摘要
近年来,成矿斑岩岩浆的氧化状态对斑岩铜矿床成矿潜力和成矿规模的控制作用受到了矿床学家的广泛关注。文章总结了斑岩型铜矿床成矿斑岩岩浆氧化状态的主要研究方法及各自的适用条件:(1)钛铁氧化物(钛铁矿-磁铁矿)固熔体的组成,适用于含共生岩浆成因钛铁矿-磁铁矿的斑岩体;(2)岩石中的Fe^(3+)/Fe^(2+)含量比值,适用于新鲜的熔融包裹体或未发生热液蚀变和地表风化作用的新鲜岩石;(3)黑云母中的Fe^(3+)、Fe^(2+)和Mg含量,适用于黑云母与磁铁矿和钾长石共生的岩体;(4)角闪石主量元素含量,适用于温度为550～1120℃、压力<1200 MPa、氧逸度(f(O2))为-1≤ΔNNO≤+5的钙碱性喷出岩或浅成侵入岩;(5)锆石Ce^(4+)/Ce^(3+)比值;(6)锆石EuN/EuN*比值,斑岩铜矿成矿斑岩为中酸性岩体,其中锆石普遍发育,因此被广泛用于确定岩浆氧化状态。文章还通过收集中国冈底斯成矿带、金沙江-红河成矿带、中甸岛弧成矿带、环太平洋成矿域和中亚成矿域主要斑岩铜矿床成矿斑岩岩浆氧逸度资料,讨论岩浆演化状态对斑岩型铜矿床成矿作用和成矿规模的控制作用,发现同一成矿带内含矿斑岩的氧化状态明显高于不含矿斑岩,且含矿斑岩的氧化状态与斑岩铜矿床的成矿规模具有正相关性。
In recent years, the constraint of magma oxidation state on mineralization potential and scale of porphyry copper deposits has attracted lots of earth scientists＇ attentions. This paper summarized main methods for estima- ting magma oxidation state of porphyry copper deposits and their applied conditions. These methods are： ① II- menite-magnetite oxygen barometer, which is used in the conditions that ilmenite coexists with magnetite and Fe- Ti oxides have homogeneous chemical compositions; ② Whole-rock Fe3＋/Fe2＋ ratio, it can only be used on fresh melt inclusions or igneous rocks devoid of hydrothermal alteration or surficial weathering; ③Biotite component, which coexists with magnetite and potassium feldspar; ④ Amphibole oxygen barometer, which is used with calcalkaline volcanic or hypabyssal intrusive rocks with temperatures of 550-1120℃, pressure of 1200 MPa, and oxygen fugacity of -1≤ANNO≤〈＋5; ⑤ Zircon Ce4＋/Ce3＋ ratios, and ⑥ Zircon EuN/EuN＊ ratios, which are recently popularly used, because zircon is a common accessory mineral in intrusions related to porphyry deposits. On these bases, the magma oxidation state data of porphyry deposits in Gangdese, Jinsha river-Red river, Zhongdian island arc, Circum-Pacific and Central Asian metallogenic belts are collected to discuss the constraint of magma oxidation state on mineralization potential and scale of porphyry deposits. In most metallogenic belts, the ore- bearing intrusions have higher oxidation state than barren intrusions, and the higher oxidation state is also favo- rable to the formation of large scale porphyry copper deposit.
作者
张京渤
安芳
ZHANG JingBo;AN Fang(State Key Laboratory of Continental Dynamics,Department of Geology,Northwest University,Xi＇an 710069,Shaanxi,China)
出处
《矿床地质》
CAS
CSCD
北大核心
2018年第5期1052-1064,共13页
Mineral Deposits
基金
陕西省教育厅科技计划项目(批准号:14KJ1761)
国家自然科学基金项目(批准号:41403033)的联合资助
