Model: typical VMS-type Pb-Zn deposit. The strata exposed in the study area are mainly the Ordovician Qimantag Group (OQ) and Quaternary (Q). The Qimantag Group, the main stratigraphic unit, forms a NW-trending belt and belongs to a marine volcanic exhalative-sedimentary sequence. It can be subdivided, from bottom to top, into the Volcanic Formation (OQ1), Clastic Formation (OQ2), and Carbonate Formation (OQ3). The Volcanic Formation consists of interbedded basalt, basaltic andesite, and dacite, locally intercalated with banded siliceous rocks. It commonly exhibits hydrothermal alterations such as sericitization, chloritization, and silicification, and is the main ore-bearing stratum in the study area. The Clastic Formation conformably overlies the Volcanic Formation and consists of lithic arkose, sandy slate, and siltstone. The Carbonate Formation consists of interbedded limestone and marble, exhibiting a parallel unconformity with the underlying Clastic Formation. Tectonic activity in the area is dominated by NW-trending regional faults, which are post-ore structures controlling the distribution of strata and intrusions and have partially disrupted the orebodies. Currently, five zinc orebodies (numbered M2-M6) have been delineated at the Donggou deposit, all hosted within the Volcanic Formation of the Qimantag Group. Except for local surface exposures of the M4 orebody, the others are blind orebodies. The orebodies are generally stratiform, lenticular, or lens-shaped, with lengths ranging from 200 to 800 m, thicknesses from 1.46 to 12.68 m, burial depths from 330 to 810 m, and average grades of Zn 3.10%, Cu 0.22%, Pb 0.23%, Au 0.41 g/t, and Ag 13.69 g/t. The M4 orebody is the main orebody of the deposit, with a length of 400 m, a thickness of 2.95 m, a maximum burial depth of 810 m, and average grades of Zn 5.96%, Pb 0.76%, Cu 0.52%, Au 0.41 g/t, and Ag 25.71 g/t. Notably, the M4 orebody of the Donggou deposit preserves a complete and continuous volcanic exhalative-sedimentary sequence typical of VMS deposits. The orebodies are stratiform and continuously developed, with no obvious post‑ore crosscutting, replacement, or overprinting structures.

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References