藏南努日铜-钨-钼矿床晚白垩世石英闪长岩U-Pb定年及其地球化学特征

董随亮; 黄勇; 李光明; 张丽; 黄瀚霄; 张晖

doi:10.15898/j.cnki.11-2131/td.2015.06.017

藏南努日铜-钨-钼矿床晚白垩世石英闪长岩U-Pb定年及其地球化学特征

中国地质调查局成都地质调查中心, 四川成都 610081

基金项目: 中国地质调查局地质调查项目——西藏扎西康地区铅锌矿调查评价(12120113036000);西藏扎西康铅锌多金属矿整装勘查区专项填图与技术应用示范(1212011221073)

详细信息

作者简介: 董随亮, 工程师, 主要研究方向为矿床学. E-mail:dongsuiliang@163.com.

通讯作者: 黄勇, 博士, 工程师, 主要研究方向为矿床学与成矿规律. E-mail:yong.huang@hotmail.com.

中图分类号: P588.122;P597.3

收稿日期: 2014-04-03

修回日期: 2015-11-07

录用日期: 2015-11-10

刊出日期: 2015-06-25

LA-ICP-MS Zircon U-Pb Dating and Geochemistry of Late Cretaceous Quartz Diorite in the Nuri Cu-Mo-W Deposit, South Tibet

Chengdu Geological Survey Center, China Geological Survey, Chengdu 610081, China

More Information

Corresponding author: HUANG Yong, yong.huang@hotmail.com

Received Date: 03 April 2014

Revised Date: 07 November 2015

Accepted Date: 10 November 2015

Publish Date: 25 June 2015

摘要

摘要:
藏南努日矿床位于冈底斯成矿带南缘, 前人获得的辉钼矿Re-Os同位素年龄为23 Ma, 与明则和程巴矿床成矿时代一致, 但矿区内至今未发现与矿化有关的成矿斑岩体。本文报道了努日矿区新发现的与矿化关系密切的石英闪长岩的地球化学特征, 获得石英闪长岩的LA-ICP-MS锆石U-Pb年龄为93.42±0.76 Ma, 与同一成矿带内桑布加拉和克鲁铜金矿成矿时代一致(90~93 Ma), 表明矿区可能存在两期成矿事件。石英闪长玢岩的主量微量元素SiO₂含量为57.19%~58.23%, A1₂O₃含量为15.78%~16.03%, MgO含量为4.74%~5.32%, Mg^#指数为65.2~67.3;富集大离子亲石元素(Rb、Sr、Ba、U等)及轻稀土元素, 亏损高场强元素, 显示出埃达克岩特征。研究表明石英闪长玢岩形成于洋壳俯冲阶段的弧岩浆岩, 洋壳熔融形成的母岩浆侵入近地表形成早期铜多金属矽卡岩矿化。晚白垩世成矿事件的发现进一步佐证了研究区存在两期矿化叠加事件, 拓展了研究区找矿方向。
- 藏南努日铜-钨-钼矿床 /
- 石英闪长岩 /
- LA-ICP-MS U-Pb定年 /
- 洋壳俯冲
Abstract:
The Nuri deposit is located at the south margin of the Gangdese metallogenic belt in Tibet. Its mineralization age revealed by Re-Os dating of molybdenite is 23 Ma, which is consistent with that of the Mingze and Chengba deposits. However, the ore-related rocks have not yet been identified. In this study, we report the age and geochemistry of the newly discovered quartz diorite related to mineralization. LA-ICP-MS zircon U-Pb dating indicates that the diorite intruded at 93.42±0.76 Ma. The age is consistent with the ages of Shangbujiala(93 Ma) and Kelu(90 Ma) copper-gold deposits in the same metallogenic belt. These ages and previous ages indicate a two-stage ore-forming process. Major elemental analysis shows that quartz diorites contain 57.19%-58.23% SiO₂, 15.78-16.03% A1₂O₃, and 4.74%-5.32% MgO, with Mg^# indicators of 65.2-67.3. Trace element composition suggests that these rocks are rich in large ion lithophile elements and light rare earth elements, but are poor in high field-strength elements, characteristic of adakite. This study indicates that quartz diorites are arc magmatic rocks formed in the stage of oceanic crust subduction. The primary magma formed by melting of oceanic crust intruded at the shallow crust, resulting in the formation of early skarn copper deposit. The identification of two stages of mineralization in the Nuri deposit expands the prospecting direction of the study area.
- Nuri Cu-Mo-W deposit in South Tibet /
- quartz diorite /
- LA-ICP-MS U-Pb dating /
- subduction of oceanic crust

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图 1 区域地质简图(据文献[5]修改)

Figure 1.

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图 2 努日石英闪长岩锆石U-Pb谐和图

Figure 2.

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图 3 (a)努日石英闪长岩的原始地幔标准化微量元素蛛网图; (b)球粒陨石标准化稀土元素配分图; (c)~(d):(Sr/Y)-Y和(La/Yb)_N-Yb_N判别图解(底图据Defant等^[11]。

Figure 3.

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表 1 石英闪长岩锆石U-Pb同位素年龄分析结果

Table 1. Zircon U-Pb isotope data of quartz diorite

测量点号	Pb含量 (×10^-6)	Th含量 (×10^-6)	U含量 (×10^-6)	Th/U	²⁰⁷Pb/²⁰⁶Pb		²⁰⁷Pb/²³⁵U		²⁰⁶Pb/²³⁸U		²⁰⁷Pb/²⁰⁶Pb		²⁰⁷Pb/²³⁵U		²⁰⁶Pb/²³⁸U
测量点号	Pb含量 (×10^-6)	Th含量 (×10^-6)	U含量 (×10^-6)	Th/U	比值	1σ	比值	1σ	比值	1σ	年龄 (Ma)	1σ	年龄 (Ma)	1σ	年龄 (Ma)	1σ
LB-5-01	2.65	121	134	0.902964	0.05248	0.00611	0.10171	0.01309	0.01406	0.00035	307	240	98	12	90	2
LB-5-02	1.94	77.5	92.9	0.833778	0.07416	0.00840	0.15157	0.01927	0.01482	0.0004	1046	225	143	17	95	3
LB-5-03	12.38	735	574	1.280539	0.04932	0.00239	0.09893	0.00495	0.01469	0.00018	163	105	96	5	94	1
LB-5-04	3.49	195	161	1.20958	0.04607	0.00359	0.09204	0.00821	0.01449	0.00034	2	152	89	8	93	2
LB-5-05	2.67	109	139	0.784713	0.03861	0.00495	0.07756	0.0101	0.0149	0.00034	-372	232	76	10	95	2
LB-5-06	5.58	372	251	1.484033	0.05125	0.00384	0.09678	0.00743	0.01437	0.00024	252	159	94	7	92	2
LB-5-07	6.17	423	272	1.556396	0.05429	0.00325	0.10662	0.0066	0.01458	0.00023	383	127	103	6	93	1
LB-5-08	4.08	176	214	0.824164	0.05688	0.00408	0.1071	0.00794	0.01409	0.00026	487	151	103	7	90	2
LB-5-09	4.03	180	203	0.884685	0.05066	0.00364	0.10033	0.00747	0.01499	0.0003	226	152	97	7	96	2
LB-5-10	5.37	249	264	0.94481	0.05502	0.00402	0.10741	0.00816	0.0148	0.00031	413	155	104	7	95	2
LB-5-11	3.70	144	197	0.731058	0.04936	0.00388	0.09898	0.00803	0.01472	0.0003	165	164	96	7	94	2
LB-5-12	4.11	172	214	0.805408	0.05894	0.00422	0.11755	0.00873	0.01471	0.00028	565	149	113	8	94	2
LB-5-13	2.39	118	111	1.066502	0.04717	0.00716	0.09009	0.01506	0.01385	0.00042	58	256	88	14	89	3
LB-5-14	4.09	140	134	1.050307	0.11557	0.01609	0.32843	0.05582	0.01662	0.00058	1889	257	288	43	106	4
LB-5-15	4.98	217	255	0.850507	0.05218	0.00371	0.10328	0.00758	0.01498	0.00028	293	152	100	7	96	2
LB-5-16	7.02	325	349	0.930867	0.05361	0.00295	0.10637	0.00608	0.01452	0.00022	355	118	103	6	93	1
LB-5-17	1.53	59.6	77.2	0.772481	0.06746	0.01083	0.13477	0.02322	0.01449	0.00045	852	330	128	21	93	3
LB-5-18	4.98	297	229	1.295082	0.06229	0.00426	0.12415	0.00873	0.01468	0.00024	684	139	119	8	94	2
LB-5-19	5.52	319	255	1.252934	0.05441	0.00382	0.10935	0.00791	0.01476	0.00026	388	150	105	7	94	2
LB-5-20	2.60	106	130	0.812055	0.07417	0.00567	0.14473	0.01164	0.01466	0.00037	1046	147	137	10	94	2

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