Irving Resources has received high-grade assays from surface samples recently collected at the Omui Gold-Silver Project in Hokkaido, Japan. Reconnaissance sampling focused on areas around the historic Omui and Hokuryu mines where high-grade epithermal gold-silver veins were exploited prior to World War II.
Irving staff with assistance from personnel from Mitsui Mineral Development Engineering Co Ltd (MINDECO) collected 130 rock chip samples.
At the Honpi (Main Vein) occurrence, rock chip samples collected from float boulders of vein material returned exceptional assays including 480 g/t gold and 9660 g/t silver; 143.5 g/t gold and 2090 g/t silver; 67.6 g/t gold and 1060 g/t silver; 55.6 g/t gold and 290 g/t silver; and 48.2 g/t gold and 1030 g/t silver. A further 14 samples assayed greater than 10 g/t gold and 13 samples assayed greater than 200 g/t silver.
Many high grade samples originate from areas north of the Main Vein. This is an E-W trending epithermal quartz vein that was exploited during the 1920s by a 70 metre deep shaft and four working levels including several stopes, now collapsed to surface. Approximately 0.4 tonnes of gold and 9 tonnes of silver were mined at Omui during that time.
Irving believes the boulders it sampled originate from sub-cropping veins that were neither recognised nor exploited during that early period of mining. Further work, including drilling, is needed to evaluate this possibility.
At Nanko, approximately 1km south of Honpi, Irving collected float and sub-crop samples of siliceous material thought to be sinter, a hard material deposited from hydrothermal fluids in shallow hot spring pools. Sinter typically contains low level gold whereas fractures, or feeders, below hot springs can host high grade gold, deposited there by boiling fluids.
Most samples of sinter from Nanko are anomalous in gold up to 1 g/t. Two samples of breccia contain notable high grades, 29.6 g/t gold and 73.8 g/t silver, and 21.2 g/t gold and 154 g/t silver, respectively. These high-grade samples appear to originate from sub-cropping feeder structures that may indicate the presence of high grades at depth. Further work, including drilling, is needed to test this potential.
Four select samples of vein material collected from a mine dump adjacent to the uppermost workings of the Hokuryu mine returned 58.9 g/t gold and 495 g/t silver; 51.4 g/t gold and 637 g/t silver; 37.0 g/t gold and 378 g/t silver; and 22.8 g/t gold and 321 g/t silver. Another two select samples of vein material from the main Hokuryu mine dump assayed 31.4 g/t gold and 201 g/t silver, and 11.4 g/t gold and 38.2 g/t silver. One sample of silicified and pyritised rhyolite wallrock taken from the main dump assayed 2.2 g/t gold and 245 g/t silver.
Hokuryu mine produced approximately 2.8 tonnes of gold and 11.5 tonnes of silver prior to 1943 when it was abruptly closed due to the Gold Mine Closure Act near the end of World War II.
Irving thinks exploration potential around Hokuryu is very good, particularly along a major NE-trending graben-bounding fault that extends about 12 km to the coast. Irving has recently discovered new, extensive sinter deposits along this structure. Such sinter indicates this fault was a focus for hydrothermal activity.