Springfield basin, Cradock, Flinders Ranges Council, South Australia, Australiai

Regional Level Types
Springfield basin	Basin
Cradock	Town
Flinders Ranges Council	Local Government Area
South Australia	State
Australia	Country

Conglomerates

128 diamonds and fragments were recovered in the mid-1980s from Permian basal conglomerate. In 1998, an additional 56 diamonds were recovered from renewed exploration trenching, the largest being 3.5 mm and weighing 0.34 ct. Fresh indicator minerals, particularly garnet with a kelyphytic rind, suggested that the kimberlite source was relatively close to the basin. Site is that of exposed conglomerate of the basal conglomerate, Conglomerate unit A located at the SE-extent of the basin , and from which diamonds were recovered from a ~1m thick cobble unit as exposed in costeans. Surface mapping of the basal conglomerate or Conglomerate Unit A suggested the unit represents material deposited in river channels. Flow direction as estimated from studies of clast orientation indicate flow for the very basal member was into the area from a south-westerly direction. Subsequent drilling of 6 diamond holes confirmed continuity and thickening of conglomeritic beds within this basal sequence including the persistence of basal conglomerates, including a possible correlative of the diamondiferous cobble unit with a thickness of 2.05m. A study of indicator minerals from the core indicated a freshness that suggests a primary source in close proximity, possibly within 2km of the basin edge. Suggested volume of basal unit from mapping and drilling was 1.82 million cubic metres (for thickness 1.66m), and for overlying conglomerate unit with thickness 6.3m = 6.95 million cubic metres.

Other Regions, Features and Areas containing this locality

References