economic Ni-Cu-PGE ore exploration in central Mongolia

Although there are many mafic-ultramafic intrusions in the western and central regions of Mongolia, Central Asian Orogenic Belt (CAOB), no economic-grade Ni-Cu deposits have yet been discovered. To understand the economic Ni-Cu deposit potential of the intrusions in central Mongolia, the parental magma affinity and sulfide saturation of the Oortsog, Dulaan, and Nomgon Ni-Cu mineralized mafic-ultramafic intrusions are studied. These three intrusions are predominantly gabbroic in composition, while the Oortsog and Dulaan intrusions also contain small proportions of peridotites. The parental magmas of the Oortsog and Dulaan intrusions are tholeiitic, as indicated by their Cr-spinel and clinopyroxene compositions, whereas the parental magma of the Nomgon intrusions is likely calc-alkaline. The compositions of Cr-spinel and clinopyroxene, combined with the presence of significant Nb-Ta depletions, indicate that these rocks were most likely derived from modified mantle sources. Both the Oortsog and Nomgon intrusions form two clusters in terms of their olivine composition, suggesting that multiple magma surges were involved during their emplacement. The relatively low Fo values and Ni contents in olivine from the three intrusions compared to those from Ni-Cu deposits in NW China, as well as those in the Voisey’s Bay deposit in Canada, indicate that the three intrusions were crystallized from relatively evolved magmas. The Cu/Zr ratios of rocks of the Oortsog, Dulaan, and Nomgon intrusions are higher than 1, suggesting that these rocks contain cumulus sulfide. This, coupled with the presence of rounded sulfide inclusions in olivine of the Oortsog and Dulaan intrusions, suggests that sulfide saturation occurred before or during olivine crystallization. The distribution patterns of platinum group elements (PGEs) of the Dulaan and Oortsog intrusions record slight Rh, Pt, and Pd (PPGE) enrichment relative to Os, Ir, and Rh (IPGE). Furthermore, the Ni/Cu ratios of sulfide-bearing rocks from the Oortsog intrusion vary from 1.8 to 3.8, which are consistent with those of the Ni-Cu sulfide deposits in NW China. In contrast, the Ni/Cu ratios of sulfide-bearing rocks from the Nomgon intrusion are extremely low (0.03 to 0.07). This, together with the significant enrichment in PPGE relative to IPGE, suggests that these sulfides of the Nomgon intrusion were segregated from a magma that was extremely enriched in Cu and PPGE but depleted in Ni and IPGE. The characteristics of the chalcophile elements in these intrusions are attributed to the fact that the derivation of the Nomgon magma was significantly different from that of the Dulaan and Oortsog parental magmas. Overall, although the parental magmas of the intrusions in central Mongolia are more evolved than those in NW China, they are comparable in terms of the sizes of their intrusions, constituent minerals, and mineral chemistry. These similarities suggest that the intrusions in central Mongolia have economic Ni-Cu sulfide potential. Furthermore, intrusions similar to the Nomgon intrusion may feature PGE mineralization potential.     

东天山图拉尔根大型铜镍硫化物矿床的斜长石主量成分特征：对矿床成因的指示

图拉尔根镍铜矿床产于康古尔塔格-黄山韧性剪切带NEE向的次级挤压破碎带上,位于黄山-镜儿泉岩浆铜镍成矿带的东段。矿田范围内有I、II、III号3个镁铁质-超镁铁质杂岩体,主要铜镍矿体就位于I号基性-超基性杂岩体内。该杂岩体主要包括辉长岩、角闪橄榄岩、二辉橄榄岩、角闪辉橄岩等岩相,其中角闪橄榄岩为主要的赋矿岩相。本文通过对矿物颗粒镜下形态、结构、构造的观察,对钻孔中赋矿岩相、不含矿岩相的斜长石进行系统的成分分析和对比,来进一步限定岩浆的演化及矿床成因。图拉尔根矿床中主要造岩矿物的结晶次序为:橄榄石-辉石(角闪石)-角闪石。仅见极少数斜长石颗粒包裹橄榄石,而与辉石和角闪石没有明显的包裹关系,可能是略晚于橄榄石结晶的另一单独结晶序列的矿物。赋矿的角闪橄榄岩中斜长石与硫化物含量呈负相关性。斜长石中SiO2和Al2O3含量相对集中,CaO、Na2O、K2O含量变化范围大。SiO2含量从深部到浅部,表现出含量从低到高变化的趋势,说明岩体中斜长石受同源岩浆结晶分异作用的控制。越靠近富硫化物的角闪橄榄岩,斜长石中CaO和Al2O3含量越高,SiO2、Al2O3、CaO、Na2O、K2O等主量元素的含量变化范围较大。因此,斜长石的主量成分可以作为接近硫化物富矿体的指示。