Recent geological advances concerning the H.Y.C. and associated deposits,McArthur river,N.Y.

Recent mineral exploration in the McArthur River District, Northern Territory, has found new areas of base‐metal mineralization and has resulted in a reinterpretation of the geological setting of the previously discovered mineral deposits. The geology along the eastern margin of the H.Y.C. sub‐basin has been revised. The Cooley Dolomite Member of the Barney Creek Formation is interpreted as a talus‐slope breccia lying adjacent to a syndepositionally uplifted fault block (Western Fault Block) of lower McArthur Group sediments. The Western Fault Block was the source of the majority of the fragments in breccia horizons in the H.Y.C. sub‐basin and its uplift played an important role in the development of the sub‐basin. Within the Western Fault Block, the sequence hosting the Cooley II copper mineralization is the Mara Dolomite Member of the Emmerugga Dolomite, and not the Cooley Dolomite Member of the Barney Creek Formation as previously thought. New mineral discoveries include the substantial extension of the Coxco deposit, a coarse‐grained zinc‐lead stratabound deposit showing affinities with the Mississippi Valley‐type deposits; and an area of stratiform fine‐grained zinc‐lead mineralization in the Emu Plains sub‐basin of the Bulburra Depression.