摘要
陈家杖子金矿是赤峰南部地区新发现的隐爆角砾岩型金矿床,矿体呈脉状产于隐爆角砾岩筒内,角砾岩筒主要由隐爆含角砾岩屑晶屑凝灰岩组成。角砾岩筒蚀变强烈,并具一定的蚀变分带,金矿化主要与硅化和冰长石化有关,载金矿物主要为毒砂。含矿岩石的岩石化学特征为铝过饱和型,以w(K2O)>>w(Na2O)为特征,属于钙碱性系列I型花岗岩;稀土元素特征表现为轻稀土元素富集型,有Eu亏损;微量元素具有明显的Ti、Nb、Sr、Ba、Th、U亏损,K富集,与大陆边缘正常弧非成熟花岗岩的微量元素特征相符。石英内流体包裹体均一温度表明,金成矿作用主要发生在150～180℃、225～390℃温度段,估算成矿压力为72×105～158×105Pa(255～560m)。矿石硫同位素组成稳定,δ34SV_CDT变化范围为5.3‰～9.4‰。矿石铅与含矿角砾岩的铅同位素组成相似,μ值分别为7.89～8.16及7.89～8.08,模式年龄为591～622Ma和478～912Ma;在Z_D演化模式图上,岩(矿)石铅投影于上地幔与下地壳演化线之间。含矿角砾岩和二长花岗斑岩脉的ISr为0.70820～0.70118,εSr(t)为50.64～106.8,143Nd/144Nd(t)为0.511819～0.512001,εNd(t)为-7.99～-11.62,具有大陆地壳特征。tCHUR及tDM值与该区晚中生代玄武岩、安山岩一致,而不同于印支期闪长岩及其下地壳麻粒岩包体。硫、铅、锶、钕同位素特征显示,成矿物质具壳幔混源特点。主要含矿角砾岩的Rb_Sr同位素等时线年龄为191Ma,两期隐爆角砾岩之间侵入的二长花岗斑岩脉的等时线年龄为177Ma。陈家杖子金矿应为与早燕山期隐爆角砾岩有关的浅成中_低温热液型金矿床。
The Chenjiazhangzi gold deposit is a newly discovered ore deposit in Chifeng, whose veinlike gold orebodies occur in cryptoexplosive breccia pipes consisting of felsic cryptoexplosive breccia-bearing crystal fragments, lithic fragment tuff, and minor black cryptoexplosive breccia. In this paper, geological and geochemical characteristics of the ore deposit are studied in detail, and its genesis and material source are discussed on the basis of fluid inclusion and isotope studies of the gold ores and ore-bearing rocks. The breccia pipe has been intensely altered and shows apparent alteration zoning. Gold mineralization is closely related to silication and adularization. Electrum is the dominant gold mineral and mainly occurs in arsenopyrite, the dominant gold-carrier mineral. The major oxide of ore-bearing breccia belongs to aluminum supersaturated calc-alkaline Ⅰ-type granite and is characterized by K2O≥Na2O. The primary mantle-normalized rare earth and trace element patterns of the breccia show the enrichment of LREE, K and the depletion of Eu, Ti, Sr, Ba, Th, U, which is in conformity with the features of non-mature normal arc granites on the continental margin. The homogenization temperatures of fluid inclusions in quartz suggest that gold mineralization mainly took place at temperatures of 150-180℃, 225-390℃, and that the estimated ore-forming pressures are about （72-158）×10^5 Pa（255 - 560 m）. The sulfur isotope composition of the gold ores is within the range of 5.3‰-9.49‰ δ^34SV-CDT. The lead isotope composition of ores and that of ore-bearing breccia are similar to each other, their μ values are in the range of 7.89-8.16, 7.89-8.08, and the mode ages are 591-622 Ma and 478-912 Ma, respectively. The lead composition of ores is located at the area between upper mantle and crust evolution lines in the ^207Pb/^204Pb-^206Pb/^204pb diagram. Isr, εSr（t）, ^143Nd/^144Nd（t）, εNd（t） of the ore-bearing breccia and monzonitic granite porphyry are in the range of 0. 7082-0. 70118, 50.64-106.8, 0. 511819-0. 512001, and - 7.99-11.62, respectively, suggesting that they are derived from the continental crust, tCHUR, tDM values of the ores and ore-bearing breccia are similar to those of Late Mesozoic basalt and andesite, but different from the data of Early Mesozoic diorite and lower crust xenolith outside the ore deposit. Characteristics of S, Pb, Sr, Nd isotopes indicate that ore-forming materials are mainly derived from the crust, with some probably from the mantle. The Rb-Sr isochron age of early ore-bearing breccia is 191 Ma, and the age of monzonitic granite porphyry emplaced after the early breccia pipe is 177 Ma. The Chenjiazhangzi gold deposit is of the epithermal-mesothermal type formed in Early Yanshanian period.
出处
《矿床地质》
CAS
CSCD
北大核心
2005年第4期373-387,共15页
Mineral Deposits
基金
地质调查项目(D002_028_05)的资助
关键词
地球化学
金矿床
隐爆角砾岩
成矿作用
陈家杖子
赤峰
内蒙古
geochemistry, gold deposit, cryptoexpolsive breccia, ore-forming process, Chenjiazhangzi,Chifeng, Inner Mongolia
