TY - JOUR
T1 - Nature and development of supergene manganese deposits, Groote Eylandt, Northern Territory, Australia
AU - Pracejus, Bernhard
AU - Bolton, Barrie R.
AU - Frakes, Larry A.
N1 - Funding Information:
This paper was presenteda t a field workshop of IGCP Project 226 held on Groote Eylandt in September 1986. Appreciation is expressedt o the Groote Eylandt Mining Company for providing accommodation and working facilities and to B.H.P. Co. Ltd. for financial support. We wish to thank staff members of both companies for their helpful and critical discussions.
PY - 1988/11
Y1 - 1988/11
N2 - Supergene manganese ores occur on Groote Eylandt in association with other secondary rocks. Overprinting primary sedimentation features (e.g. oolitic and pisolitic units), secondary Mn-oxides and gangue minerals nowadays belong to the most important components in the deposits. The different primary and supergene rock types are described and discussed with the help of typical geological profiles. In an idealized vertical cross section we present a combination of all observed supergene Mn-ores ("mangcretes"). Many parts of this section can be encountered in various localities of the Groote Eylandt deposits. The most common minerals found on the island are pyrolusite, cryptomelane, romanechite (psilomelane), todorokite, quartz, kaolinite, goethite and hematite. Probably with the exception of todorokite, all other mentioned phases can occur as primary and/or supergene minerals. The dominant process for the dissolution of Mn-oxides is a redox reaction between divalent iron and tetravalent manganese. Other leaching processes are of subordinate importance. We discuss transport and precipitation which lead to the development of a "Mangcrete Model" for supergene Mn-deposits. Finally the supergene products are compared with secondary ores of other manganese deposits and it can be seen that in spite of different protores the supergene materials can be very similar in their physical appearance and mineralogy.
AB - Supergene manganese ores occur on Groote Eylandt in association with other secondary rocks. Overprinting primary sedimentation features (e.g. oolitic and pisolitic units), secondary Mn-oxides and gangue minerals nowadays belong to the most important components in the deposits. The different primary and supergene rock types are described and discussed with the help of typical geological profiles. In an idealized vertical cross section we present a combination of all observed supergene Mn-ores ("mangcretes"). Many parts of this section can be encountered in various localities of the Groote Eylandt deposits. The most common minerals found on the island are pyrolusite, cryptomelane, romanechite (psilomelane), todorokite, quartz, kaolinite, goethite and hematite. Probably with the exception of todorokite, all other mentioned phases can occur as primary and/or supergene minerals. The dominant process for the dissolution of Mn-oxides is a redox reaction between divalent iron and tetravalent manganese. Other leaching processes are of subordinate importance. We discuss transport and precipitation which lead to the development of a "Mangcrete Model" for supergene Mn-deposits. Finally the supergene products are compared with secondary ores of other manganese deposits and it can be seen that in spite of different protores the supergene materials can be very similar in their physical appearance and mineralogy.
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U2 - 10.1016/0169-1368(88)90005-4
DO - 10.1016/0169-1368(88)90005-4
M3 - Article
AN - SCOPUS:0024106785
SN - 0169-1368
VL - 4
SP - 71
EP - 98
JO - Ore Geology Reviews
JF - Ore Geology Reviews
IS - 1-2
ER -