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Jinfeng, Lannigou, Yata

Guizhou, China

Main commodities: Au Hg
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The Jinfeng gold deposit (also known as Lannigou) is located near the town of Lannigou in south-western Guizhou Province in southern China, approximately 240 km south west of the provincial capital Guiyang (#Location: 25° 8' 50"N, 105° 52' 22"E).

When discovered, Jinfeng was the largest of the known "Carlin type" gold deposits in the Golden Triangle area of southern China. Mercury and arsenic mining in the vicinity of the deposit had been ongoing for more than 100 years before a regional geochemical survey in the 1980's delineated a series of gold anomalies in the area, one of which corresponded to the arsenic working over what is now the main Jinfeng deposit.

The regional geology of Jinfeng district comprises Permian to Triassic sedimentary rocks of the Youjian Basin, which are concentrated along the western margin of the Proterozoic Yangtze craton. The stratigraphic succession in the Youjian Basin commences with Cambrian to Carboniferous massive limestones, overlain by Permian shelf limestones. The Palaeozoic carbonates are followed by Lower Triassic platy limestones, in turn overlain by Middle Triassic alternating mud and sandstones with classic turbidite sequences above. Most of the gold deposits in the region are found in clastic rocks within the latter sequence, and are spatially associated with faults zones and broad antiformal culminations (Juras et al., 2011).

Stratigraphic units in the Jinfeng mine district have been divided into two distinct sequences: i). a lower dominantly carbonate bearing sequence and ii). an upper mudstone and sandstone lithology dominant sequence. The upper sequence is well exposed in the Jinfeng open pit, and is host to the gold mineralisation of the deposit. The contact between upper and lower sequences is a regional unconformity, but near Jinfeng it is commonly faulted (Juras et al., 2011).

Jinfeng is situated on the eastern margin of a 25 x 12 km domal structure with a core of Carboniferous and Permian reef, bioclastic and massive limestones, unconformably overlain and structurally flanked by early to mid Triassic turbidites, mainly bedded, calcareous sandstones, siltstones, wackes, fossiliferous and carbonaceous shales, and minor limestones. The Triassic sediments are believed to have been deposited on the continental slope margin, bounded by abyssal marine facies to the south-east and platformal sediments to the north-west.

The main ore controls are broad fault zones that cut the initial phase of folds but were reactivated during the later fold and thrust event. Gold mineralization is superimposed on this complex geology with higher grades developing at fault intersections and within favourable lithologic units. It occurs along steeply dipping NW and SW oriented faults, near the crests of anticlines and in all lithologies, although the most significant is in turbidites, particularly within 1 km of the Permian contact where calcareous units predominate. It also occurs in a important stratabound zone within calcareous arenites.

Three significant zones of mineralisation have been outlined, specifically Hongchanggou (HGC), Rongban and Lintan. At HGC, gold is concentrated at the junction of two faults cutting an open NW trending anticline. The bulk of the ore is within the WNW striking, steeply NE dipping of the two faults, although the other, a SW striking, SE dipping structure offsets the first and hosts the Rongan zone a few hundred metres to the north. The country rocks are intensely disrupted by the faults, with the more competent arenites being broken into blocks within milled shale and clay gouge zones over widths of up to 30 m which have sharp contacts with the drag folded enclosing lithologies. Ore shoots plunge steeply east, parallel to the intersection trace of the two faults. These shoots are bifurcating and lenticular, with complex internal geology, rapid pinching and swelling, and numerous splays. Their widths average 11 m, but are locally up to 30 m thick. Higher grade blocks (>8 g/t Au) are in the thicker parts of the shoot and where they cut coarser grained calcareous arenites. Where the country rocks are finer, grades are generally lower.

Stratabound mineralisation has been intersected over widths of 50 m at depths of 500 m below the surface within the quartz±carbonate (dolomite/ankerite) matrix of a calcareous arenite.

Gold mineralization is typically associated with highly carbonaceous gouge material or cataclastic breccia, fault gouge seams and styolitic shear veins, silicified wall rock, breccias and veins with illite-dolomite alteration, and quartz-dolomite-orpiment veins and stockwork. Gold occurs as sub-micron gold within the lattice of finely disseminated arsenian pyrite and pyrite (the former often occurring as arsenical rims to earlier pyrite). These sulphides are overprinted by coarser, gold poor, disseminated, stockwork and crackle veined orpiment, realgar, cinnabar and stibnite. Alteration includes silicification, dolomitisation, argillisation and carbonation as well as sulphidation associated with the mineralisation. Acid solutions responsible for this alteration and mineralisation have resulted in the dissolution of the carbonatic matrix of calcareous arenites, thus increasing the porosity with the partial replacement of calcite by dolomite.

Resources announced in June 2004 amounted to 20.9 Mt @ 5.1 g/t Au for 107 tonnes (3.454 Moz) of contained gold.

Mineral resources announced in June 2008 amounted to 35.9 Mt @ 4.7 g/t Au for 165 tonnes (5.3 Moz) of contained gold, of which
            30.5 Mt @ 4.7 g/t Au were measured + indicated resources (Sino Gold, 2008).

Remaining ore reserves and mineral resources at 31 December, 2015 (Eldorado Gold, 2016) were:
    Proved + probable reserve - 15.127 Mt @ 3.83 g/t Au;
    Measured + indicated resource - 19.916 Mt @ 3.91 g/t Au;
    Inferred resource - 7.818 Mt @ 3.83 g/t Au (Mineral resources are inclusive of ore reserves).     Contained gold in total resource = 79.1 t.

The Jinfeng project commenced mining in late 2005 and was 82% owned by Sino Gold Limited via a joint venture with Chinese partners. In 2009, Eldorado Gold Corporation purchased Sino Gold Limited. In 2016, Eldorado Gold sold its 82% holding in the Jinfeng JV to a subsidiary of China National Gold Group Corporation.

The Yata gold deposit is located approximately 15 km to the SW of Lannigou and has a resource of around 10 t Au at grades of 3 to 5 g/t Au.

For more detail on Jinfeng, see: Juras, S., Miller, R., Skayman, P. and Pitcher, N., 2011 - Technical Report for the Jinfeng Gold Mine, China; an NI 43-101 Technical Report, prepared for Eldorado Gold Corporation, 142p."

The most recent source geological information used to prepare this summary was dated: 2011.     Record last updated: 9/9/2016
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd.   Unauthorised copying, reproduction, storage or dissemination prohibited.


Jinfeng

  References & Additional Information
 References to this deposit in the PGC Literature Collection:
Su Wenchao, Heinrich CA, Pettke T, Zhang Xingchun, Hu Ruizhong and Xia Bin,  2009 - Sediment-Hosted Gold Deposits in Guizhou, China: Products of Wall-Rock Sulfidation by Deep Crustal Fluids : in    Econ. Geol.   v104 pp 73-93
Wilde A R  2003 - The Golden Triangle of southeast China: Another Carlin Trend ?: in    SEG Newsletter, Soc. Econ. Geol., Denver   No. 55, Oct 2003 pp 1, 9-12


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