| More

MANGANESE MINERALISATIONS AT THE BASE OF MIOCENE SEDIMENTS IN NORTHERN SARDINIA (ITALY)

Views: 118 Downloads: 122
S. Fadda, M. Fiori, S. Pretti, P. Valera
S. Fadda, M. Fiori, S. Pretti, P. Valera

Abstract


During the eastward drift of the Palaeozoic-Mesozoic block formed by Sardinia and Corsica in the Oligocene-Miocene, calc-alkaline volcanism developed mostly in the western part of the island. Most Tertiary metallogenic phoenomena are related to hydrothermal activity associated with this volcanism. Following volcanic and related hydrothermal activity, sediments were deposited during the Oligocene-Miocene as a consequence of a marine transgression. The basal part of this series is clastic and includes elements derived from erosion of unaltered volcanics as well as hydrothermally altered rocks and hydrothermal vein quartz. Inside the Tertiary volcanics manganese ore-minerals occur as nodules, veinlets, and stockworks and mainly include Mn and Fe oxides; quartz in different forms is the most common gangue mineral. The mineralisations at the contact between volcanics and Miocene sediments are the most homogeneous, the ore-minerals occur in the cement, but also as fairly continuous thin beds, nodules and veinlets containing pyrolusite, frequent ramsdellite, less frequent manganite, psilomelane, cryptomelane-manjiroite, rare ranciéite, and todorokite. The nature of the ore-bearing beds indicate a near-shore clastic environment along the ancient coastal lines of the Miocene sea. Genetic considerations point to a supergenic transport and redeposition after erosion of primary dispersion and residual concentrations of Mn in the volcanics.


Keywords


sedimentary manganese; volcanis; metallogeny Sardinia;

Full Text:

PDF

References


Biondi E., Filigheddu, P., 1990. A palm fossil closely related to Chamaeropos humilis L. from the Lower

Miocene of Sardinia. Giorn. Bot. Ital. 124, 711-724.

Cherchi, M. A., Montadert, L., 1982. Il sistema di rifting Oligo-Miocenico del Mediterraneo occidentale

e le sue conseguenze Paleogeografiche sul Terziario Sardo. Mem. Soc. Geol. Ital. 24, 387-400.

Coulon, C., 1977. Le volcanisme calco-alcalin Cénozoicque de Sardaigne (Italie): Pétrographie, géochimie,

et genèse des laves andesitiques et des ignimbrites: Signification géodinamique; Thése, Université

de Droit, D’Economie et des Sciences D’Aix, Marseille.

Garbarino, C., Grillo, S. M., Marcello, A., Pretti, S., Uras, I., Fiori, M., 1991. First data on Tertiary epithermal

occurrences in Sardinia, Italy. Proc. Symp. Braz. Gold 91, Belo Horizonte, 143-150.

Lentz, D.R., 2003. Geochemistry of Sediments and Sedimentary Rocks: Evolutionary Considerations to

Mineral Deposit-Forming Environments. Ed. Lentz, D.R., 184pp.

Jambor, J., L., & Blowes, D.,W., 1994. Short course handbook on environmental geochemistry of sulfide

mine-wastes. Waterloo Ontario, May,1994; Ed. Jambor, J., L., & Blowes, D.,W., 22, 438.

JCPDS File, 1985. Powder diffraction file: Inorganic phases. JCPDS International Centre for Diffraction

Data, PA, USA, 998 pp.

(5) XLIII, No 5 – 2595

Maynard, J., B., 1983. Geochemistry of Sedimentary Ore Deposits. Springer-Verlag, New York, Heidelberg,

Berlin, 305 pp.

Marcello, A., Pretti, S., Valera, P., Fiori, M., 2004. Tertiary manganese occurrences in Sardinia (Italy).

Proccedings of the interim IAGOD Conference, Vladivostok, Russia, 487-490.

Martini, I., P., Oggiano, G., and Mazzei, R., 1992. Siliciclastic-carbonate sequences of Miocene grabens

of northern Sardinia, western Mediterranea Sea. Sedimentary Geology, 76, 63-78.

Mazzei, R., Oggiano, G., 1990. Messa in evidenza di due cicli sedimentari nel Miocene dell’area di Florinas

(Sardegna settentrionale). Atti Soc. Tosc. Sci. Nat., Mem. Seie A., 97, 119-147.

Pettijohn, F., J., Potter, P., E., & Siever, R., 1972. Sand and sandstones. Springer-Verlag, New York-Heidelberg-

Berlin, 618 pp.

Redini, R., 1940. Sul wolframio connesso a minerali manganesiferi e sull’età di talune formazioni terziarie

della Sardegna settentrionale. Boll. R. Uff. Geol. d’It., 65, 44 pp.

Roy, S. 1981. Manganese Deposits. Academic press., 418 pp.

Sapozhnikov, D., G.,1970. Manganese Deposits of the Soviet Union. Ed. Sapozhnikov, D., G., 522pp.


Refbacks

  • There are currently no refbacks.


Copyright (c) 2017 S. Fadda, M. Fiori, S. Pretti, P. Valera

Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.