Geophysical prospecting of copper-nickel deposits in Beishan rift zone, Xinjiang

The Beishan rift zone in Xinjiang Uygur Autonomous Region was formed due to strong activities of faults on the basement of the Tarim continental crust.Despite the fact that many geological research results of the rift zone have been achieved,only a few studies have been conducted on its regional geophysical characteristics.In this paper,the gravity and magnetic anomalies of the rift zone were highlighted through specific data processing of 1∶50000 high-precision aeromagnetic data and gravity data with a grid spacing of 2 km×2 km.Based on this,the geophysical evidence for the scope and internal structures of the Beishan rift zone was obtained for the first time.The distinct characteristics of magnetic and gravity fields in the areas to the north and south of the Beishan rift zone reveal that deep faults exist between the Beishan rift zone and the geological units on the southern and northern sides.Furthermore,the faults on the two areas contain the bidirectional thrusts and have flower-shaped structures according to the characteristics of the magnetic and gravity fields.The Beishan rift zone can be divided into two tectonomagmatic zones,namely the Zhongposhan-Bijiashan-Cihai-Baishanliang zone(the northern zone)and the Bayiquan-Qixin-Baishan zone(the southern zone).The northern zone can be further subdivided into three comet-shaped anomaly groups(tectonomagmatic areas),while the southern zone can be further subdivided into two tectonomagmatic areas.According to the characteristics of aeromagnetic anomalies and gravity field,19 mafic-ultramafic complexes were delineated.The known Pobei,Hongshishan,and Qixin complexes are all located within the inferred complexes,with estimates of total explored resources of Ni,Cu,and Au of 3×10^(6) t,10×10^(3) t and 10 t,respectively.The prospecting of high-grade copper-nickel deposits should focus on the periphery and deep parts of the known and inferred mafic-ultramafic complexes.Among them,the peripheral strata of the complexes specifically have great prospecting potential of large-scale high-grade copper-nickel deposits of magma injection type.Finally,this paper analyzed the application effects of the rapid airborne-ground-drilling synergetic exploration method in the prospecting of copper-nickel deposits in Qixin,Beishan,Xinjiang,which will provide references for further exploration of copper-nickel deposits in Beishan area,Xinjiang.

A Genetic Model for Ore Magma of the Chibaisong Copper-Nickel Sulphide Deposit, Jilin

In the early 1980's, the author proposed his view that copper-nickel sulphide deposts are of ore magma origin. For more than ten years, this view has aroused attention of his colleagues at home and abroad. In this paper an attempt is made to deal with the genetic model for ore magma of copper-nickel sulphide deposits in more details on the basis of geological, geochemical, petrophysico - chemical and thermodynamic studies of the Chibaisong copper-nickel sulphide deposit in the Changbai Mountains, Jilin province.

GEOCHEMICAL CHARACTERISTICS OF PLATINUM GROUP ELEMENTS IN JINCHUAN SUPER-LARGE SULFIDE COPPER-NICKEL DEPOSIT, JINCHANG CITY, GANSU PROVINCE, CHINA

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.

高镍铜镍矿床的特征、形成机制与勘查展望

岩浆铜镍矿床100%硫化物中的Ni含量与赋矿岩石和成矿过程紧密相关,记录岩浆成分、分异程度与硫化物演化过程。硫化物异常高镍(高镍硫化物)往往被认为与科马提质岩浆或者后期热液作用密切相关。近年研究结合勘查证实,赋含高镍硫化物的矿床(高镍铜镍矿床)不仅限于科马提岩,还与苦橄质、玄武质岩浆有关,另外,热液富集作用并不是必要因素。本文总结了世界上高镍铜镍矿床的基本特征和形成机制,分析提出了不同机制的判别标志,并展望了其勘查前景。详细对比高镍铜镍矿床的产出环境、赋矿岩相、矿石特征、矿物组合等特征,该类矿床往往产于大陆裂谷和造山带环境,与基性程度较高的岩浆有关,以橄榄岩赋矿为主,含镍硫化物组合主要为镍黄铁矿-磁黄铁矿-黄铜矿组合,少数为针镍矿-镍黄铁矿-黄铁矿组合。科马提岩相关矿床可将Ni含量大于16%的硫化物定义为高镍硫化物,苦橄质-玄武质岩浆相关矿床的硫化物可分为高镍硫化物(Ni>10%)、中镍硫化物(5%～10%)和富铜硫化物(Ni<5%,Cu>Ni)。原生高镍硫化物可由富镍岩浆熔离、硫化物从橄榄石中吸取Ni、硫化物结晶分异、硫化物与硫不饱和岩浆反应等机制形成。苦橄质-玄武质岩浆相关的矿床,硫化物与橄榄石的Fe-Ni交换反应是高镍硫化物形成的重要机制。辉石岩源区地幔部分熔融形成富镍岩浆是否为高镍硫化物形成的必要条件尚存争议。不同机制形成的高镍硫化物具有迥异的岩石-矿物组合和地化特征。硫化物矿物组合、橄榄石成分(Fo值、Ni含量、Fo值-Ni含量的相关性)、伴生元素(铜、铂族元素)丰度-配分模式等特征可作为区分不同高镍硫化物形成机制的有效指标。我国新疆黄山南、坡一和青海夏日哈木矿床(部分浸染状矿化橄榄岩)以赋含高镍硫化物为特征,新疆喀拉通克矿床的硫化物则以富铜为特征,中国其余矿床的硫化物均属中镍硫化物。目前研究指示中国的高镍铜镍矿床与母岩浆相对富镍、硫化物与橄榄石Fe-Ni交换作用密切相关,后者可使硫化物Ni含量提升3%～5%。在铜镍矿床勘查方面,稀疏-中等浸染状高镍硫化物矿石即可达到工业品位,稠密浸染状-块状高镍硫化物矿石可达到很高的Ni品位(10%),是高品位镍矿勘查的一个重要方向。造山带环境富水、相对高氧逸度(可高达QFM+1)的岩浆可能是形成高镍硫化物的有利条件,该环境橄榄石Fo值较高(>87mol%)的岩体有利于形成高镍硫化物。

新疆若羌县坡一岩浆硫化物矿床地质特征及成因初探

坡一岩浆硫化物矿床赋矿岩石主要为华力西中期第一侵入次第二阶段纯橄榄岩、辉石橄榄岩、橄榄辉石岩、辉石岩。镍矿体主要分布于超基性岩体中部、底部。矿石类型以星散浸染状为主,次为稀疏浸染状、少量稠密浸染状、海绵陨铁状,半块状-块状、脉状。金属硫化物主要为镍黄铁矿、磁黄铁矿及黄铜矿,次为黄铁矿、白铁矿。通过对坡一岩浆硫化物矿床岩相学、岩石化学、稀土微量元素特征、成矿作用总结分析,初步探讨矿床成因。

三维技术在新疆若羌坡一镍矿找矿预测中的运用

新疆若羌北山地区坡一镍矿为近期发现、评价的超大型岩浆硫化物型铜镍矿床,目前已查明的镍金属资源量达130万t。由于坡北地区岩浆活动频繁,岩相组成复杂,认为坡一成矿岩体为早二叠形成的复式岩体。通过对坡一镍矿岩相学、岩石学的对比研究,总结出各岩相的时空关系,甄别出主要成矿岩体,并结合各岩相所反映出的地球物理特征,建立了三维地质模型及物理模型。通过对比研究,指明坡一镍矿下一步找矿方向,通过三维预测对找矿远景进行了探讨。

新疆北山坡一镍矿床中钴的赋存状态、地球化学特征及其对钴成矿的启示

钴作为当今社会必需的一种关键矿产资源,岩浆铜镍矿床是我国钴资源供应的重要矿床种类之一,该类矿床中钴元素通常赋存于镁铁质硅酸盐矿物、硫化物、类硫化物和铁氧化物中,然而镁铁质硅酸盐和铁氧化物中的钴难以分选利用,因此钴赋存状态的厘定是铜镍矿床中钴资源评价和利用的重要前提。新疆东天山-北山地区发育大量晚古生代、普遍伴生钴的岩浆铜镍矿床,其中位于北山地区的坡一镍矿床以赋含高镍硫化物为特色,是研究岩浆铜镍矿床中钴元素的赋存状态、分布特征以及钴与镍相互关系的理想对象。坡一镍矿的含矿岩相主要为单辉橄榄岩、纯橄岩和橄长岩,以稀疏浸染状矿化为主,钴主要以类质同象形式赋存于镍黄铁矿,其次为铬尖晶石、橄榄石和磁黄铁矿,少见独立钴矿物。矿物微区原位分析结果显示原生矿物中钴含量由高到低依次为镍黄铁矿(~8404×10^(-6))>>铬尖晶石(~475×10^(-6))>磁黄铁矿(高Ni含量)(~299×10^(-6))>橄榄石(~137×10^(-6))>黄铜矿(~13.0×10^(-6))>磁黄铁矿(低Ni含量)(~8.35×10^(-6))。坡一岩体的蚀变橄榄岩中发育三种产状的次生磁铁矿:蚀变橄榄石裂理中细脉状磁铁矿、铬尖晶石边部环状磁铁矿边、硫化物矿边部和裂隙中次生磁铁矿边。元素面扫描结果显示次生磁铁矿中Co含量明显高于原生硫化物、氧化物和硅酸盐矿物,且显示富Co贫Ni特征。坡一矿床中硫化物和硅酸盐矿物表现出明显的Co-Ni正相关,而铬尖晶石中Co和Ni显示负相关,表明Co^(2+)主要以类质同象形式替代Fe^(2+)进入硫化物和硅酸盐矿物晶格,以替代Fe^(2+)、Ni^(2+)的形式进入铬尖晶石。坡一矿床中Ni和Co的共生行为,主要归因于岩浆演化过程硫化物熔离和硅酸盐矿物分离结晶过程中相近的配分行为,而Ni和Co的离散特征主要受控于铬尖晶石的分离结晶和R值(岩浆和硫化物质量比)的变化、热液蚀变过程中次生磁铁矿Co富集作用。由于铬尖晶石与硅酸盐矿物中的钴难以分选利用,北山地区的钴矿资源勘查应关注贫铬尖晶石、橄榄石镍亏损的富硫化物超镁铁质岩体。

新疆东天山坡一铜镍矿地质特征及找矿远景分析

坡一镍矿位于新疆东天山-北山地区该区属于中亚造山带偏南侧区域的缘头部位的镁铁-超镁铁岩体集中分布区,区内主要发育岩浆铜镍硫化物矿床。岩浆活动(早二叠世)在区内分布非常活跃,镁铁超镁铁杂岩体在该区大量的分布,而且在规模上这些岩体都非常的大,铜镍矿化非常明显,目前红石山以及坡北和蚕东以及罗东和旋窝岭等铜镍矿在区内非常发育。在北山镁铁-超镁铁岩带内,坡一岩体具有非常好的成矿迹象以及成矿潜力。本文对坡一铜镍矿地质特征及找矿远景进行了分析探讨。

新疆若羌县坡一超镁铁岩浆岩型铜镍矿床特征及远景展望

新疆北山裂谷带中出露有数量众多的镁铁-超镁铁岩,坡一铜镍矿位于北山裂谷金铜镍成矿带西部、坡北镁铁-超镁铁岩带西南部。经1989~2014年的持续勘查,坡北岩带中的坡一铜镍矿规模达到100万吨以上。笔者在前人工作的基础上,结合裂谷环境下成岩机制,分析了坡一铜镍矿成矿环境及成矿作用演化特征,树立了独特的多期岩浆成矿模式,建立了找矿标志,为成矿带镁铁-超镁铁岩浆硫化物型铜镍矿床建立了成矿模型,且对成矿远景做了探讨。