机构地区:[1]中南大学有色金属成矿预测教育部重点实验室,长沙410083 [2]中南大学地球科学与信息物理学院,长沙410083 [3]金川集团股份有限公司镍钴研究设计院,金昌737104
出 处:《中国有色金属学报》2015年第3期761-775,共15页The Chinese Journal of Nonferrous Metals
基 金:国家自然科学基金资助项目(41172297)
摘 要:已发现的金川铜镍硫化物矿床产于两条基性-超基性岩墙中,而金川最大的Ⅱ-1、Ⅱ-2两个矿体均位于南东侧的岩墙内。通过分析Ⅱ-1、Ⅱ-2两个矿体矿石的主量元素、稀土元素以及微量元素的特征,探讨二者的母岩浆在岩浆演化过程中的联系与独立性。Ⅱ-1、Ⅱ-2号矿体矿石均属于具有富Mg O(w(Mg O)为10.4%~34.5%)、贫Al2O3(w(Al2O3)为0.67%~15.35%)及K2O(w(K2O)为0.01%~1.42%)特征的铁质(m/f=(Mg2++Ni2+)/(Fe2++Fe3++Mn2+),为1.30~5.16)超基性岩;稀土元素及微量元素配分曲线极为相似,轻重稀土分异明显(Σ(LREE)/Σ(HREE)为3.27~9.63),且大离子亲石元素相对富集,显示Ⅱ-1、Ⅱ-2两个矿体的母岩浆具有强烈的亲源关系。通过一系列反映岩浆演化特征的比值及其相互间的关系,如w(Sm)-w(Sm)/w(Yb)、w(La)/w(Sm)-w(Sm)/w(Yb)、w(Th)N/w(Nb)N、w(Th)/w(Yb)-w(Nb)/w(Th)、w(Mg O+Fe OT)/w(Al2O3)-w(Si O2)/w(Al2O3)(Fe OT为全铁含量)等,得出Ⅱ-1、Ⅱ-2两个矿体的母岩浆均为石榴子石二辉橄榄岩经过30%~40%的分离熔融形成,上升过程中混染了5%~20%的地壳物质。同时,岩浆的结晶分异作用由橄榄石控制,均显示了二者的母岩浆在演化过程中密切的联系;但是Ⅱ-2号矿体矿石的各主量元素的质量分数与w(Mg O)的线性关系较复杂,这与呈明显单一线性关系的Ⅱ-1号矿体不同,暗示二者在岩浆冷凝过程中演化的独立性。因此,Ⅱ-1、Ⅱ-2号矿体的母岩浆本是在同一岩浆通道中演化,受到地壳混染后,在冷凝过程中发生了分离,而后在横向上并列的两个岩浆通道中分别演化并成矿。The discovered Jinchuan Cu-Ni(PGE) sulfide deposit occurs in two ultrabasic dykes, and the two main orebodies in Jinchuan, Ⅱ-1 orebody and Ⅱ-2orebody were outputted in one ultrabasic dyke in Southeastern side. In order to prove the particularity and connection of parental magma of Ⅱ-1 and Ⅱ-2 orebodies during magma evolution, the contents of major elements, REE and trace elements in the two orebodies were measured and compared with each other. The two orebodies belong to iron-ultrabasic rocks(m/f=(Mg2++Ni2+)/(Fe2++Fe3++Mn2+), 1.30-5.16), and have the following features: rich in Mg O(w(Mg O), 10.4%-33.5%), poor in Al2O3(w(Al2O3), 0.67%-15.35%) and K2O(w(K2O), 0.01%-1.42%). The two orebodies have similar REE distribution and trace elements distribution and strongly fractionated REE pattern(Σ(LREE)/Σ(HREE), 3.27-9.63), and enriches LILE relative to HFSE, reflecting that the parental magma of Ⅱ-1 and Ⅱ-2 orebodies have a strongly close relationship. Some trace element ratios and relationship characterizing the magma evolution, such as w(Sm)-w(Sm)/w(Yb), w(La)/w(Sm)-w(Sm)/w(Yb), w(Th)N/w(Nb)N, w(Th)/w(Yb)-w(Nb)/ w(Th) and w(Mg O+Fe OT)/w(Al2O3)-w(Si O2)/w(Al2O3)(Fe OT is total iron content), are suggested that the parental magma of Ⅱ-1 and Ⅱ-2 orebodies are generated by 30%-40% fractional melting of the garnet lherzolite, contaminated by 5%-20% crustal materials during digenetic evolution process and experienced olivine crystallization. This indicates that the parental two kinds of magma of Ⅱ-1 and Ⅱ-2 orebodies have close relation during magma evolution. However, there exists an obvious difference that the Mg O value of Ⅱ-2 orebody shows a more complicated linear relation with other major elements than that of Ⅱ-1 orebody. It suggests that the two kinds of parental magma have experienced independent evolution in their cooling stage. The two kinds of parental magma of Ⅱ-1 and Ⅱ-2 orebodies are original in the same magma conduit, along with the crustal contamination. The two kinds of paren
正在载入数据...
正在载入数据...
正在载入数据...
正在载入数据...
正在载入数据...
正在载入数据...
正在载入数据...