Controls on Ore Shoot Locations and Geometries at the Stawell Gold Mine, Southeastern Australia: Contributions of the Volcanosedimentary, Alteration, and Structural Architecture

• DOI: 10.2113/gsecongeo.103.5.1029
• Publication Date: 2008-12-03T14:55:23Z
• Authors: R. J. Squire; J. A. Robinson; T. J. Rawling; C. J.L. Wilson
• Keywords: 15. Life on land; 01 natural sciences; 0105 earth and related environmental sciences

The ability to effectively target ore shoots requires a clear understanding of the numerous parameters that control their formation. However, identification nature and timing these is difficult, particularly in polydeformed deposits with complex stratigraphic hydrothermal histories. For example, at Stawell gold mine’s Magdala southeastern Australia are hosted by rocks experienced least three ductile two brittle deformation events 70 m.y. prior principal mineralization event, have close spatial relationship strongly chlorite ± stilpnomelane–altered sedimentary units near apex >5-m-thick reentrant basalt lobes. Whereas located only on southwestern flank 1-km-thick basalt, about 15 km along strike Wildwood prospect predominantly restricted northeastern basalt. Here, important issue controls shoot formation distribution addressed presenting results multidisciplinary review characteristics architecture volcanic facies, alteration assemblages, variations intensity vergence relationships cleavages associated deformation. This investigation, undertaken both regional scale, shows structures hosting formed during preferential localized reactivation preexisting faults following rotation stress field. Preexisting structures, such as Central Lode fault, host many were initially generated east-northeast–west-southwest compression ca. 510 488 Ma. geometries also influenced irregular paleotopography lobes, which represent flows pillow massive separated interflow units. Coincident this deformation, locally intense stilpnomelane indurated mud-rich between flow-lobes Lode-type structures. Those thick, present Stawell, but top Wildwood. switch east-west 440 Ma caused failure focusing mineralized fluids northwest-plunging portions A second, subordinate mineralizing event 425 420 utilized same under different regime. During events, high-grade zones high fluid flow defined architecture.