【摘要】 红山铜多金属矿床是义敦岛弧南端规模最大的矽卡岩型铜矿床。矽卡岩矿物以石榴子石为主,多以粒状或粒状集合体产出,偶见与透辉石共生。根据穿插关系及光学特征,将该矿床的石榴子石分为早（Grt I）、晚（Grt II）两个世代。本文利用电子探针和LA-ICP-MS原位微区分析技术对两类石榴子石开展了系统研究。石榴子石的SiO₂含量为34. 47%～36. 29%、Ca O含量为32. 48%～34. 59%、FeO含量为20. 58%～28. 17%、Al₂O₃含量为0. 01%～5. 39%,计算获得其属于钙铁榴石-钙铝榴石系列（Gro1-29And69-98）。Grt I较Grt II更富钙铁榴石组分,而Grt II更多发育振荡环带。石榴子石稀土元素总量较低(ΣREE=8. 72×10^-6～368×10^-6)、轻重稀土元素分异明显（LREE/HREE=2. 13～3104）、多正Eu异常（δEu=0. 53～13. 6）。亏损Rb、Ba和Sr等大离子亲石元素(Rb=0. 02×10^-6～3. 75×10^-6,Ba=0. 01×10^-6～0. 74×10^-6,Sr=0. 01×10^-6～3. 23×10^-6),富集Th、U和Zr等高场强元素(Th=0. 01×10^-6～27. 8×10^-6,U=0. 83×10^-6～98. 7×10^-6,Zr=0. 03×10^-6～175×10^-6)。Grt II的稀土元素总量、LREE/HREE比值、δEu值、Y和U含量总体高于Grt I。石榴子石主量和微量元素含量及变化特征表明,矽卡岩化早期的流体为相对封闭、酸性、氧逸度较高的体系,热液扩散交代作用占主导,多形成无环带的石榴子石;而晚期,流体演化为相对开放、弱酸性-中性、氧逸度相对较低的体系,渗滤交代作用占主导,多形成振荡环带发育石榴子石。此外,石榴子石中较高的Zn含量(Zn=1. 42×10^-6～37. 2×10^-6)说明成矿流体富集Zn,可能暗示了一定的锌成矿前景。更多还原

【Abstract】 The Hongshan skarn copper deposit is located in the south of Yidun island arc. The skarn minerals mainly include granular garnets with oscillation zoning,which occasionally coexist with minor diopside. According to their cutting relationship and optical characteristics,the garnets in the deposit can be divided into the early（ Grt I） and the late（ Grt II） generations. In this study,the two kinds of garnets were analyzed via electron probe and LA-ICP-MS in situ microanalysis technology. The results show that they have SiO₂,CaO,FeO and Al₂O₃ contents of 34. 47% ～ 36. 29%,32. 48% ～ 34. 59%,20. 58% ～ 28. 17% and 0. 01% ～ 5. 39%,respectively; and the calculated end-members of the garnets suggest they belong to the andradite-grossularite series（ Gro1-29 And69-98）.The Grt I has more andradite endmember than the Grt II,while the later presents more oscillatory zonation. The garnets have relatively low REE contents( ΣREE = 8. 72 × 10^-6～ 368 × 10^-6),high LREE/HREE values（ 2. 13 ～ 3104）,and dominantly positive Eu anomalies（ δEu = 0. 53 ～ 13. 6）. All samples are strongly depleted of large ion lithophile elements,including Rb( 0. 02 × 10^-6～ 3. 75× 10^-6),Ba( 0. 01 × 10^-6～ 0. 74 × 10^-6) and Sr( 0. 01 × 10^-6～ 3. 23 × 10^-6),and enriched in such high field strength elements as Th( 0. 01 × 10^-6～ 27. 8 × 10^-6),U( 0. 83 × 10^-6～ 98. 7 × 10^-6) and Zr( 0. 03 × 10^-6～ 175 × 10^-6). In comparison,theΣREE,LREE/HREE ratios,δEu value,Y and U contents of Grt II are generally higher than those of Grt I. The contents and variation characteristics of major and trace elements in garnets indicate that the fluids in the early stage of skarnization belong to a relatively closed system with acidic and high oxygen fugacity,and hydrothermal diffusive metasomatism is dominated in this system,mainly resulting in garnets without zones（ Grt I）. In the late stage of skarnization,the fluids evolve into a relatively open system,with weak acidic-neutral and low oxygen fugacity,where inltration metasomatism dominates and forms more garnets with oscillating zones（ Grt II）. In addition,the relatively high Zn contents( 1. 42 × 10^-6～ 37. 2 × 10^-6) in the garnets suggest that the ore-forming fluid system is Zn-rich,which indicates the zinc metallogenic prospect in the Hongshan ore district.更多还原