首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到18条相似文献,搜索用时 112 毫秒
1.
东天山黄山东铜镍矿床铂族元素地球化学特征及其意义   总被引:15,自引:0,他引:15  
黄山东岩体位于东天山北部的土墩—黄山—镜儿泉—图拉尔根镁铁—超镁铁质岩带中段,受康古尔塔格—黄山深大断裂控制,是由二辉橄榄岩、橄榄辉长岩、辉长苏长岩和辉长闪长岩组成的复式岩体。黄山东铜镍硫化物矿床镁铁质岩石和矿石中的铂族元素(PGE)含量很低,其中IPGE(Os, Ir, Ru, Rh)与PPGE(Pt, Pd)含量相近,PPGE略高于IPGE。岩石平均2×10-9,矿石平均86×10-9。在矿石中,PGE含量与硫含量呈正相关关系。在原始地幔标准化图解上,岩石和矿石具有相似的分配模式,PPGE和IPGE之间分异很弱。Ni/Cu—Pd/Ir关系图以及岩石地球化学资料显示,形成黄山东岩体的原始岩浆为MgO含量较高的PGE不亏损的拉斑玄武质岩浆。岩浆在上升的过程中发生过早期硫化物深部熔离,带走了岩浆中大部分的PGE,可能是造成黄山东矿床母岩浆中PGE明显亏损的主要原因。矿石低的Pd/Ir比值(为4.22~17.24,平均值为849)及高的Ir含量(为2.04×10-9~21.45×10-9,平均值为8.79×10-9)显示黄山东矿床成矿过程中后期热液作用不明显。铂族元素地球化学特征和岩石地球化学资料显示了地壳物质的混染以及橄榄石、辉石等矿物的分离结晶是引起该矿床硫饱和并发生硫化物熔离作用而成矿的主要因素。  相似文献   

2.
新疆东部葫芦岩体地表出露面积0.75km2,是由辉长闪长岩、辉长岩、辉石岩、辉橄岩、橄榄岩组成的复式岩体。LA-ICP-MS锆石U-Pb定年,岩体形成年龄为274.5±3.9Ma,是东天山后碰撞伸展环境的产物。岩石和矿石的PGE总量低,其中IPGE与PPGE含量相近,PPGE略高于IPGE。岩石平均7.90×10-9,矿石平均45.57×10-9。在原始地幔标准化图解上,岩石和矿石具有相似的分配模式,PPGE和IPGE之间分异较弱。Ni/Cu-Pd/Ir关系图显示母岩浆主要为高镁的玄武质岩浆。根据矿石Cu/Pd比值114.67×103~157.42×103(平均136.05×103)和岩石Cu/Pd比值11.07×103~294.35×103(平均125.48×103)推断,葫芦矿床成矿母岩浆演化过程中经历了深部硫化物部分熔离的过程,这可能是导致该矿床PGE明显亏损的原因之一。地壳物质的混染(SiO2、S等的加入)以及橄榄石、辉石等矿物的分离结晶,是引起该矿床硫饱和并发生硫化物熔离作用而成矿的主要因素。  相似文献   

3.
白鑫滩铜镍硫化物矿床位于东天山镁铁-超镁铁质岩带西段,受大草滩深大断裂控制,岩体由辉长岩、橄榄辉石岩、辉石橄榄岩组成。白鑫滩岩体的铂族元素(PGE)含量相对较低,其中IPGE(Os、Ir、Ru)与PPGE(Ru、Pt、Pd)含量相近,PPGE略高于IPGE。岩石∑PGE含量3.82×10~(-9)~5.36×10~(-9),平均4.53×10~(-9)。岩石具相似的原始地幔标准化分布型式,PPGE和IPGE之间分异很弱。通过铂族元素源区示踪分析认为,形成白鑫滩岩体的母岩浆为Mg O含量较高的PGE不亏损的拉斑玄武质岩浆,上升过程中遭地壳物质混染及橄榄石等矿物的分离结晶作用,引起该矿床硫饱和并发生硫化物熔离作用而成矿,深部岩浆通道仍具较好的找矿空间。  相似文献   

4.
圪塔山口铜镍矿床位于东天山黄山-镜儿泉-图拉尔根铜镍矿带东段,目前,规模已达小型,以星点状和稀疏浸染状矿石为主。矿石中Ni含量为0.16%~1.39%,Cu含量为0.02%~1.21%,Ni/Cu值为1.15~7.01。铂族元素总量含量较低,为13.11×10-9~828.09×10-9,矿石Pd/Ir值为13.9~20.8,表明成矿后热液活动对铂族元素影响较小。铂族元素原始地幔标准化配分曲线呈明显的左倾型,PPGE含量略高于IPGE。在Ni/Cu-Pd/Ir图解上,圪塔山口矿床母岩浆成分落入高镁玄武岩区域,与国内其他典型铜镍矿床成矿母岩浆性质一致。深部岩浆房内少量硫化物的熔离是导致矿石中PGE亏损的主要原因。铂族元素之间呈较好的正相关性,表明硫化物熔离后未发生明显的分离结晶作用。  相似文献   

5.
为了探讨土墩铜镍硫化物矿床的成矿岩浆来源、岩浆演化过程以及硫化物熔离成矿作用,文章对土墩矿区内不同类型的岩石进行了岩石地球化学特征的研究,认为该矿床的成矿岩浆属于拉斑玄武岩浆系列。岩浆在岩浆房和/或侵位过程中存在着分离结晶作用,并且,在其上升演化过程中可能经历了同化混染作用。首次对该矿区内岩石和矿石的铂族元素地球化学特征开展了研究,发现其岩石及矿石具有一致的物质来源;岩石及矿石的PGE总量都较低,配分模式都为左倾富集PPGE的Pt-Pd型。根据Ni/Cu-Pd/Ir图解和地球化学特征,认为土墩岩体的原始岩浆应是低程度地幔部分熔融岩浆,是MgO含量较高的PGE不亏损的玄武质岩浆。根据Cu/Pd值较高,可以推断土墩矿床的成矿母岩浆在演化过程中经历了深部硫化物部分熔离的过程,这可能是导致该矿床PGE明显亏损的原因之一。同时,根据Cr与PGE和Ni的相关关系,认为其母岩浆可能经历了铬铁矿的分离结晶作用,这也许是导致该矿床硫化物发生熔离作用的重要因素。结合Ti/Y-Zr/Y相关图解及东天山区域地质演化史,笔者认为,土墩矿区的成矿镁铁质-超镁铁质岩体是形成于碰撞后的拉张环境。  相似文献   

6.
对北山地区坡一和罗东含铜镍的镁铁-超镁铁质岩体铂族元素研究表明,两个岩体的铂族元素(PGE)总量较低,PPGE较IPGE富集,原始地幔标准化模式呈正斜率,均较原始地幔亏损,具Ir和Rh的弱负异常。较低的Pd/Ir比值表明岩石主要受岩浆作用控制,后期热液作用影响不明显。两个岩体的原生岩浆均为MgO 含量较高的PGE不亏损的拉斑玄武质岩浆,较高的Cu/Pd、Ti/Pd比值表明岩浆在演化过程中发生了硫化物的熔离。罗东岩体早期矿物相(橄榄石、铬铁矿)的分离结晶作用对岩浆中的硫达到饱和具有重要的贡献,而坡一岩体该作用对硫化物熔离的贡献不明显。坡一和罗东岩体的R值表明两岩体均具有达到中型Ni矿床的潜力。  相似文献   

7.
东昆仑夏日哈木镍矿床地质特征与成因   总被引:10,自引:3,他引:7  
夏日哈木超大型镍矿床位于东昆仑造山带昆中岛弧带内。Ⅰ号含矿岩体主要由橄榄岩相、辉石岩相、辉长苏长岩相等多种岩石类型组成。其中,含矿岩石主要为橄榄岩相、辉石岩相和苏长岩相。矿石构造以准块状_块状、海绵陨铁状和浸染状为主,斑杂状次之,细脉状较少。岩石和矿石的铂族元素(PGE)丰度较低,岩石平均6.45×10-9,矿石平均456.91×10-9。岩石和矿石具有相似的PGE配分模式。矿石样品具有高的Ir丰度(0.284×10-9~1.198×10-9),低的Pd/Ir比值(9.12~22.34,平均值16.41),显示了岩浆型成矿作用特点。铂族元素(PGE)地球化学特征及岩石Ni/Cu_Pd/Ir关系表明,原生岩浆为高镁玄武质岩浆。母岩浆明显亏损PGE,而硫化物的深部熔离可能是导致母岩浆PGE亏损的主要原因。硫同位素特征显示有明显地壳硫的加入。根据铂族元素特征及矿相学、硫同位素特征分析,成矿母岩浆在深部岩浆房分异,为含少量硫化物的岩浆、含较多硫化物的岩浆和矿浆,分阶段脉动式上侵,在上侵过程中和进入终端岩浆房后硫化物继续熔离,是形成夏日哈木镍矿床的主导机制。  相似文献   

8.
青矿山Ni-Cu-PGE矿床位于四川会理县小关河地区,是峨眉山大火成岩省中典型含铂岩浆硫化物矿床之一。本文对该矿床开展了Re-Os同位素组成的分析研究。分析结果表明,不同类型岩矿石的初始Os同位素组成具有明显的不均一性,主要区分出三种不同Os同位素组成的岩矿石类型:不含硫化物的橄辉岩具低γOs,变化范围从15.3到40.3;致密块状和浸染状硫化物矿石相近,γOs值在260左右;海绵陨铁状矿石具有最高的放射性Os同位素组成,γOs值在1000左右。分析认为,青矿山Ni-Cu-PGE矿床是多级岩浆房演化的结果,原始岩浆具有苦橄质岩浆的性质,成矿岩体中不含硫化物的橄辉岩具有低的放射性Os同位素组成,其母岩浆不是矿石硫化物的直接母体;致密块状和浸染状硫化物矿石与海绵陨铁状矿石也具有不同的放射性Os同位素组成,是成矿岩浆演化过程中不同期次岩浆硫化物熔离形成的。模式分析认为:(1)原始岩浆在深部岩浆房受到下地壳混染(约1.8%),造成少量Cu、Ni及PGE元素进入熔离硫化物形成PGE适度亏损的成矿母岩浆;(2)海绵陨铁状矿石硫化物是PGE适度亏损的成矿母岩浆受下地壳二次混染形成的具有很高放射性Os同位素组成的岩浆(γOs(t=260Ma)高达1000)经二次硫化物熔离(R≈1000)所形成;(3)PGE适度亏损的成矿母岩浆受上地壳二次混染(约6.7%),形成具有较高放射性Os同位素组成的岩浆(γOs(t=260Ma)在260左右)并发生二次硫化物熔离(R≈5000),部分熔离硫化物积聚成矿浆形成块状硫化物矿石,未得到充分积聚的熔离硫化物形成浸染状硫化物矿石。Os同位素组成的不均一性表明青矿山Ni-Cu-PGE矿床为岩浆通道系统成矿,是多级岩浆房演化过程中不同期次含矿岩浆在岩浆通道系统中复合的结果。  相似文献   

9.
中亚造山带南缘东天山地区是我国战略资源Ni的重要产区,图拉尔根矿床是该地区众多铜镍矿床中以岩体高矿化比例为特色的矿床。图拉尔根杂岩体由晚石炭世基性岩体(辉长岩、角闪辉长岩)和早二叠世超基性岩体(二辉橄榄岩、角闪橄榄岩)组成,矿体呈透镜状、“悬浮”状产出于超镁铁岩体的中部和中上部,矿化类型为块状/半块状、海绵陨铁状、稠密/稀疏浸染状、星点状、斑杂状以及少量珠滴状矿化。不同类型矿石∑PGE变化较大(10.8×10-9~208×10-9),除块状矿石样品外,其他类型矿石(S<15%)S与PGE、IPGE与PGE元素之间均显示良好正相关,表明PGE含量变化主要受控于R因子(100~5000)变化;块状矿石的上述元素间呈现离散现象,亦反映单硫化物固溶体分异的影响。母岩浆中Pt和Pd的显著亏损以及矿石中Cu和Pd的强烈解耦,表明图拉尔根母岩浆经历了深部硫化物的熔离。Pd/Ir比值揭示的高镁玄武质岩浆性质和含水地幔源区可能的低程度部分熔融,表明源区硫化物残留也可能造成PGE的亏损。图拉尔根矿床的187Os/188  相似文献   

10.
朱飞霖  白梅  陶琰 《岩石学报》2017,33(7):2225-2240
核桃树富铂岩浆硫化物矿床位于四川会理县小关河地区,是峨眉山大火成岩省中含较高铂族元素含量的岩浆硫化物矿床之一。本文通过对核桃树岩体及部分硫化物矿石主量元素、微量元素及铂族元素的系统分析,讨论了该岩体的岩浆源区及母岩浆性质、地幔部分熔融程度,并探讨了其成因机制。研究认为,核桃树含矿岩体属拉斑玄武岩成因系列,具有与峨眉山玄武岩相似的微量元素组成特征,是峨眉山大火成岩省构造-岩浆活动的产物;铂族元素的原始地幔标准化配分型式与金宝山铂钯矿相似,没有PGE相对于Ni和Cu的明显亏损,Pt和Pd相对Os、Ir、Ru和Rh富集,为PPGE富集的左倾型式,Pd/Ir=1.5~13.1,低于一般大陆拉斑玄武岩,与原始地幔接近。通过岩石地球化学及模拟分析表明,成矿母岩浆MgO约为11.93%、SiO_2约为49.88%、FeOT约为13.71%、TiO_2约为2.61%,为高Mg拉斑玄武质岩浆,是由类似于洋岛玄武岩岩浆源区成分的地幔经过较高程度(约20.17%)的部分熔融形成的苦橄质岩浆演化而来。与小关河地区主要的几类岩浆硫化物矿床的镍铜铂族元素组成及硫化物熔离模式对比分析发现,核桃树高的PGE含量和低的Cu/Pd比值说明了该矿床的硫化物是从PGE不亏损的玄武质岩浆中熔离出来的,类似金宝山矿床。成岩成矿机制分析认为,部分熔融形成的苦橄质岩浆在上升的过程中,发生了以橄榄石(约12.7%)为代表的镁铁质矿物堆积,并形成残余髙镁玄武质岩浆;部分残余髙镁玄武质岩浆向浅部运移过程中,由于温度降低、混染等因素的影响,导致岩浆S饱和,触发硫化物熔离作用的发生(R值为2000~50000),熔离出硫化物熔体与岩浆通道内晶出的橄榄石构成含矿"晶粥",在构造挤压作用下,在浅部岩浆房中由于重力影响发生堆积作用形成具有较富PGE的含矿岩体,R值较大变化正好与PGE含量较大变化相对应。  相似文献   

11.
对新疆北山地区红石山镁铁-超镁铁质岩体中含铜镍的硫化物矿石和岩石进行了铂族元素和Re-Os同位素地球化学特征研究,结果表明,矿石及岩石的铂族元素(PGE)总量较低,变化于0.54×10-9~15.84×10-9之间。较低的Pd/Ir比值表明岩石主要受岩浆作用控制,后期热液作用影响不明显。较高的Cu/Pd和Ti/Pd比值表明岩浆在演化过程中发生了硫化物的熔离。岩体的母岩浆为有早期结晶橄榄石加入的高镁的玄武质岩浆。γOs(t)的变化较大,变化于-282~+282之间,表明有较多的地壳物质混入。地壳物质混染和橄榄石等矿物的分离结晶可能是引起岩浆中的S达到饱和进而熔离的重要因素。红石山岩体是经历了结晶分异和硫化物熔离后橄榄石的堆积体与残余岩浆演化的混合体。  相似文献   

12.
The Kalatongke (also spelt as Karatungk) Ni–Cu–(platinum-group element, PGE) sulfide deposit, containing 33 Mt sulfide ore with a grade of 0.8 wt.% Ni and 1.3 wt.% Cu, is located in the Eastern Junggar terrane, Northern Xinjiang, NW China. The largest sulfide ore body, which occupies more than 50 vol.% of the intrusion Y1, is dominantly comprised of disseminated sulfide with a massive sulfide inner zone. Economic disseminated sulfides also occur at the base of the intrusions Y2 and Y3. The main host rock types are norite in the lower part and diorite in the upper part of each intrusion. Enrichment in large ion lithophile elements and depletion in heavy rare earth elements relative to mid-ocean ridge basalt indicate that the mafic intrusions were produced from magmas derived from a metasomatized garnet lherzolite mantle. The average grades of the disseminated ores are 0.6 wt.% Ni and 1.1 wt.% Cu, whereas those of the massive ores are 2 wt.% Ni and 8 wt.% Cu. The PGE contents of the disseminated ores (14–69 ppb Pt and 78–162 ppb Pd) are lower than those of the massive ores (120–505 ppb Pt and 30–827 ppb Pd). However, on the basis of 100% sulfide, PGE contents of the massive sulfides are lower than those of the disseminated sulfides. Very high Cu/Pd ratios (>4.5 × 104) indicate that the Kalatongke sulfides segregated from PGE-depleted magma produced by prior sulfide saturation and separation. A negative correlation between the Cu/Pd ratio and the Pd content in 100% sulfide indicates that the PGE content of the sulfide is controlled by both the PGE concentrations in the parental silicate magma and the ratio of the amount of silicate to sulfide magma. The negative correlations between Ir and Pd indicate that the massive sulfides experienced fractionation.  相似文献   

13.
The Jinchuan deposit, NW China, is one of the world’s most important Ni-Cu-(PGE) sulfide deposits related to a magma conduit system and is hosted in an ultramafic intrusion. The intrusion is composed of lherzolite and dunite with the two largest sulfide ore bodies (named as ore body 1 and 2) in its middle portion. The sulfide ores may be disseminated, net-textured, or massive. The disseminated and net-textured sulfide ores are characterized by variable but generally low PGE concentrations: 10-3200 ppb Pt, 240-9800 ppb Pd, 17-800 ppb Ir, 25-1500 ppb Ru, and 15-400 ppb Rh in 100% sulfides. The massive sulfide ores are extremely low in Pt (<30 ppb) on a 100% sulfides and have very high Cu/Pd ratios, ranging from 104 to 4.5 × 105. The low PGE contents suggest that the sulfide ores formed from the silicate magmas that had already experienced prior-sulfide separation.Our calculations indicate that if the first stage basaltic magmas had contained 6.3 ppb Pt, 6.2 ppb Pd, and 0.1 ppb Ir, 0.008% sulfide removal would result in PGE-depletion in the residual magma with 0.57 ppb Pt, 0.25 ppb Pd, and 0.009 ppb Ir. The Jinchuan sulfides were formed by a second stage of sulfide segregation from a PGE-depleted magma under silicate/sulfide liquid ratios (R-factor) ranging from 103 to 104 in a deep-seated staging chamber. The massive sulfide ores and some of the net-textured sulfide ores exhibit strong negative Pt-anomalies that cannot be explained by sulfide segregation under variable R-factors. Instead, the sulfide melts that formed the massive ores were segregated from magmas experienced prior fractionation of Pt-Fe alloy. Alternatively, the Pt may have been selectively leached by hydrothermal fluids during remobilization of the sulfide melts that produced the massive sulfides, which occur in cross-cutting veins. We propose that the Jinchuan intrusion and ore bodies were formed by injections of sulfide-free and sulfide-bearing olivine mushes from a deep-seated staging chamber.  相似文献   

14.
金川超大型铜镍硫化物矿床的铂族元素地球化学特征   总被引:19,自引:2,他引:19  
对金川超大型铜镍岩浆硫化物矿床岩石、矿石的铂族元素地球化学特征研究表明 ,金川岩体的平均Cu/Pd值远大于原生地幔岩浆的Cu/Pd值 ,说明其岩石为因硫化物析离而失去Pd的岩浆所结晶 ;且岩石的PGE具有部分熔融趋势 ,与地幔橄榄岩接近 ,这些均指示存在岩浆熔离作用。该矿床岩石、矿石的PGE球粒陨石标准化分布模式比较对应 ,均可分为两种类型 ,反映了岩浆多次侵入、熔离分异同时成岩成矿的特征。另外 ,PGE S关系分析表明其成岩成矿过程中有少量地壳物质混染。PGE地球化学特征参数还指示了其高镁拉斑玄武质母岩浆的性质。  相似文献   

15.
The Binchuan area of Yunnan is located in the western part of the Emeishan large igneous province in the western margin of the Yangtze Block.In the present study,the Wuguiqing profile in thickness of about 1440 m is mainly composed of high-Ti basalts,with minor picrites in the lower part and andesites,trachytes,and rhyolites in the upper part.The picrites have relatively higher platinum-group element(PGE) contents(ΣPGE=16.3-28.2 ppb),with high Cu/Zr and Pd/Zr ratios,and low S contents(5.03-16.9 ppm),indicating the parental magma is S-unsaturated and generated by high degree of partial melting of the Emeishan large igneous province(ELIP) mantle source.The slightly high Cu/Pd ratios(11 000-24 000) relative to that of the primitive mantle suggest that 0.007%sulfides have been retained in the mantle source.The PGE contents of the high-Ti basalts exhibit a wider range(ΣPGE=0.517-30.8 ppb).The samples in the middle and upper parts are depleted in PGE and haveεNd(260 Ma) ratios ranging from -2.8 to -2.2,suggesting that crustal contamination of the parental magma during ascent triggered sulfur saturation and segregation of about 0.446%-0.554% sulfides,and the sulfide segregation process may also provide the ore-forming material for the magmatic Cu-Ni-PGE sulfide deposits close to the studied basalts.The samples in this area show Pt-Pd type primitive mantle-normalized PGE patterns,and the Pd/Ir ratios are higher than that of the primitive mantle(Pd/Ir=1),indicating that the obvious differentiation between Ir-group platinum-group elements(IPGE) and Pd-group platinum-group elements(PPGE) are mainly controlled by olivine or chromites fractionation during magma evolution.The Pd/Pt ratios of most samples are higher than the average ratio of mantle(Pd/Pt=0.55),showing that the differentiation happened between Pt and Pd.The differentiation in picrites may be relevant to Pt hosted in discrete refractory Pt-alloy phase in the mantle;whereas the differentiation in the high-Ti basalts is probably associated with the fractionation of Fe-Pt alloys,coprecipitating with Ir-Ru-Os alloys.Some high-Ti basalt samples exhibit negative Ru anomalies,possibly due to removal of laurite collected by the early crystallized chromites.  相似文献   

16.
The platinum-group element geochemistry of rocks and ores from Jinchuan super-large copper-nickel sulfide deposit is systemically studied in this paper. The Cu/Pd mean ratio of Jinchuan intrusion is lower than that of original mantle magma, which indicates that these ultrabasic rocks were crystallized from magma that lost Pd in the form of melting segregation of sulfides. The PGE of the rocks show trend of partial melting, similar to that of mantle peridotite, which shows that magma formation occurs during rock-forming and ore-forming processes. The chondrite normalized PGE patterns of the rocks and ores are well related to each other, which signifies the signatures of multi-episode magmatic intrusion, melting and differentiation in the formation processes of rocks and ores. In addition, analyses about the relation between PGE and S, and study on Re-Os isotopes indicate that few contamination of the crustal substances occurred during the magmatic intrusion and the formation of deposit. However, contamination by crustal substances helps to supply part of the S for the enrichment of PGE. Meanwhile, the hydrothermal process is also advantageous for the enrichment of PGE, especially lbr Pt and Pd, due to deep melting segregation. The characteristic parameters (such as Pt/(Pt+Pd), (Pt+Pd)/(Ru+Ir+Os), Pd/Ir, Cu/(Ni+Cu), and so on.) for platinum-group elements for Jinchuan sulfide copper-nickel deposit show the same features as those for sulfide copper-nickel deposit related to basic magma, which also illustrates its original magma property representative of Mg-high tholeiite. Therefore, it is the marie (not ultramafic) magma that resulted in the formation of the superlarge sulfide copper-nickel deposit enriched in Cu and PGE. To sum up, the geochemical characteristics of platinum-group elements in rocks and ores from Jinchuan copper-nickel sulfide deposit are constrained by the continental rift tectonic environment, the parent magma features, the enriched mantel magma source, the complex metallogenesis and PGE geochemical signatures, and this would be rather significant for the study about the genetic mechanism of copper-nickel sulfide deposits.  相似文献   

17.
The Qingkuangshan Ni-Cu-PGE deposit, located in the Xiaoguanhe region of Huili County, Sichuan Province, is one of several Ni-Cu-PGE deposits in the Emeishan Large Igneous Province (ELIP). The ore-bearing intrusion is a mafic-ultramafic body. This paper reports major elements, trace elements and platinum-group elements in different types of rocks and sulfide-mineralized samples in the intrusion. These data are used to evaluate the source mantle characteristics, the degree of mantle partial melting, the composition of parental magma and the ore-forming processes. The results show that Qingkuangshan intrusion is part of the ELIP. The rocks have trace element ratios similar to the coeval Emeishan basalts. The primitive mantle-normalized patterns of Ni-Cu-PGE have positive slopes, and the ratios of Pd/Ir are lower than 22. The PGE compositions of sulfide ores and associated rocks are characterized by Ru depletion. The PGE contents in bulk sulfides are slightly depleted relative to Ni and Cu, which is similar to the Yangliuping Ni-Cu-PGE deposit. The composition of the parental magma for the intrusion is estimated to contain about 14.65 wt% MgO, 48.66 wt% SiO2 and 15.48 wt% FeOt, and the degree of mantle partial melting is estimated to be about 20%. In comparison with other typical Ni-Cu-PGE deposits in the ELIP, the Qingkuangshan Ni-Cu-PGE deposit has lower PGE contents than the Jinbaoshan PGE deposit, but has higher PGE contents than the Limahe and Baimazhai Ni-Cu deposit, and has similar PGE contents to the Yangliuping Ni-Cu-PGE deposit. The moderate PGE depletions in the bulk sulfide of the Qingkuanghan deposit suggest that the parental magma of the host intrusion may have undergone minor sulfide segregation at depth. The mixing calculations suggests that an average of 10% crustal contamination in the magma, which may have been the main cause of sulfide saturation in the magma. We propose that sulfide segregation from a moderately PGE depleted magma took place prior to magma emplacement at Qingkuangshan, that small amounts of immiscible sulfide droplets and olivine and chromite crystals were suspended in the ascending magma, and that the suspended materials settled down when the magma passed trough the Qingkuangshan conduit. The Qingkuangshan sulfide-bearing intrusion is interpreted to a feeder of Emeishan flood basalts in the region.  相似文献   

18.
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.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号