西藏错那洞穹隆祥林铍锡多金属矿地质特征及找矿方向

doi:10.13745/j.esf.sf.2021.8.30

摘要/Abstract

摘要：

错那洞穹隆是北喜马拉雅片麻岩穹隆带(NHGD)中发现的新成员,穹隆由核-幔-边3部分组成。核部由寒武纪花岗质片麻岩组成,幔部由早古生代云母片岩和夕卡岩化大理岩组成,边部由变质沉积岩组成。在穹隆核部后期侵入有淡色花岗岩和伟晶岩脉。祥林铍锡多金属矿位于错那洞穹隆北部,矿区内发育多条南北向、北东向张性断裂。通过系统的地表工程控制,在穹隆幔部和断层破碎带内新发现了铍锡多金属工业矿体。通过错那洞穹隆北部祥林矿区的解剖,矿化类型可初步划分为夕卡岩型、锡石-石英脉型、锡石-硫化物型和花岗伟晶岩型。夕卡岩型矿体赋存在穹隆幔部的夕卡岩化大理岩内,矿化以铍、锡、钨为主,锡品位变化较大。锡石-石英脉型矿体受北东向张性断裂控制,矿化以锡、铍、钨为主,矿石品位相对较富。锡石-硫化物型矿体受大理岩内的层间滑脱构造控制,富锡,而铍、钨相对较贫。伟晶岩型矿体矿化为铍为主,伴生铷等。钻孔深部验证发现夕卡岩型矿体、锡石-硫化物型矿体、锡石-石英脉型矿体深部延伸较稳定。通过岩浆与铍锡多金属成矿作用的关系的研究,提出了祥林矿区两期次铍锡钨多金属矿成矿作用,分别与弱定向二云母花岗岩及白云母花岗岩两期次淡色花岗岩浆活动密切相关。在矿体特征研究和矿床类型总结的基础上,明确了下一步的找矿标志和方向。锡石-硫化物型铍锡多金属矿和锡石-石英脉型铍锡多金属矿铍、锡、钨品位相对较富,为今后主攻的矿床类型。

关键词: 铍锡多金属矿, 地质特征, 找矿方向, 错那洞穹隆, 西藏

Abstract:

The Cuonadong gneiss dome, a newly discovered dome in the North Himalaya Gneiss Domes (NHGD) belt, is composed of three parts: core, mantle, and outer layer. They are composed of Cambrian granitic gneiss, Early Paleozoic mica schist and skarn marble, and metamorphic sedimentary rocks, respectively, and leucogranites and scores of pegmatite veins intrude into the core of the Cuonadong gneiss dome at a later stage. The Xianglin Be-Sn polymetallic ore deposit is located in the northern Cuonadong gneiss dome. A number of north-south and east-north extensional faults are developed in the mining area. The Be-Sn polymetallic orebodies were newly discovered through systematic surface exploration engineering in the mantle layer around the core of the dome and fault fracture zones. The anatomy of a typical mining area in the northern Cuonadong dome shows four types of ore bodies: skarn, cassiterite-quartz vein, cassiterite-sulfide, and granite pegmatite. Skarn type ore bodies occur in skarn marble in the mantle; mineralized is dominated by Sn, Be and W; Sn ore grade is relatively low. Cassite-quartz vein type ore bodies are controlled by NE extensional fracture; mineralization is dominated by Sn, Be and W; ore grades are relatively high. Cassite-sulfide orebodies are controlled by the interlayer slip structure in marble; Sn ore grade is high but Be and W ore grades are low. Mineralization in pegmatite is mainly Be, accompanied by Rb. Verified at great borehole depth, we found the deep extension of all types of ore bodies except pegmatite is relatively stable. Based on the study of the relationship between magma and Be-Sn polymetallic mineralization, we reveal that there are two stages of mineralization in the Xianglin mining area, and the mineralization is closely related to the weakly oriented two-mica granite and muscovite granite. Based on orebody characterization we developed a ore prospecting strategy. The main targets in future ore exploration will be cassite-sulfide and cassite-quartz vein type ores as they are relatively rich in Be, Sn and W.

Key words: Be-Sn polymetallic ore, geological characteristics, prospecting direction, Cuonadong, Tibet

中图分类号:

夏祥标, 李光明, 张林奎, 张志, 曹华文, 梁维. 西藏错那洞穹隆祥林铍锡多金属矿地质特征及找矿方向[J]. 地学前缘, 2022, 29(1): 93-106.

XIA Xiangbiao, LI Guangming, ZHANG Linkui, ZHANG Zhi, CAO Huawen, LIANG Wei. Geological characteristics of and prospecting strategy for the Xianglin Be-Sn polymetallic ore deposit in the Cuonadong gneiss dome in southern Tibet[J]. Earth Science Frontiers, 2022, 29(1): 93-106.

图/表 9

图1 北喜马拉雅片麻岩穹隆分布图 (据文献[14]修改)

Fig.1 Simplified geological map of the North Himalayan gneiss dome belt. Modified after [14].

图2 错那洞穹隆地质简图 (据文献[28]修改)

Fig.2 Simplified geological map of the Cuonadong gneiss dome. Modified after [28].

图3 祥林矿区地质简图

Fig.3 Simplified geological map of Xianglin mining district

图4 夕卡岩型矿体矿化特征 a—磁黄铁矿夕卡岩矿石;b—磁黄铁矿夕卡岩矿石中白钨矿的天蓝色荧光,白钨矿呈稠密浸染状分布;c—透辉石石榴子石夕卡岩矿石;d—透辉石石榴子石夕卡岩矿石中白钨矿的天蓝色荧光,白钨矿呈斑点状分布;e—石榴子石透辉石夕卡岩矿石;f—石榴子石透辉石夕卡岩矿石中白钨矿的天蓝色荧光,白钨矿呈稀疏斑点状分布;g—绿帘石符山石夕卡岩矿石中白钨矿的天蓝色荧光,白钨矿呈稀疏浸染状分布;h—绿帘石绿泥石夕卡岩矿石中白钨矿的天蓝色荧光,白钨矿呈星点状零星分布;i—夕卡岩矿石中锡石和石英共生,锡石具有结晶环带(正交偏光);j—显微镜下夕卡岩内的含铍矿物:硅铍石和羟硅铍石(BSD图像);k—夕卡岩矿石中白钨矿与石英共生(反射光);l—夕卡岩型矿体的野外露头,夕卡岩与弱定向二云母花岗岩直接接触。Po—磁黄铁矿;Grt—石榴子石;Di—透辉石;Sh—白钨矿;Ves—符山石;Chl—绿泥石;Qz—石英;Cst—锡石;Be—硅铍石;Ber—羟硅铍石;Ep—绿帘石;Tri—透闪石;sk—夕卡岩;γ1—弱定向二云母花岗岩;sch—黑云母石英片岩。

Fig.4 Mineralization characteristics of skarn type orebody

图5 锡石-石英脉型矿体矿化特征 a—锡石-石英脉型矿体野外宏观露头;b—伟晶岩内发育陡倾的电气石细脉、锡石细脉;c—伟晶岩内的锡石-石英脉:锡石、石英、白云母和萤石共生;d—云英岩化伟晶岩内的锡石-石英脉;e—锡石-石英脉型矿石中锡石、石英和白云母共生;f—云英岩化伟晶岩中的锡石颗粒及周边的孔雀石化,以及伟晶岩中的无色透明柱状绿柱石集合体;g—伟晶岩中的绿柱石和锡石共生;h—萤石脉野外露头;i—萤石中的白钨矿。Tur—电气石;Cst—锡石;Qz—石英;Ms—白云母;Fl—萤石;ρ—伟晶岩;Mal—孔雀石;Ber—绿柱石;γ—二云母花岗岩;Sh—白钨矿。

Fig.5 Mineralization characteristics of cassiterite-quartz vein type orebody

图6 锡石-硫化物型矿体矿化特征 a—锡石硫化物脉沿大理岩与伟晶岩脉的接触带产出;b—厚大的似层状锡石硫化物矿体内的伟晶岩透镜体;c—大理岩内条带状锡石硫化物脉;d—锡石硫化物脉中的锡石、黄铁矿、方解石、石英共生;e—块状锡石石英型矿石;f—锡石硫化物矿石中的黄铜矿和黄铁矿(光片,单偏光);g—锡石硫化物矿石中的黄铜矿、毒砂和白铁矿(光片,单偏光);h—锡石硫化物矿石中的黄铜矿、黄铁矿和褐铁矿(光片,单偏光);i—锡石硫化物矿石中的黄铜矿、黄铁矿和辉锑矿(光片,单偏光)。mb—大理岩;ρ—伟晶岩;Cst—锡石;Qz—石英;Cal—方解石;Py—黄铁矿;Ccp—黄铜矿;Apy—毒砂;Mrg—白铁矿;Lm—褐铁矿;Sti—辉锑矿。

Fig.6 Mineralization characteristics of cassiterite-sulfide orebody

图7 伟晶岩型矿体矿化特征 a—含绿柱石的伟晶岩脉顺黑云母石英片岩的片理面侵入;b—含绿柱石的伟晶岩脉切穿大理岩片理面;c—伟晶岩透镜体顺大理岩片理侵位后,经历了成穹过程的变形,在大理岩内拉伸呈透镜状;d—伟晶岩脉中的绿柱石断面呈六边形;e—伟晶岩脉中自形的绿柱石与石英、白云母共生;f—伟晶岩脉中的绿柱石晶体呈六方柱形。ρ—伟晶岩;sch—黑云母石英片岩;mb—大理岩;Ber—绿柱石;Qz—石英。

Fig.7 Mineralization characteristics of pegmatite orebody

表1 钻孔ZK502见矿情况一览表

Table 1 Basic information for ores from drill hole ZK502

矿体编号	孔深/m		矿体厚度/m	平均品位w_B/%
矿体编号	起	止	矿体厚度/m	BeO	WO₃	Sn
Z2	245.78	248.98	2.69	0.025	0.010	0.93
Z1-1	299.72	301.27	1.47	0.013	0.08	0.017
ρ1	313.37	316.42	2.90	0.096	0.001	0.006
Z1-1	330.02	336.67	4.80	0.066	0.16	0.12
Z1-1	347.66	352.17	4.29	0.077	0.13	0.09
ρ2	355.47	356.72	1.19	0.14	0.002	0.003
Z2	382.10	384.77	2.67	0.04	0.14	0.38
Z2	394.07	398.37	4.30	0.072	0.10	0.063
Z6	435.66	446.21	7.50	0.006	0.38	0.12
ρ3	530.52	532.27	1.75	0.051	0.001	0.007
ρ4	560.67	562.35	1.68	0.086	0.001	0.003

图8 祥林矿区5号勘探线剖面示意图

Fig.8 Cross-section along the No. 5 exploration line in Xianglin mining district

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