Discovery of strata-bound copper deposit in the Arqueros area, Northern Chile

DOI Web Site 20 References

Bibliographic Information

Other Title
  • チリ共和国アルケロス地区における層準規制型銅鉱床の発見
  • 現場担当者会議講演論文 チリ共和国アルケロス地区における層準規制型銅鉱床の発見
  • ゲンバ タントウシャ カイギ コウエン ロンブン チリ キョウワコク アルケロス チク ニ オケル ソウ ジュンキセイガタ ドウコウショウ ノ ハッケン

Search this article

Abstract

The Arqueros area comprising third party's mining concessions of approximately 50 km2, is situated in the Lower Cretaceous strata-bound copper (-silver) metallogenic belt in Northern Chile. This area had persisted unexplored for many years in spite of its geographical proximity to some operating copper mines and active exploration sites. Sojitz Corporation and Nittetsu Mining Co., Ltd., focusing on its potential of mineral deposit, jointly acquired their exploration rights in July and started exploring it in September, 2011. After two phases of activities, the companies have discovered concealed strata-bound copper (-silver) deposit hosted in a limestone member in the volcanic rock-dominated Lower Cretaceous Arqueros Formation.<br>In the first phase (September to December, 2011), surface geological and scout drilling surveys were conducted under the Overseas Geological Survey Program by Japan Oil, Gas and Metals National Corporation (JOGMEC). A great potential of copper ore deposit within the limestone member was revealed by the geological survey from a similarity of geology with the adjoining copper mine. And then a scout core drilling of 14 vertical holes (2,971.75 m) was performed in the prospective areas extracted by the geological survey. The two neighboring holes which are about 500 m away from each other, intersected mineralized intervals of 7.00 m @1.41% Cu, 23.8 g/t Ag and 10.90 m @0.81% Cu, 11.8 g/t Ag at a cut-off grade of 0.5% Cu, respectively, in the same limestone horizon.<br>In the second phase (April to June, 2012), additional 12 vertical core holes were arranged at 300 to 500 m spacing around the two holes over the area stretching 1.5 km from east to west and 2 km from north to south, and were drilled (totaling 3,191.75 m) to test lateral continuity of those ore intersections. Eight holes of them successfully confirmed copper mineralization of 5.5-20 m thick grading 0.8-1.6% Cu and 9-37 g/t Ag in that particular limestone horizon, which forms a continuous stratiform ore body spreading over an area of at least 1 km x 1.5 km. Mineralization consists of finely-disseminated chalcocite, bornite and chalcopyrite in an inter-clast matrix, dissolved calcareous fragments, and calcite veins and veinlets. Since the outer limit of mineralization has not yet been confirmed, this stratiform ore deposit can be extended toward the outside depending on the results of future exploration works.<br>At the present stage, estimating mineral resources is a task of immediate importance. For this purpose, a grid drilling at approximately 200 m spacing is required over the second phase-exploration area. A scout drilling in the surrounding area also is highly recommended for testing further extension of the discovered ore deposit.

Journal

  • Shigen-Chishitsu

    Shigen-Chishitsu 63 (2), 69-80, 2013

    The Society of Resource Geology

References(20)*help

See more

Keywords

Details 詳細情報について

Report a problem

Back to top