Dalong Sn deposit, Zhenkang County, Lincang, Yunnan, Chinai

Regional Level Types
Dalong Sn deposit	Deposit
Zhenkang County	County
Lincang	Prefecture-level City
Yunnan	Province
China	Country

The deposit hosts 1,855 t Sn with an average grade of 0.4 %. Strata are mainly the Cambrian to Permian sedimentary layers, intercalated with Permian-Triassic basalt. The Upper Cambrian Baoshan Formation (Є3b), serving as the main Sn ore-hosting unit, is subdivided into five lithological members. (1) The first member (Є3b1) consists of banded limestone, intercalated with dolomitic limestone. (2) The second member (Є3b2) consists of silty clay slate and calcareous silty clay slate. The top and bottom parts have higher calcium content and exhibit transitional contacts with the adjacent members. (3) The third member (Є3b3) is composed of light gray and grayish-white medium to thick-bedded banded micritic limestone, intercalated with sandy and calcareous clay slate layers. (4) the fourth member (Є3b4) is gray, grayish-green, and locally purplish-red thin to medium-thick bedded sandy and sandy clay slate. The top and bottom parts exhibit relatively higher calcium content. (5) The fifth member (Є3b5) consists of bedded micritic limestone, intercalated with thin-bedded calcareous and silty clay slate. Members Є3b2, Є3b3, and Є3b4 constitute the primary ore-bearing unit.
he Dalong deposit comprises 11 tin ore bodies and several scattered tin-mineralized bodies. The ore bodies are controlled by both structure and stratigraphy, primarily occurring within the NE-trending fault system and their associated interlayer compressional fracture zones. Based on the host strata, three ore zones can be delineated: the Upper Ore Zone (Є3b4), the Middle Ore Zone (Є3b3), and the Lower Ore Zone (Є3b2). The area covered by mineralized bodies is approximately 2 km2. The ore bodies strike 240°–260°, dip NW at 20°–80° (consistent with wall rock attitudes), 40–430 m in length, 10–250 m in depth, and 0.5–10 m in thickness, with Sn grades varying between 0.21 % and 1.59 %. Among the ore bodies, V2, V3, V8, and V9 are the largest, accounting for 85 % of the total reserves. Three ore types are recognized at Dalong: (1) cassiterite-tourmaline-sulfide-quartz ore (main ore type; hosted in sulfide-quartz veins), (2) cassiterite-tourmaline-sulfide-sericite ore (hosted in wallrocks with intensive sericitization), and (3) oxidized limonite-cassiterite ore. Ores exhibit disseminated, veinlet, stockwork, or honeycomb morphologies.

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References