Geological characteristics of and prospecting strategy for the Xianglin Be-Sn polymetallic ore deposit in the Cuonadong gneiss dome in southern Tibet

doi:10.13745/j.esf.sf.2021.8.30

Abstract

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

CLC Number:

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.

Figures/Tables 9

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

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

Fig.3 Simplified geological map of Xianglin mining district

Fig.4 Mineralization characteristics of skarn type orebody

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

Fig.6 Mineralization characteristics of cassiterite-sulfide orebody

Fig.7 Mineralization characteristics of pegmatite orebody

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

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

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