Chaihulanzi Mine, Songshan District, Chifeng City (Ulanhad League; Chifeng Prefecture), Inner Mongolia, Chinai

Regional Level Types
Chaihulanzi Mine	Mine
Songshan District	District
Chifeng City (Ulanhad League; Chifeng Prefecture)	Prefecture-level City
Inner Mongolia	Autonomous Region
China	Country

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Quartz vein and altered rock type gold deposit, hosted in Archean marble and graphite-bearing schist. Gold mineralization is closely related to a Mesozoic augite diorite stock. The rocks contain abundant mafic xenoliths.

The Chaihulanzi deposit is a large lode-type gold deposit (∼27 t Au at 3.6 g/t) situated on the northern margin of the North China Craton (NCC). The strata exposed in the ore district mainly consist of the Neoarchean–Paleoproterozoic Jianping Group, which comprises Archean mafic gneiss, granitic gneiss, graphite-bearing mica schist, and migmatite, with Paleoproterozoic mantle-derived carbonatites intruding into these rocks underground. Eighteen gold orebodies were delineated, among which I–5 was the main orebody. The I–5 orebody strikes NW and dips ∼ 70° SW, with a length of 1500 m and slope depth of 700 m. Mineralization can be classified into two types: quartz-vein-type mineralization and altered-rock-type mineralization. The altered-rock-type mineralization can be further subdivided into two subtypes: altered-schist-type mineralization and altered-diorite-type mineralization. Reserves: 27 t @ 3.6 g/t Au.

The Chaihulanzi gold deposit, hosted by the Archean Jianping Group, represents the oldest known orogenic gold deposit at the northern margin of the North China Craton (NCC). The orebodies of the Chaihulanzi gold deposit are controlled by different structural (transtensional and transpressional) systems and different wall rocks (graphite-bearing schist, gneiss, diorite porphyry). Orebodies controlled by transpressional faults are characterized by narrow (<5 m) and continuous lodes that extend farther in length and depth, with relatively smooth fracture surfaces and continuity. These orebodies are tabular in shape, with stable attitudes. The largest and main mining orebody among them has a total length of approximately 725 m, a maximum vertical extension of nearly 500 m, and an average thickness of 1.45 m, with grades ranging from 0.1 to 39.84 g/t. It trends NW and dips SE at angles of 50–80°. In contrast, orebodies controlled by the transtensional faults are characterized by an overall shallow mineralization position, shorter vein lengths, and relatively rough fracture surfaces. These lodes are typically wide (>5–10 m) and discontinuous, often containing a significant amount of dilational host rock breccia, and are separated from shear zones by various types of barren host rocks. In addition, these orebodies are mostly irregular lens-shaped, with localized ore nodules and abrupt thickness variations. Multiple veins have lengths ranging from 110 to 230 m, with maximum vertical extension of about 250 m and thickness variation from 1.1 to 9.9 m, and grades between 0.13 and 17.4 g/t. According to the orebody numbering in the mining area, orebodies No. I-1, I-2, I-3, I-4, I-7, I-8, and No. II were controlled by transtensional faults, whereas orebodies I-5 and I-9 were controlled by transpressional faults.

The Chaihulanzi gold deposit hosts 18 orebodies controlled by dilatant fractures. Three types of mineralization have been identified based on their style, host lithology, and associated wall-rock alteration: altered porphyrite (V1), altered mica schist (V2), and auriferous quartz veins (V3).
The V3-type mineralization represents the most economically significant and spatially extensive ore type in the deposit, hosting the thickest and highest-grade orebodies. It occurs predominantly as stratabound quartz veins and auriferous saddle reefs. These orebodies maintain sharp, discordant contacts with the marble and graphitic mica schist of the Dayingzi Formation. Representative orebodies (e.g., I-4, I-8, II-2) are substantial, with strike lengths of 70–275 m, thicknesses of 4–9 m, and down-dip extents of 110–800 m. Gold grades within these orebodies range from 3.7 to 28.4 g/t.

Commodity List

This is a list of exploitable or exploited mineral commodities recorded at this locality.

Mineral List

23 valid minerals.

Rock Types Recorded