摘要
东宁新城沟地区的花岗岩体位于兴蒙造山带东缘的活动大陆边缘带。通过岩相学和岩石地球化学分析认为,研究区内岩体的里特曼指数δ介于1.41~2.11之间,为钙碱性岩系;w(K2O)/w(Na2O)比值大于1,为高碱相对富钾;铝饱和指数ACNK=1.02~1.20,主要为弱过铝质I型花岗岩,部分具有S型同碰撞花岗岩的特征。岩体中稀土总量较低(∑REE=72.35×10-6~217.64×10-6),轻、重稀土分异较强(LaN/YbN=2.74~11.37),Eu具有较为明显的负异常,δCe为0.96~1.11,Ce异常不明显;Nb、Ta、P、Ti等相对亏损,Rb、Ba、K等相对富集,w(Nb)/w(Ta)比值为(6.18~26.33,平均为15.18)小于16.2,指示岩浆来源于上地幔或下地壳,形成过程中同化混染了较多壳源物质。区内岩浆的形成受古生代末和中生代初西伯利亚板块与华北板块发生陆陆碰撞以及晚三叠世古太平洋板块向欧亚大陆东缘俯冲的双重作用影响,岩浆侵入存在由早期向晚期阶段演化的过程,致使源岩存在一定差异,具有多期次、多阶段、复合成因的特点。物化探异常、岩石地球化学及含矿性参数显示,研究区具有寻找浅成低温热液型Au、Ag、Cu矿的资源潜力。
The granites in Xinchenggou area of Dongning County are located on the active continental margin of eastern part of Xing'anling-Mongolian orogenic belt. In this paper,petrologic and element geochemical studies were carried out for granites in Xinchenggou area,Dongning County. Major element geochemistry shows that the rocks are calc-alkaline and I-type granites,and are also characterized by enrichment of alkali,relative enrichment of potassium and S-type syn-collisional granites. The Rittman index δ is from 1.41 to 2.11.The alumina saturation index ACNK is from 1.02 to 1.20. REE concentrations are low(ΣREE = 72.35×10-6~ 217.64×10-6) and show obvious differentiation between LREE and HREE(LaN/YbN= 2.74 ~ 11.37),with apparent Eu negative anomalies(δEu = 0.14 ~ 0.83),and the abnormality of δCe(δCe = 0.96~1.11) is not apparent. In addition,the rock mass is relatively poor in such elements as Nb,Ta,P and Ti,and rich in Rb,Ba and K. w(Nb)/w(Ta) ratios of trace elements are less than 16.2,suggesting that the magmas were formed by partial melting of the crust. The magmas were formed by collision between the North China plate and Siberia plate in Late Paleozoic-Early Mesozoic period and subduction of the paleo-Pacific plate towards the east edge of Eurasia in Late Triassic. The magmas also had the characteristics of multi-stages and complex genesis. Geophysical and geochemical anomaly,geochemical characteristics,and geochemical ore parameters indicate that this area has prospecting potential for epithermal-type Au-Ag-Cu deposits.
作者
郝义
王显民
王金香
HAO Yi;WANG Xian-Min;WANG Jin-Xiang(No. 1 Prospecting Party of Shandong Coal Geology Bureau, Tengzhou 277500,China)
出处
《物探与化探》
CAS
CSCD
北大核心
2018年第3期461-472,共12页
Geophysical and Geochemical Exploration
基金
山东省国土资源厅地勘基金项目(鲁勘字(2015)58号)
关键词
新城沟地区
活动大陆边缘
花岗岩
地球化学特征
资源潜力
Xinchenggou area
active continental margin
granite
geochemical characteristics
resource potential