Yiyuan jade deposit, Luanchuan County, Luoyang, Henan, Chinai

Regional Level Types
Yiyuan jade deposit	Deposit
Luanchuan County	County
Luoyang	Prefecture-level City
Henan	Province
China	Country

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The Yiyuan jade is predominantly a serpentine−bearing marble formed by Neoproterozoic gabbro emplacement and subsequent low−temperature alteration. The deposit is hosted within the Meiyaogou Formation of the Luanchuan Group, which consists predominantly of dolomitic marble intercalated with thin layers of argillaceous limestone and calcareous mudstone, indicating deposition in a shallow marine carbonate platform environment. The Yiyuan jade ore bodies occur as stratiform or lenticular units within the dolomitic marble, generally striking WNW to NW and dipping 25−35° NE. They range in length from tens of meters to over 50 m and in thickness from 2 to 14 m. Spatially, the mineralization shows a clear association with contact zones between dolomitic marble and metamorphosed gabbroic dykes Green jade exhibits a massive structure and is primarily composed of epidote and actinolite. Epidote is approximately 200 μm in size and shows pale yellowish−green to light green pleochroism under plane−polarized light. Actinolite appears in irregular shapes and is distributed between epidote grains, with sizes ranging from 20 to 100 μm. White jade displays a massive structure dominated by calcite and dolomite. Calcite exhibits an anhedral granular texture with grain sizes between 0.2 and 1.2 mm. Dolomite grains are similar in size to calcite but often appear blurred on the surface due to weathering. Bluish−white jade shows a massive structure and is dominated by calcite and dolomite minerals, with some occurrences of antigorite, clinochlore, or forsterite. Calcite is anhedral, granular, and 50−100 μm in size. Dolomite is often surrounded by calcite and also appears anhedral and granular, with comparable grain sizes. Bluish−black jade has a more complex composition, with less calcite and dolomite but more antigorite. Some samples contain clinochlore and chamosite, and the proportions of albite, quartz, and biotite are higher. In antigorite−dominant samples, antigorite appears as elongated columnar or fibrous crystals, ranging from 0.3 to 1.2 mm in length. In chamosite−dominant samples, chamosite occurs as platy crystals with a granular texture, approximately 100−300 μm in length, displaying light green to green pleochroism.

Yiyuan jade occurs between two major fault zones, the Luonan–Luanchuan–Fangcheng fault zone (LLFF) to the south and Machaoying fault zone (MF) to the north, and on the northern flank of the Sanchuan–Miaozi syncline. From north to south, the exposed strata mainly include the Archean Taihua Group, the Paleoproterozoic Xiong’er Group and Guandaokou Group, the Neoproterozoic Luanchuan Group, and the Paleozoic Taowan and Kuanping Groups. The Meiyaogou Formation is a clastic-carbonate sedimentary sequence. It can be subdivided into three sections based on its assemblage and sedimentary architecture (Figure 2b). The lower section consists mainly of biotite-quartz marble, quartz marble, and dolomitic marble, intercalated with calcareous schist. The middle section comprises sericite–plagioclase schist and two-mica schist, with lenses of dolomitic marble. The upper section is dominated by dolomitic marble and biotite quartz marble, interbedded with thin layers of sericite plagioclase schist and two-mica schist. The upper section hosts Yiyuan jade and can be further subdivided into three parts from bottom to top: (i) quartzite with intercalated two-mica schist; (ii) thick-bedded dolomitic marble; and (iii) dolomitic marble and stromatolite marble, with minor quartz sericite schist and coal-stone beds.
In the Yuegou, Sanhecun, and Zhuanggou areas, a total of eight Yiyuan jade ore bodies were discovered. They are mainly lenticular, banded, vein-shaped, or lamellar in form, trending NW–SE or nearly E–W. These jade bodies are primarily composed of serpentinized marble, tremolitized marble, tremolite jade, and serpentine jade. The jade body in the Sanhecun area occurs within marble and the contact zone between marble and metagabbro, with a length of approximately 50–70 m, a width of about 14–20 m, dipping NE at 65–73°. Based on detailed petrological and mineralogical characterization, three subtypes of Yiyuan jade are defined: tremolite jade (tremolite ≥ 90%), serpentine jade (serpentine ≥ 90%), and their transitional varieties. Genetically, the deposit is classified as a metamorphic–hydrothermal metasomatic type.

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17 valid minerals.

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