Geological Relationships Between the Intrusions,Country Rocks,and Ni-Cu-PGE Sulfides of the Kharaelakh Intrusion,Noril′sk Region:Implications for the Roles of Sulfide Differentiation and Metasomatism in Their Genesis     

Peter C. Lightfoot  ;Igor A. Zotov 《西北地质》2014,(1):1-35

The Ni-Cu-platinum group element sulfide ore deposits of the Kharaelakh Intrusion,Noril′sk Region,Siberia,represent a large concentration of sulfides associated with a small differentiated intrusion formed at the edge of the Siberian Craton in the roots of the Siberian Trap flood basalt.The deposit is associated with an intrusion that occupies a flanking periclinal structure adjacent to the Noril′sk-Kharaelakh Fault.The intrusion is strongly differentiated and comprises taxitic gabbrodolerites,picritic gabbrodolerites,and gabbrodolerites within the main body which in turn forms a chonolith within a sheet-like intrusion that extends laterally to form extensive undifferentiated sills of gabbrodolerite.The intrusion substantially replaces the stratigraphy of the country rocks,and although it appears to have exploited the axis of structures developed in response to transtension,the intrusion has created space by both mechanical dilation of stratigraphy and magmatic replacement of pre-existing sedimentary rocks.The frontal lobes of the main intrusion have complex apophyses of gabrodolerite on a range of scales that demonstrate replacement of the sedimentary rocks and link to the development of an extensive metamorphic halo in the country rocks.This halo is much narrower over the main body of the intrusion,and these observations have implications for the thermal history of the intrusion.Mg-skarns and breccias are developed in the roof of the main body of the intrusion.Within the intrusion,the taxitic rocks contain vesicles and the blebby sulfides developed in the picritic and taxitic gabbrodolerites appear to have a linkage to volatile phases.Cuprous sulfide mineralization developed at the roof of the Kharaelakh Intrusion is associated with metamorphosed and skarn-bearing country rocks,and appears to have been generated by a combination of sulfide fractionation and associated metasomatism.The geological relationships appear consistent with a chonolith model for the development of the differentiated intrusion and mineralization,but the extent of metasmorphism of the country rocks appears to be related to the unusual thickness of gabbrodolerite apophyses at the flanks of the intrusion rather than metamorphism produced by the passage of mafic magma through the intrusion.Variations in disseminated sulfide compositions and metasomatic textures in the skarns are described,and a model is proposed which balances traditional views on the evolution of the magma conduits with the impact of magmatic fluids transported through the magma column(i.e.transmagmatic fluids).The importance of structures in controlling the nature of the conduit,and the resultant small intrusions with excess sulfide is a feature of many other Ni-Cu sulfide deposits including Voisey′s Bay,and it is suggested that the sulfides are more likely to have beentransported from depth into their final resting place rather than developed by in-situ equilibration of sulfide with fresh magma in the chonolith.  相似文献   

How many sutures in the southern Central Asian Orogenic Belt：Insights from East Xinjiang-West Gansu（NW China）？   总被引：1，自引：0，他引：1  

Wenjiao Xiao  ;Chunming Han  ;Wei Liul  ;Bo Wan  ;Ji'en Zhang  ;Song  jian Ao  ;Zhiyong Zhang  ;Dongfang Song  ;Zhonghua Tian  ;Jun Luo 《地学前缘(英文版)》2014,5(4):525-536

How ophiolitic mèlanges can be defined as sutures is controversial with regard to accretionary orogenesis and continental growth.The Chinese Altay,East junggar,Tianshan,and Beishan belts of the southern Central Asian Orogenic Belt（CAOB） in Northwest China,offer a special natural laboratory to resolve this puzzle.In the Chinese Altay,the Erqis unit consists of ophiolitic melanges and coherent assemblages,forming a Paleozoic accretionary complex.At least two ophiolitic melanges（Armantai,and Kelameili） in East Junggar,characterized by imbricated ophiolitic melanges,Nb-enriched basalts,adakitic rocks and volcanic rocks,belong to a Devonian-Carboniferous intra-oceanic island arc with some Paleozoic ophiolites,superimposed by Permian arc volcanism.In the Tianshan,ophiolitic melanges like Kanggurtag,North Tianshan,and South Tianshan occur as part of some Paleozoic accretionary complexes related to amalgamation of arc terranes.In the Beishan there are also several ophiolitic melanges,including the Hongshishan,Xingxingxia-Shibangjing,Hongliuhe-Xichangjing,and Liuyuan ophiolitic units.Most ophiolitic melanges in the study area are characterized by ultramafic,mafic and other components,which are juxtaposed,or even emplaced as lenses and knockers in a matrix of some coherent units.The tectonic settings of various components are different,and some adjacent units in the same melange show contrasting different tectonic settings.The formation ages of these various components are in a wide spectrum,varying from Neoproterozoic to Permian.Therefore we cannot assume that these ophiolitic melanges always form in linear sutures as a result of the closure of specific oceans.Often the ophiolitic components formed either as the substrate of intra-oceanic arcs,or were accreted as lenses or knockers in subduction-accretion complexes.Using published age and paleogeographic constraints,we propose the presence of （1） a major early Paleozoic tectonic boundary that separates the Chinese Altay-East Junggar multiple subduction system  相似文献   

东南极拉斯曼丘陵镁铁质麻粒岩的变质作用演化   总被引：5，自引：4，他引：1  

周信  仝来喜  刘小汉  王彦斌  陈义兵 《岩石学报》2014,30(6):1731-1747

拉斯曼丘陵（Larsemann Hills）位于东南极普里兹构造带的中部,研究该区麻粒岩的变质作用演化对于理解普里兹带的构造属性至关重要。通过对该区含石榴石镁铁质麻粒岩转石详细的岩相学观察表明,峰期前进变质阶段矿物组合（M1）由角闪石+斜方辉石+单斜辉石+斜长石+黑云母+钛铁矿±石英±磁铁矿组成,其峰期矿物组合（M2）为石榴石+斜方辉石+单斜辉石+角闪石+钛铁矿±磁铁矿±石英,而代表后期与降压有关的叠加变质组合（M3）为斜方辉石+斜长石+单斜辉石+黑云母+钛铁矿±磁铁矿。矿物化学分析,结果显示其中石榴子石和斜方辉石具有弱的成分环带特征。利用THERMOCALC软件在NCFMASHTO体系下对该麻粒岩进行了详细的热力学模拟,结合传统温压计和平均温压计算结果,得出不同阶段温压条件分别为650~750℃/5.5~6.5kb （M1）,850~950℃/8~8.5kb （M2）,800~900℃/5.5~7.5kb （M3）。其变质作用演化为典型的峰期后近等温减压的（ITD）顺时针P-T轨迹。通过区域上镁铁质麻粒岩的对比分析,我们认为该镁铁质麻粒岩可能来源拉斯曼丘陵基岩露头。结合已有的年代学资料,表明该镁铁质麻粒岩的峰期变质事件可能对应于晚元古代格林威尔期构造事件,而后期退变质作用与早古生代的泛非期构造事件有关,意味着泛非期普里兹带可能是陆内造山带。  相似文献   

红柳沟北镁铁-超镁铁质岩体矿物学特征及矿石成因分析     

周伟  姜常义  杜玮  宋艳芳  凌锦兰  夏明哲  王梦玺  赵彦锋 《岩石矿物学杂志》2014,33(4):671-680

红柳沟北镁铁-超镁铁质岩体位于柴达木陆块北部的欧龙布鲁克微陆块东北缘,呈岩墙状,出露面积约0.1km~2,由方辉橄榄岩、橄榄二辉岩、含长单辉橄榄岩、橄榄辉长苏长岩、暗色橄榄辉长岩、苏长岩、辉长岩等组成,各岩相带在空间上呈渐变过渡关系。电子探针分析结果显示,岩体的主要造岩矿物为贵橄榄石、古铜辉石、普通辉石和斜长石,并且各矿物的结晶温度为1 307~1 122℃。岩体钛铁矿化明显,主要金属矿物为钛铁矿、钛磁铁矿和磁铁矿。利用橄榄石Fo最高值反演出原生岩浆MgO含量为8.49%,FeO含量为10.03%,TiO_2含量为1.63%,为普通玄武质岩浆。通过综合研究各矿物形成的温度和氧逸度条件,认为岩浆从橄榄石结晶到普通辉石结晶,其氧逸度是缓慢升高的,并且氧逸度是控制红柳沟北岩体Ti-Fe氧化物结晶的主要因素。  相似文献   

“蛟龙号”将载科学家开展深海科学研究     

本刊 《海洋地质与第四纪地质》2013,(3):108

2013年"蛟龙号"深潜器将载科学家下濳深海开展科学研究。这些科学家都是在与科学任务相关的前提下由个人申请的,其中还包括一名来自香港的科研人员。他们已完成了较短时间的培训,了解和掌握了潜水器的基本性能,以及潜水器内部的作业规程。本次试验性应用航次分为3个航段。  相似文献   

鄂尔多斯盆地上三叠统延长组长7段富有机质页岩中藻类化石的发现及地质意义          下载免费PDF全文

袁伟  柳广弟  袁红旗 《地质论评》2023,69(1):365-374

鄂尔多斯盆地上三叠统延长组长7段富有机质页岩是该盆地中生界含油系统的主力烃源岩,其有机质丰度高,类型好,具有巨大的生烃潜力。该套烃源岩中有机质的富集很大程度上取决于长7期的高古生产力及其提供的充足的有机质。长7期藻类勃发的存在已被多数学者所接受,但是目前还缺乏直观、有力的证据。笔者等通过薄片和扫描电镜观察、能谱分析,在长7段的脉状黄铁矿附近和碳酸盐结核中发现了属种单一、分布丰度高的藻类化石,它们呈现出近似球状的轮廓,在中部分布着一条裂缝。这些藻类化石的发现具有重要的地质意义,它为长7期的藻类勃发提供了很好的证据,也为该时期热液活动的重要作用提供了有力的支撑。  相似文献   

柴北缘尕秀雅平东和红柳沟北镁铁-超镁铁质岩体锆石U-Pb年龄及其找矿意义   总被引：1，自引：0，他引：1  

周伟  夏明哲  伍学恒  杜玮  汪帮耀  夏昭德  宋艳芳  宋忠宝 《地质通报》2015,34(10):1860-1868

位于柴达木地块北缘构造带内欧龙布鲁克微陆块东缘的2个镁铁-超镁铁质岩体——含Cu-Ni的尕秀雅平东岩体和含Ti-Fe的红柳沟北岩体,前者的LA-ICP-MS锆石U-Pb年龄为408.0±1.5Ma,属早泥盆世;后者的SHRIMP锆石U-Pb年龄为418.3±2.8Ma,属晚志留世。区域地质资料研究表明,东昆仑地区、柴北缘在晚志留世—晚泥盆世处于后造山伸展阶段,尕秀雅平东岩体和红柳沟北岩体正是拉张环境下幔源岩浆活动的产物。在东昆仑地区、柴北缘发现的铜镍矿床和铜镍矿点(除夏日哈木有争议外)基本都形成于晚志留世—晚泥盆世。结合区域成矿年代学研究,认为晚志留世—晚泥盆世期间,东昆仑造山带和祁连造山带之间的柴达木地块、欧龙布鲁克微陆块,以及位于这两大造山带内部的微型古陆块区,是形成岩浆铜镍硫化物矿床和钛铁氧化物矿床的有利环境。  相似文献   

羌塘盆地双湖地区曲色组冷泉碳酸盐岩及其地质意义          下载免费PDF全文

夏国清  伊海生 《沉积与特提斯地质》2015,(1):68-75

羌塘盆地南部双湖地区曲色组地层发育大量碳酸盐岩结核,这些结核多呈丘状、椭球状、透镜状、似层状、脉状、树枝状产出。其物质组分主要为泥微晶碳酸盐矿物,少量粘土矿物、石英及草莓状、半自形黄铁矿等。草莓状黄铁矿平均粒径在5.0μm左右,内部可见葵花状构造。发育凝块状、气孔状和渗漏孔等特殊构造。产双壳类、菊石类、蠕虫状或树枝状生物及超微生物化石,生物密度极高。碳同位素明显负偏,硫同位素则明显正偏,其特征与现代海底天然气水合物的渗漏、释放所形成的冷泉碳酸盐岩机理一致,因而推测为古代海底天然气渗漏喷发形成。大量海底天然气泉口的存在,可能表明羌塘盆地双湖地区早侏罗世大洋缺氧事件与海底天然气水合物喷发存在极大关联。  相似文献   

陕南凤凰岭南缘变质镁铁质—超镁铁质侵入岩矿物学特征——对Fe-Ti成矿作用的指示     

黄杰  覃小锋  王宗起  张英利  杨文  朱安汉  宋炯 《地质通报》2015,(Z1):508-522

陕南凤凰岭南缘变质镁铁质—超镁铁质侵入岩为富含Fe、Ti等有用元素的含矿岩体。利用岩石地球化学方法、偏光显微镜和电子探针技术对该区镁铁质—超镁铁质侵入岩的岩石学、地球化学和矿物学特征进行了研究,并对Fe-Ti氧化物的形成、富集进行了初步探讨,对成岩、成矿作用具有一定的参考意义。结果表明,成矿镁铁质—超镁铁质侵入岩与非成矿镁铁质—超镁铁质侵入岩为不同岩浆源区、同期岩浆作用的产物,镁铁质—超镁铁质侵入岩类的Fe-Ti矿化作用与初始岩浆的源岩之间具有密切关系。Fe-Ti氧化物主要以钛铁矿和榍石的形式存在,局部见少量金红石。化学成分上,钛铁矿具富锰贫镁特征,本区Fe-Ti氧化物的形成和富集过程经历了岩浆结晶分异阶段和热液蚀变阶段。  相似文献   

镁铁质岩,超镁铁质岩陨落成因概论     

张海亭 《长春地质学院学报》1993,23(3):358-359

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