Summary:
A total of 18 gold mineralization domains were defined, where two sub-zones were named as NE zone and SW zone, covering NE open pit and SW open pit, respectively. NE zone accounts for 78% of the total mineral resources of the CSH gold deposit, where SW zone occupies 22%only.
Gold mineralization domain N1: The largest size of gold domain at the cross section of explorationline8,800 to 11,100 was defined in the CSH deposit area, with an irregular tabular shape, and controlled by bedding-like shear structures. The mineralised domain is totally hosted in the second Member of Bilute Formation, Mesoproterozoic Bayan Obo Group, with most parts outcropped on the surface. It strikes NE55°to 65° overall, plunging NW at a dip of 70 – 85°. As shown in Figure 7-5, a total of 645 diamond drill holes on a grid of 50–100 m (strike) by 50–100 m (plunge) have delineated the domain for a length of 2,346malong the strike and a plunge extension of 1,100 – 1,540 m, with a horizontal thickness of 70 – 400m. The elevation of the domain ranges from 1,677 m to 230 m ASL. The domain N1, accounting for about 76.5%ofthe total mineral resources of the CSH Gold Deposit, is dominated by gold mineralization grading0.57g/t Au.
Gold mineralization domain W1: The second largest size of gold domain at the cross section of exploration line 6,700 to 9,100 was defined in the CSH gold deposit area, with a strata-bound shape, and controlled by bedding shear structures. The mineralised domain is totally hosted in the second Member of Bilute Formation, Mesoproterozoic Bayan Obo Group, with most parts outcropped on the surface. One post-mineralization fault offset the mineralized zone at the exploration line 7,300 to 7,500. It strikes NE65–70°overall, plunging NW with a dip of 85 – 90°. A total of 277 diamond drill holes on a grid of 25–100 m(strike)by 25–100 m (plunge) have delineated the domain for a length of 2,400 m along the strike and a plunge extension of 610–750 m, with a horizontal thickness of 90–116 m. The elevation of the domain ranges from1,655 m to 905 m ASL. The domain W1, accounting for about 21.6% of the total mineral resources of the CSH Gold Deposit, and is dominated by gold mineralization grading 0.56 g/t Au.
The metallic minerals are mainly composed of pyrrhotite and pyrite with minor chalcopyrite, sphalerite, galena, arsenopyrite, native gold, and electrum, etc., and gangue minerals consist of quartz, mica group, and feldspar, with minor calcite, diopside, tremolite, and apatite etc. Statistic data indicate that about 74% golds occur in interstitial among sulfides and gangue minerals, or hosted in fissures of various minerals, implying that most gold is easy to be recovered.
The mineralization texture recognised match those of the original rocks for most mineralized materials, with sparsely disseminated sulfides, and local stock work quartz veinlet or pyrite veinlet. Statistic data exhibit that more than 50% sulfides size less than 0.074 mm (200 mesh). Gold minerals include native gold and electrum, appearing in un regular shape with 8.42% more than 200 mesh. Gold minerals usually occur along with various sulfides, and the high-grade gold mineralization is always associated with stock work quartz veinlets and pyrite veinlets.
The characteristics of the gold mineralization at the CSH deposit are summarized as follows:
• The CSH gold deposit is a low-grade but large size deposit. Tectonically, the CSH gold deposit is located in the northern edge of North China platform, which was uplifted to continental environment after the Hercynian orogeny in the Permian Period and characterised by intensely developed magmatic intrusions emplaced during the Hercynian orogeny. The tectonic unit is different from the geological setting of Muruntau or Sawaya’erdun gold deposits located at the Tianshan-Mongolia Hercynian fold belt in China;
• Gold mineralization of the CSH deposit is hosted in low-grade metamorphic rocks of Mesoproterozoic Bayan Obo Group, controlled by a brittle-ductile shear structure, which is assumed to have been formed in Hercynian orogeny. Various dykes such as lamprophyre, diabase, diorite, aplite and pegmatite, etc. and quartz vein were developed along the brittle-ductile shear structure. Gold mineralization was formed at the late stage after quartz vein and various dykes, which was in ten so-shear state during mineralization process. The alter at ion of gold mineralization is very weak in general, but coarse gold mineralization is always associated with stock work quartz and pyrite veinlets; and
• Data of microscopic study and various tests indicate that mineralization is dominated by native gold and electrum with minor visible gold, but low-grade silver (less than 2 g/t), less fine-grained pyrite (about 0.26%). Both oxidized and primary mineralized materials are easy for heap leaching.
It is believed that the CSH gold deposit is of an orogenic style mineralization, hosted in Mesoproterozoiclow-grade metamorphic horizon and characterised by low-grade gold mineralization but large size.