摘要
对雄村斑岩矿集区新发现的Ⅲ号矿体开展了斑岩体锆石LA—ICP—MS U—Ph年龄、原位Hf同位素以及微量元素分析，结果显示：Ⅲ号矿体的角闪石英闪长玢岩与石英闪长斑岩侵位时代相近，分别为（171．2±2．2）Ma（1σ，MSWD=2．5）和（171．0±1．9）Ma（1d，MSWD=1．8），形成时代与I号和Ⅱ号矿体中的斑岩体类似；角闪石英闪长玢岩的（176Hf／177Hf）i介于0．282959～0．283162之间，εHf（t）介于10．217～17．436之间，二阶段模式年龄为95～559Ma；石英闪长斑岩（176Hf／177Hf）i介于0．282949-0．283123之间，εHf（t）为10．015～16．207，二阶段模式年龄为220～577Ma。锆石原位Hf同位素结果表明角闪石英闪长玢岩与石英闪长斑岩的源区为亏损地幔，与新特提斯洋向北俯冲的岛弧环境有关。角闪石英闪长玢岩、石英闪长斑岩的锆石U—Pb年龄与结晶温度T，及与Yb／Nd、Nb／Ta、Th／U比值的关系显示，起源于亏损地幔的岩浆上涌过程中并没有经历过岩浆混合以及同化混染作用，同时石英闪长斑岩晚期阶段明显比角闪石英闪长玢岩的Th／U比值增长范围大，这可能与石英闪长斑岩岩浆更富含水，并出溶较多的流体有关，而岩浆一流体演化过程暗示着石英闪长斑岩与矿化关系更为密切，这与地质观察事实相符。
This paper reports the LA-ICP-MS zircon U-Pb age, Lu-Hf isotopic compositions and trace elements geochemistry of zircons from No. III orebody of the Xiongcun porphyry copper-gold deposit. The results show that the ages of hornblende quartz diorite porphyrite and quartz diorite porphyry are （171.2 ± 2.2） Ma （MSWD= 2.5） and （171.0 ± 1.9） Ma （MSWD= 1.8） respectively, which are similar to the intrusion ages of No. I orebody and No. II orebody. The zircon Hf isotopic compositions of hornblende quartz diorite display （176Hf/177Hf）i values ranging from 0. 282 959 to 0. 283 162, and εHf（t） values ranging from 10. 217 to 17. 436 with two-stage model ages being 95-559 Ma. The zircon Hf isotopic compositions of quartz diorite porphyrite display （176Hf/177Hf）i values ranging from 0.282 949 to 0.283 123, and εHf（ t ） values ranging from 10. 015 to 16.207 with two stage model ages being 220--577 Ma. The results indicate that the magma was derived from depleted mantle. The petrogenesis of intrusions was related to the Neo-Tethyan oceanic slab subduction towards the southern margin of the Asia Plate. U-Pb age and Tz, Yb/Nd, Nb/Ta, Th/U diagrams show that the magma hasn＇t experienced magma mixing and assimilation process. The Th/U increasing range of the late stage quartz diorite porphyry is higher than that of hornblende quartz diorite porphyrite, suggesting that the quartz diorite porphyry was more rich in fluid and more closely related to mineralization. The results agree with the geological observations.
出处
《矿床地质》
CAS
CSCD
北大核心
2014年第2期361-372,共12页
Mineral Deposits
基金
国家自然科学基金(编号:41172077)
西藏大型矿床成矿专属性研究(编号:1212011221073)共同资助
