Oxidation Condition and Metal Fertility of Granitic Magmas: Zircon Trace-Element Data from Porphyry Cu Deposits in the Central Asian Orogenic Belt
Oxidation Condition and Metal Fertility of Granitic Magmas: Zircon Trace-Element Data from Porphyry Cu Deposits in the Central Asian Orogenic Belt
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DOI：
10.2113/econgeo.110.7.1861
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发表时间：
2015-11
期刊：
影响因子：
5.8
通讯作者：
P. Shen;K. Hattori;H. Pan;S. Jackson;E. Seitmuratova
中科院分区：
文献类型：
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作者：
P. Shen;K. Hattori;H. Pan;S. Jackson;E. Seitmuratova
中亚造山带 (CAOB) 蕴藏着许多斑岩铜矿床，全部与钙碱性花岗岩相关，尺寸从巨型到小型不等。对哈萨克斯坦博兹沙科尔、努尔卡兹甘、孔拉德、博利、阿克托盖、阔克赛、中国包古图、土乌-延东、蒙古额尔登特等9个斑岩铜矿床（铜含量0.6～12Mt）的13个含矿侵入体进行了全岩和锆石晶粒的主量和微量元素成分测定。所有锆石晶粒均显示出较高的 Ce 4+ /Ce 3+ 比率，范围为 29 至 592。在给定的结晶温度下，来自具有较大 Cu 吨位的沉积物的较高 Ce 4+ /Ce 3+ 比率被记录。大型 (>4 Mt Cu) 和中型 (1.5–4 Mt Cu) 斑岩铜矿床与花岗岩侵入体有关，花岗岩侵入体含有 Ce 4+ /Ce 3+ 比率大于 120 的锆石。计算的 log (f O 2 ) 值与矿床大小之间也存在明显的关系，NNO + 2 值将大型和中型斑岩矿床与小型矿床分开。含矿侵入体岩浆中锆石Ce 4+ /Ce 3+ 比率和相关氧逸度值数据表明，更多氧化岩浆与更大斑岩铜矿床的形成有关。这一结论可能适用于中亚造山带斑岩铜矿的区域勘探。
The Central Asian Orogenic Belt (CAOB) hosts a number of porphyry Cu deposits, all associated with calc-alkaline granitic rocks and ranging in size from giant to small. Major- and trace-element compositions of whole rocks and zircons grains were measured from 13 ore-bearing intrusions in nine porphyry Cu deposits (with 0.6 to 12 Mt Cu), including Bozshakol, Nurkazghan, Kounrad, Borly, Aktogai, and Koksai in Kazakhstan, Baogutu, and Tuwu-Yandong in China, and Erdenet in Mongolia. All zircon grains show high Ce 4+ /Ce 3+ ratios, ranging from 29 to 592. Higher Ce 4+ /Ce 3+ ratios are recorded at a given crystallization temperature from deposits with larger Cu tonnages. Large (>4 Mt Cu) and intermediate (1.5–4 Mt Cu) size porphyry Cu deposits are associated with granitic intrusions that have zircons with Ce 4+ /Ce 3+ ratios greater than 120. There is also a clear relationship between calculated log ( f O 2 ) values and the size of deposits, with NNO + 2 values separating large and intermediate porphyry deposits from small deposits. The data of zircon Ce 4+ /Ce 3+ ratios and associated oxygen fugacity values in magma from ore-bearing intrusions indicate that more oxidized magmas are associated with the formation of larger porphyry Cu deposits. Such a conclusion may potentially be used in regional exploration for porphyry Cu deposits in the CAOB.