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1.
达拉库岸镁铁-超镁铁质岩体位于东昆仑造山带南带之喀拉米兰晚古生代沟弧系,主要由二辉橄榄岩、单辉橄榄岩、橄榄二辉岩、单辉辉石岩和辉长岩组成。辉长岩的锆石U-Pb谐和年龄为244.4±1.5Ma,属于中三叠世。岩石普遍弱富集稀土元素和大离子亲石元素(Rb、Ba、Sr),亏损不相容元素(Nb、Ta)。岩体原生岩浆为高镁拉斑玄武质岩浆(Mg O 11.4%,Fe O10.8%)。元素地球化学和Nd、Sr同位素组成特征表明岩浆源区为富集岩石圈地幔,岩浆运移和侵位过程中遭受不同程度地壳物质的同化混染作用。依据橄榄石组分模拟获得橄榄石结晶过程中母岩浆达到硫饱和,并发生硫化物的熔离作用。从岩体特征、矿石结构、原生岩浆性质、深部硫化物熔离和物探信息等方面综合分析,岩体具有形成岩浆型铜镍硫化物矿床的良好条件。 相似文献
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3.
野芨里岩体分布于金川铜镍(铂)硫化物矿床北偏东约100 km处,位于内蒙古境内。岩体主要由单斜辉石橄榄岩、二辉橄榄岩、辉长岩和闪长岩组成。岩体的稀土元素配分模式显示轻稀土元素略为富集,曲线为近于平坦型,w(La)N/w(Yb)N=1.866～2.713,不具备会聚型板块边缘玄武岩的特点;εNd(t)＞0,为亏损地幔源区特征。Mg#值和Ni丰度显示其为岩浆早期阶段堆晶作用的产物。与金川矿区超镁铁质岩体比较,二者均为华北大陆边缘成矿系统的组成部分,m/f值显示二者主要为铁质超基性岩,稀土元素及微量元素显示其具相似的地球化学特征,但野芨里岩体具早期堆晶就地熔离的特征,而金川岩体具有深部熔离-多期贯入的特征;野芨里岩体中Ni相对亏损。这些特征表明野芨里岩体具成矿的可能性。 相似文献
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《地学前缘》2017,(2):130-139
阿拉善地块西南缘的北海子岩体由橄榄辉长岩、辉长辉绿岩、闪长岩相组成。岩体中含矿岩相为橄榄辉长岩,存在大量的硫化物珠滴,硫化物主要由磁黄铁矿、镍黄铁矿与黄铜矿组成,指示岩浆深部发生过硫化物不混溶作用。岩石地球化学数据显示北海子岩体属于铁质超基性岩(m/f=2.32~5.01),富集轻稀土元素,具有明显的Nb、Ta负异常;负εNd(t)值与高(87Sr/86Sr)i值证明岩浆源区为富集型岩石圈地幔,同位素与微量元素比值都指示岩浆在上升过程中受到了明显的上地壳物质混染。橄榄辉长岩中单颗粒锆石U-Pb年龄为(374±4)Ma,结合区域地质研究,北海子岩体可能形成于陆内造山后伸展环境,与岩石圈地幔拆沉和对应的软流圈物质上涌有关,由富集型岩石圈地幔部分熔融产生的玄武质岩浆侵位形成。 相似文献
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四顶黑山岩体主要由超镁铁质岩和镁铁质岩组成。超镁铁质岩由橄榄岩、角闪橄榄岩、辉橄岩、辉石岩等组成;镁铁质岩由辉长岩、角闪辉长岩、橄榄辉长岩等组成。本次对辉长岩进行了全岩Sm-Nd同位素分析,得到的等时线年龄为327±9.0Ma,初始εNd（t）=＋3.97,表明镁铁质—超镁铁质岩中辉长岩形成于早石炭世末。属于富集地幔向亏损地幔过渡类型。这一年龄的确定,为探讨北山—天山结合部晚古生代镁铁质—超镁铁质岩的成因机制和该区的区域地质演化提供了有效的年代学依据。 相似文献
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阿拉善地块南缘是镁铁质—超镁铁质岩体的重要分布区,自北向南可分为北大山岩带、龙首山岩带和北海子岩带。本文主要以北大山岩带为研究对象,通过对野芨里岩体、青疙瘩岩体及鄂博沟岩体的岩石学、岩石地球化学、微量元素、稀土元素等研究,探讨了北大山镁铁质—超镁铁质岩体的成因类型和形成构造环境。3个岩体主量元素特征显示Mg#=76~87,橄榄岩类w(Al2O3)=3.2%~5.2%,但辉长岩、辉绿岩类明显高于该值,说明北大山镁铁质—超镁铁质岩熔融程度整体不高,该区岩体属于镁质超基性岩,并且具有富铁趋势;稀土元素特征显示稀土总量(ΣREE)在5.68×10-6~11.5×10-6之间,野芨里岩体LREE稍富集,而青疙瘩及鄂博沟岩体LREE明显富集;微量元素特征显示北大山镁铁质—超镁铁质岩体的成岩构造环境为板内拉张环境,岩浆在侵位过程中受到上地壳的混染作用,微量元素原始地幔标准化蛛网图显示Ni明显亏损,有利于镍成矿。 相似文献
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内蒙古乌拉特中旗地处华北陆块北缘西段,大地构造分区属于狼山-白云鄂博陆缘裂谷。区域上,镁铁质-超镁铁质岩呈东西向带状分布,断续出露长约300km,宽约30km。该镁铁质-超镁铁质岩带内铜镍矿床(点)较为发育,克布为该带内一个中-小型铜镍硫化物矿床。克布镁铁质-超镁铁岩体出露面积约45km2,主要由辉长岩相和橄榄岩相组成,辉长岩相为岩体的主要岩相,橄榄岩相为主要的赋矿岩石,两个相带相伴产出,呈渐变过渡关系。本文采用LA-ICP-MS锆石U-Pb法测年,获得克布斜长方辉橄榄岩年龄为258.1±1.8Ma(MSWD=2.3),属于晚二叠世。岩石主、微量及稀土元素分析结果表明,岩石样品属铁质镁铁质-超镁铁质岩,具有拉斑玄武岩系列演化趋势,并相对富集大离子亲石元素(Rb、Sr、Ba),亏损高场强元素(Nb、Ta、Zr、Hf、Ti),以及具有轻稀土富集[(La/Yb)N=2.47~11.29]的右倾型稀土配分模式。以橄榄石-熔体平衡原理估算克布镁铁质-超镁铁质岩体母岩浆的MgO含量为10.1%,FeO为12.1%,应为高镁的拉斑玄武质岩浆。综合分析认为,克布镁铁质-超镁铁质岩体应形成于后碰撞伸展阶段,岩浆源区由被消减板片交代的地幔楔物质和软流圈物质组成。橄榄石和辉石等富镁铁矿物的分离结晶和富硅地壳物质的混染可能对硫化物熔离富集成矿起到了关键性作用。 相似文献
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《地质与勘探》2015,(2)
尕秀雅平东含铜镍硫化物镁铁-超镁铁质岩体位于柴达木地块北缘,主要由蛇纹石化纯橄岩、单辉橄榄岩、橄榄辉石岩、辉石岩、辉长岩及斜长岩组成,侵位于古元古代达肯大坂岩群。本文对组成岩体的4件橄榄辉石岩样品和3件含矿岩石样品进行铂族元素分析,其∑PGE=8.82×10-9~84.8×10-9,原始地幔标准化配分曲线均呈左倾型式。利用Ni/Cu、Pd/Ir等相关参数确定原生岩浆为高镁玄武质岩浆,而低程度的地幔部分熔融作用是导致PPGE与IPGE强烈分异及Ru亏损的主要原因。岩体在形成过程中有一定程度地壳物质的混染作用,但早期硫化物的熔离作用不明显。同时,PGE元素间的协变关系显示热液蚀变作用对全岩PGE丰度影响不大。 相似文献
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尕秀雅平东含铜镍硫化物镁铁-超镁铁质岩体位于柴达木地块北缘,主要由蛇纹石化纯橄岩、单辉橄榄岩、橄榄辉石岩、辉石岩、辉长岩及斜长岩组成,侵位于古元古代达肯大坂岩群。本文对组成岩体的4件橄榄辉石岩样品和3件含矿岩石样品进行铂族元素分析,其∑PGE=8.82×10-9~84.8×10-9,原始地幔标准化配分曲线均呈左倾型式。利用Ni/Cu、Pd/Ir等相关参数确定原生岩浆为高镁玄武质岩浆,而低程度的地幔部分熔融作用是导致PPGE与IPGE强烈分异及Ru亏损的主要原因。岩体在形成过程中有一定程度地壳物质的混染作用,但早期硫化物的熔离作用不明显。同时,PGE元素间的协变关系显示热液蚀变作用对全岩PGE丰度影响不大。 相似文献
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牛鼻子梁镍铜矿床是柴达木地块周缘新发现的一个岩浆硫化物矿床。该矿床所赋存的牛鼻子梁镁铁质-超镁铁质杂岩体出露面积约8km2,主要由橄榄岩、橄榄二辉岩、橄榄辉长岩、辉长岩组成。含矿岩石主要为橄榄岩和橄榄辉长岩。岩石和矿石的∑PGE含量(0.65×10-9～8.65×10-9)很低,可能是因为源区部分熔融程度较低导致的;在原始地幔标准化配分曲线图中,相对于Ni、Cu元素,PGE显示亏损,这是因为早期发生的硫化物熔离带走了大量PGE。星点状-浸染状矿石的(187Os/188Os)i比值为0.1944～0.5462,γOs值为56～338,显示在岩浆侵位和成矿过程中有较多地壳物质的加入。由于地壳混染而导致浸染状矿石Os同位素组成不均一,从而得出Re-Os等时线年龄(645Ma)大于岩体锆石年龄(367Ma)。 相似文献
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笔架山东基性—超基性岩体位于塔里木板块东北部的新疆北山地区,是笔架山岩带中最东边的一个岩体,岩体形态为椭圆状,出露面积约5 km2.由含长单辉橄榄岩、橄榄辉长岩、含橄辉长岩、辉长岩以及辉绿岩组成.含橄榄石较多的岩石属拉斑玄武岩系列,而辉长岩属钙碱性系列.岩相学、岩石化学和微量元素地球化学特征表明岩浆演化过程中经历了橄榄石、辉石、斜长石的分离结晶作用.Nd、Sr、Pb同位素组成和岩石地球化学特征反映出岩浆与围岩之间存在物质交换.笔架山东岩体的岩浆源区为OIB型地幔源区,原生岩浆为高镁拉斑玄武岩浆[w(MgO)=11.2％],这些性质与塔里木板块东北部其他基性-超基性岩体的特征相似,表明塔里木板块东北部二叠纪基性—超基性岩体的源区主要为OIB型地幔,可能与地幔柱有关. 相似文献
12.
新疆北山地区旋窝岭镁铁-超镁铁岩体的年代学、岩石矿物学和地球化学研究 总被引：5，自引：4，他引：1
新疆北山地区的旋窝岭岩体侵位于下石炭统红柳园组变质砂岩中,辉长岩的锆石SIMSU-Pb定年结果为260.7±2.0Ma,晚于区域上其它岩体的成岩年龄。该岩体由橄榄岩、橄长岩、橄榄辉长岩和辉长岩组成,岩石较新鲜,具有典型的包橄结构和辉长结构,各岩性中均可见斜长石,而斜方辉石仅在辉长岩中出现。橄榄石的Fo值在80～85之间,NiO含量介于0.1%～0.2%之间;单斜辉石主要为普通辉石和透辉石,斜方辉石为古铜辉石。这些镁铁质矿物和斜长石成分与全岩的地球化学特征具有很好的相关性,说明该岩体母岩浆的演化过程主要受控于结晶分异作用。全岩的MgO含量在9.5%～21.8%之间,具有平坦的稀土配分型式和正Eu异常以及微量元素Nb、Zr、Hf的负异常等。因此,旋窝岭岩体可能是在北山裂谷形成过程中由于岩石圈地幔高程度部分熔融形成的高镁玄武质岩浆分异演化的产物,具有一定的铜镍硫化物矿床的成矿潜力。 相似文献
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A. A. Yaroshevskii S. V. Bolikhovskaya E. V. Koptev-Dvornikov 《Geochemistry International》2006,44(10):953-964
The application of the principle and algorithm of the cluster analysis of rock compositions in magmatic complexes, which were
described elsewhere, made it possible to reveal the spaceless and spatial geochemical structure of the Yoko-Dovyren layered
mafic-ultramafic massif. The diversity of rocks composing this intrusion was demonstrated to comprise eleven discrete geochemical
types (clusters): dunites, harzburgites, melanotroctolites, troctolites, two types of olivine gabbro, two types of olivine
gabbronorites, quartz gabbronorites, and granophyres. These geochemical types of rocks and the corresponding fractionation
parameters (the iron atomic fraction f of mafic minerals and the anorthite concentration An of plagioclase) define a succession corresponding to the tendencies in the crystallization of a magma of respective composition.
This geochemical succession is in complete agreement with the succession in which rocks were formed in the intrusion (from
dunite in its bottom part to quartz gabbronorites and granophyres near its roof) and is complicated by cyclical repetitions.
The main tendency revealed in the cyclic layering is as follows: cyclical intercalations consist of rocks corresponding to
the neighboring members of the rock succession (plagiodunites and melanotroctolites, melanotroctolites and troctolites, troctolites
and olivine gabbro, olivine gabbro and olivine gabbronorites). These tendencies are closely similar to those identified in
the Kivakka intrusion, a fact suggesting that these tendencies can be common for all layered complexes of mafic and ultramafic
rocks.
Original Russian Text ? A.A. Yaroshevskii, S.V. Bolikhovskaya, E.V. Koptev-Dvornikov, 2006, published in Geokhimiya, 2006,
No. 10, pp. 1027–1039. 相似文献
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新疆阿尔泰库卫铜镍硫化物-钛铁氧化物复合型矿化镁铁-超镁铁质杂岩体成因 总被引：3，自引：2，他引：1
库卫镁铁-超镁铁质杂岩体位于新疆阿尔泰南缘,兼具铜镍矿化岩体和钒钛铁矿化岩体的双重特征,主要组成岩石类型有中粒辉长岩、条带状橄榄辉长岩、橄榄苏长辉长岩、角闪辉长岩和含橄辉长岩等。本文采用LA-ICP-MS锆石U-Pb定年法,获得中粒辉长岩、橄榄苏长辉长岩和含橄辉长岩的加权平均年龄分别为398.7±3.7Ma、397.5±2.3Ma和385.2±1.6Ma,表明库卫岩体是早中泥盆世构造-岩浆活动的产物。岩体的主量元素显示其属亚碱性系列,并具有向拉斑系列岩石演化的趋势。具有Ba、U、Ta、Pb、Sr、Ti和Eu的正异常,Th的负异常,显示了相似的LREE相对富集的右倾型配分模式,表明它们可能为同源岩浆演化的产物。结合地球化学特征和区域地质背景,推测库卫岩体为早中泥盆世俯冲消减环境的产物,其原始岩浆可能来源于受俯冲物质交代的地幔楔和软流圈的混合体,不同的岩石类型是相似来源的岩浆经强烈分异的结果。库卫岩体兼具铜镍矿化岩体和钒钛铁矿化岩体的双重特征,但形成铁钛矿床的潜力略显不足。 相似文献
15.
新疆东天山黄山东岩体橄榄石成因意义探讨 总被引：12，自引：6，他引：6
黄山东岩体位于新疆东天山造山带中段,由四次岩浆侵入形成:第一次侵入形成了岩体上部的橄榄辉长岩、角闪辉长岩和闪长岩,构成岩体的主体;第二次侵入形成辉长苏长岩,呈岩墙状分布于岩体西端和西北部;第三次侵入岩石为斜长二辉橄榄岩,位于岩体下部,为主要的赋矿岩石;第四次侵入岩石为底部角闪辉长岩。橄榄石为第三次侵入的斜长二辉橄榄岩和第一次侵入的橄榄辉长岩主要造岩矿物之一,橄榄石的镁橄榄石牌号(Fo)值介于68.5～82.5之间。其中含硫化物斜长二辉橄榄岩中的橄榄石具有较高的Fo值(79.7～82.5);斜长二辉橄榄岩中橄榄石的Fo值为78.3～79.9;而基性程度较低的橄榄辉长岩中橄榄石具有较低的Fo值(68.5～72.2)。利用橄榄石矿物成分计算得出黄山东岩体母岩浆Mg#(Mg2+/(Mg2++Fe2+))为0.59,为原生玄武质岩浆经历结晶分异作用形成。模拟计算结果显示黄山东岩体不含矿岩石中橄榄石是母岩浆经过2%的橄榄石结晶分异且硫达到饱和后,在硫化物熔离的同时岩浆发生橄榄石结晶而形成,并且橄榄石︰硫化物≈50︰1,部分橄榄石成分投点在橄榄石结晶和硫化物熔离的模拟曲线右下侧,指示它们可能受到晶间硅酸盐熔浆作用的影响。含硫化物斜长二辉橄榄岩中Fo值与Ni含量呈负相关关系,说明橄榄石与硫化物熔体之间发生了Fe-Ni交换反应。 相似文献
16.
SUN Tao QIAN Zhuangzhi THAKURTA Joyashish YANG Shenghong XU Gang DUAN Jun GAO Bo WANG Jing 《《地质学报》英文版》2018,92(3):952-971
The Sidingheishan mafic-ultramafic intrusion is located in the eastern part of the Northern Tianshan Mountain, along the southern margin of the Central Asian Orogenic Belt in northern Xinjiang autonomous region of China. The Sidingheishan intrusion is mainly composed of wehrlite, olivine websterite, olivine gabbro, gabbro and hornblende gabbro. At least two pulses of magma were involved in the formation of the intrusion. The first pulse of magma produced an olivine-free unit and the second pulse produced an olivine-bearing unit. The magmas intruded the Devonian granites and granodiorites.An age of 351.4±5.8 Ma(Early Carboniferous) for the Sidingheishan intrusion has been determined by U-Pb SHRIMP analysis of zircon grains separated from the olivine gabbro unit. A U-Pb age of 359.2±6.4 Ma from the gabbro unit has been obtained by LA-ICP-MS. Olivine of the Sidingheishan intrusion reaches 82.52 mole% Fo and 1414 ppm Ni. On the basis of olivine-liquid equilibria, it has been calculated that the MgO and FeO included in the parental magma of a wehrlite sample were approximately10.43 wt% and 13.14 wt%, respectively. The Sidingheishan intrusive rocks are characterized by moderate enrichments in Th and Sm, slight enrichments in light REE, and depletions in Nb, Ta, Zr and Hf. The ε_(Nd)(t) values in the rock units vary from +6.70 to +9.64, and initial ~(87)Sr/~(86)Sr ratios range between 0.7035 and0.7042. Initial ~(206)Pb/~(204)Pb, ~(207)Pb/~(204)Pb and ~(208)Pb/~(204)Pb values fall in the ranges of 17.23-17.91,15.45-15.54 and 37.54-38.09 respectively. These characteristics are collectively similar to the Heishan intrusion and the Early Carboniferous subduction related volcanic rocks in the Santanghu Basin, North Tianshan and Beishan area. The low(La/Gd)_(PM) values between 0.26 and 1.77 indicate that the magma of the Sidingheishan intrusion was most likely derived from a depleted spinel-peridotite mantle.(Th/Nb)_(PM)ratios from 0.59 to 20.25 indicate contamination of the parental magma in the upper crust.Crystallization modeling methods suggest that the parental magma of the Sidingheishan intrusion was generated by flush melting of the asthenosphere and subsequently there was about 10 vol%contamination from a granitic melt. This was followed by about 5 vol% assimilation of upper crustal rocks. Thus, the high-Mg basaltic parental magma of Sidingheishan intrusion is interpreted to have formed from partial melting of the asthenosphere during the break-off of a subducted slab. 相似文献
17.
扬子地块北缘新元古代望江山层状岩体矿物成分和铂族元素特征:对岩浆演化过程和构造环境的制约 总被引：1，自引：1，他引：0
望江山层状岩体位于扬子地块北缘新元古代汉南杂岩带中,岩体从底部到顶部由超镁铁质岩过渡为中性岩:底部主要由辉石岩和橄长岩组成;中部为辉长苏长岩和辉长岩;上部为辉长岩和闪长岩。研究以中部岩相带橄榄辉长苏长岩、辉长苏长岩和辉长岩为对象,通过主要矿物的主微量元素和全岩主微量元素的分析,查明望江山岩体来源于尖晶石二辉橄榄岩组成的大陆下岩石圈地幔,并且地幔源区受到了来自俯冲板片流体的交代,岩体中部带的母岩浆为拉斑玄武质岩浆。钛铁矿—磁铁矿矿物对成分计算表明,母岩浆在形成时具有较高氧逸度。通过单斜辉石压力计得到岩体的侵位深度约为12.9~18 km。对岩体母岩浆橄榄石分离结晶过程的模拟计算表明,中部带橄榄石为母岩浆经过~28%分离结晶的产物。此外,铂族元素（PGE）组成暗示岩体并未经历过大规模的硫化物熔离,可能与缺乏地壳物质混染有关。岩体中单斜辉石与岛弧环境堆晶岩中单斜辉石成分相似,不同于裂谷环境中堆晶单斜辉石的成分;同时,全岩Th/Yb和Nb/Yb比值也与岛弧玄武岩比值相似,因此矿物和全岩成分均说明望江山层状岩体应形成于岛弧环境。研究认为扬子北缘在新元古代长期的俯冲过程中,大洋板片断离导致软流圈上涌,提供热源使交代大陆下岩石圈地幔部分熔融形成具有岛弧特征的镁铁质岩浆,在局部伸展环境中上升侵位形成汉南杂岩带中镁铁—超镁铁质层状岩体。 相似文献
18.
The Potato River intrusion is a Keweenawan (1100 Ma) mafic plutonemplaced in Keweenawan volcanics and earlier Proterozoic metasedimentaryrocks along the southeastern flank of the Lake Superior syncline.It comprises the following lithostratigraphic zones: a thinto absent Border zone of altered olivine gabbro; a Lower zoneof olivine gabbro; a Picritic zone of picrite and troctolite;a Middle zone of olivine gabbro and leucogabbro; an Upper zoneof quartz leucogabbro and ferrogabbro; and a Roof zone of granophyricand granitic rocks. Fractional crystallization is evident fromcompositional changes in the rocks and cumulus minerals withstratigraphic height. Elements concentrated in the cumulus mineralsolivine and plagioclase (Mg, Fe2+, Al, Ca, Ni, Co, Cr, Sr) decreasewith height; elements concentrated in the trapped liquid (Na,K, La, Y, Zr, Nb, Rb, Ba) increase with height; and other elements(Ti, Fe3+, P, Ga, V, Sc, Cu, Zn) show complicated behavior relatedto the appearance of additional cumulus phases such as clinopyroxene,Fe-Ti oxides, and apatite. Lower zone rocks contain some sulfide,probably from sulfur derived from the country rock, and theUpper zone has sulfides probably precipitated from an immisciblesulfide liquid. The sulfide-bearing rocks have similaritiesto those of other intrusions, such as Bushveld, Stillwater,and Skaergaard. The picritic and troctolitic rocks of the Picritic zone indicatethat the intrusion was open to additional injections of maficmagma. Roof zone granophyric rocks are residual liquids intrudedalong the upper margin of the intrusion during regional tilting,but Roof zone granitic rocks are probably melted country rock.An attempt is made to estimate by reverse stratigraphic summationthe compositional path of the magma that solidified above thePicritic zone. The first compositions are highly aluminous,which suggests that the upper part of the intrusion has beenenriched in plagioclase by convection-aided crystal sorting.A complementary unit of mafic rocks is not exposed, but it couldbe present down dip. Some of the later compositions are similarto typical Keweenawan high-Al tholeiites. The magma did notundergo extreme iron enrichment, probably because of oxygenfugacity buffering. 相似文献