Summary:
Deposit Types
Gold mineralisation of the SJG (Songjiagou) Project is hosted within the pyritic-sericitic conglomerate of the Linsishan Formation from Laiyang Group of Cretaceous-age. Gold enrichment occurs as veins, as well as in disseminated and stockwork distributions. The SJG vein-type mineralisation could be appropriately described as mesothermal genesis. The disseminated and stockwork types of mineralisation have some aspects of epithermal mineralisation but are both spatially and genetically associated with the vein-type; as such it can be considered a variant of that type.
The SJG Project’s conglomerate type gold deposit is believed to be associated with mesothermal filling activities and followed by alterations and metasomatism.
Property geology
The SJG Project is situated in the eastern part of the Jiaobei Terrane and on the northeast margin of the Jiaolai Basin and is regarded as part of the Muping-Rushan gold belt.
Paleoproterozoic metamorphic rocks of the Jingshan Group are mainly distributed to the north of the SJG Project area near Tanjia village, and are comprised of biotite granulite, graphite-bearing gneiss, leucogranite, and marble. These strata generally dip southeast with angles varying from 15° to 50°.
Cretaceous-age rocks are predominately represented by the Linsishan Formation, part of the Laiyang Group and comprised of conglomerate and sandstone. The Linsishan Formation in the SJG Project area has an overall northeast strike and dips southeast with an angle of 20° to 40°. The formation is divisible into two conformably contacted sections according to the clast size. The first section of Linsishan Formation consists of relatively larger clasts with grain sizes of about 3 centimetres (‘‘cm’’) –20 cm and is predominately composed of monzonitic granite and quartz; marble, gneiss, schist and granulite are occasionally visible in this section. The second section is characterised by finer grained and rounded clasts made of sandstone and siltstone.
The gold mineralisation is mainly hosted within the conglomerate in first section of the Laiyang Group Linsishan Formation.
Mineralised zones
The SJG Project’s gold mineralised zones are concentrated within an area of approximately 1.0 km2 which is covered by the aggregate areas of Yantai Zhongjia’s currently valid mining licences. The defined mineralised zones are bounded within the Laiyang Group Linsishan Formation conglomerate without distinct boundaries, and a number of gold enriched bodies present as gold veins occurring within the lithological zone characterised by Linsishan Formation conglomerate.
The highest grades of gold mineralisation are confined to relatively narrow although vertically and horizontally persistent zones. Gold mineralisation is associated with sulphides. Mineralised rocks present in grained, in-filling, clastic, or brecciated textures.
Gold mineralisation is associated with sulphides that include electrum, pyrite, chalcopyrite, galena, sphalerite, and bornite. Gold is most abundantly associated with electrum and pyrite. The secondary metallic minerals include sphalerite, galena, chalcopyrite, magnetite, and limonite. The associated gangue minerals are represented by feldspar, quartz, muscovite, calcite, and clay minerals.
Sulphur (‘‘S’’) grades vary from 1.1% to 7.8% according to tests done on 13 samples by No. 3 Geological Institute, with an average grade of 3.7%. Silver (‘‘Ag’’) grades have been analysed within a range of 0.5 g/t and 8.5 g/t Ag. The harmful element arsenic (‘‘As’’) was found to occur with grades ranging from 0.0040% to 0.0302% As. The average grade of arsenic is about 0.0012% As. As the content of arsenic is far lower than the required standard of 0.5% in the content of the gold product as stipulated in the sales contract, SRK does not consider this could materially affect the saleability of the gold produced at the mines. Furthermore, in view of the graded of arsenic, SRK do not consider that it would be likely to adversely impact the environment.
Based on observation as well as on the phase analysis results, the types of gold mineralised zones present at the SJG Project include oxidised, mixed, and primary sulphide; primary sulphide or accounts for the largest proportion. The mineralised rocks present in grained, in-filling, clastic, or brecciated textures.