甘肃北山和金川与铜镍矿床有关的超基性岩与全球板内环境超基性岩的对比:大数据研究的初步结果

Comparison of the ultrabasic rocks associated with Cu-Ni deposits in Beishan and Jinchuan,Gansu Province and those associated with within-plate environment:preliminary results of big data research

在收集甘肃北山和金川地区与铜镍硫化物矿床有关的超基性岩数据的基础上,与GEOROC和PetDB两个数据库中的全球板内超基性岩数据进行对比,发现甘肃北山、金川地区与铜镍有关的超基性岩与全球板内超基性岩各元素平均值较接近(除稍富集LILE之外),而北山地区以高的Th/Nb和富集HREE与金川区分,同时Cu、Cs、Nb、Ta、Rb/Nb、CaO/REE等元素或元素比可作为甘肃北山和金川地区超基性岩是否含矿的重要地球化学标志。皮尔逊相关系数研究表明,虽然甘肃北山和金川地区与铜镍硫化物矿床有关的超基性岩的产出位置、形成时代及源区特征均不同,但是具有很高的地球化学相关性,而WPU(板内超基性岩)与WPUT(大陆溢流、大陆裂谷和板内超基性岩合并)及WPU中坐标值相近的数据相关性较差。WPUT内部本身相似性极差,但其平均值却与甘肃北山和金川地区的超基性岩相似性极高。同时,笔者选取了白石泉、石西、葫芦、黄山东等26个与铜镍硫化物矿床有关的超基性岩数据,与甘肃北山、金川铜镍硫化物矿床有关的超基性岩数据进行比对,整体显示出极高的相关性。因此我们推断与铜镍硫化物矿床有关的超基性岩在形成过程中虽受到其他地质作用的改造,但总体上具相似的地球化学特征。

In this study,we collected data on the ultrabasic rocks related to Cu-Ni ore in Beishan and Jinchuan,Gansu Province and compared with that of the global intra-plate ultrabasic(WPU)rock collection in the GEOROC and PetDB databases.We found that in Beishan and Jinchuan ultrabasic rocks,the average elemental contents related to Cu-Ni were close to that of WPU(except for the slightly enriched LILE).Therefore,elements Cu,Cs,Nb and Ta or elemental pairs Rb/Nb,CaO in ultrabasic rocks can be used as important geochemical prospecting indicators for the Beishan and Jinchuan ultrabasic ore deposits.Beishan is distinguished from Jinchuan by high Th/Nb ratio and HREE enrichment.Our Pearson correlation coefficient study further indicated that the two ultrabasic rocks have different distribution,formation age and source area characteristics but are highly correlated geochemically,whereas for total WPU(WPUT)or WPU of similar coordinates the correlation is relatively poor.However,despite extremely low geochemical similarity for WPUT,the average geochemical characteristics of WPU is similar to the Beishan and Jinchuan ultrabasic rocks.Meanwhile,we examined the data of 26 basic-ultrabasic rocks related to Cu-Ni sulfide deposits in the areas of Baishiquan,Shixi,Hulu,east of Huangshan,etc.,and compare them with that of basic-ultrabasic rocks associated with the Beishan and Jinchuan Cu-Ni sulfide deposits in Gansu.We found still an extremely high overall correlation.Therefore,we conclude that the ultrabasic rocks associated with Cu-Ni sulfide deposits share some geochemical similarities provided with modifications by other effects during the formation processes.