Paleomagnetic dating of non-sulfide Zn-Pb ores in SW Sardinia (Italy): a first attempt
Main Article Content
Abstract
A first paleomagnetic investigation aimed at constraining the age of the non-sulfide Zn-Pb ore deposits in the
Iglesiente district (SW Sardinia, Italy) was carried out. In these ores, the oxidation of primary sulfides, hosted
in Cambrian carbonate rocks, was related to several paleoweathering episodes spanning from the Mesozoic onward.
Paleomagnetic analyses were performed on 43 cores from 4 different localities, containing: a) non-oxidized
primary sulfides and host rock, b) oxidized Fe-rich hydrothermal dolomites and (c) supergene oxidation
ore («Calamine»). Reliable data were obtained from 18 samples; the others show uninterpretable results due to
low magnetic intensity or to scattered demagnetization trajectories. Three of them show a scattered Characteristic
Remanent Magnetization (ChRM), likely carried by the original (i.e. Paleozoic) magnetic iron sulfides. The
remaining 15 samples show a well defined and coherent ChRM, carried by high-coercivity minerals, acquired
after the last phase of counterclockwise rotation of Sardinia (that is after 16 Myr), in a time interval long enough
to span at least one reversal of the geomagnetic field. Hematite is the main magnetic carrier in the limestone,
whereas weathered hydrothermal dolomite contains goethite or a mixture of both. The results suggest that paleomagnetism
can be used to constrain the timing of oxidation in supergene-enriched ores.
Iglesiente district (SW Sardinia, Italy) was carried out. In these ores, the oxidation of primary sulfides, hosted
in Cambrian carbonate rocks, was related to several paleoweathering episodes spanning from the Mesozoic onward.
Paleomagnetic analyses were performed on 43 cores from 4 different localities, containing: a) non-oxidized
primary sulfides and host rock, b) oxidized Fe-rich hydrothermal dolomites and (c) supergene oxidation
ore («Calamine»). Reliable data were obtained from 18 samples; the others show uninterpretable results due to
low magnetic intensity or to scattered demagnetization trajectories. Three of them show a scattered Characteristic
Remanent Magnetization (ChRM), likely carried by the original (i.e. Paleozoic) magnetic iron sulfides. The
remaining 15 samples show a well defined and coherent ChRM, carried by high-coercivity minerals, acquired
after the last phase of counterclockwise rotation of Sardinia (that is after 16 Myr), in a time interval long enough
to span at least one reversal of the geomagnetic field. Hematite is the main magnetic carrier in the limestone,
whereas weathered hydrothermal dolomite contains goethite or a mixture of both. The results suggest that paleomagnetism
can be used to constrain the timing of oxidation in supergene-enriched ores.
Article Details
How to Cite
Boni, M., Dinarès-Turell, J. and Sagnotti, L. (2005) “Paleomagnetic dating of non-sulfide Zn-Pb ores in SW Sardinia (Italy): a first attempt”, Annals of Geophysics, 48(2). doi: 10.4401/ag-3202.
Issue
Section
OLD
Open-Access License
No Permission Required
Istituto Nazionale di Geofisica e Vulcanologia applies the Creative Commons Attribution License (CCAL) to all works we publish.
Under the CCAL, authors retain ownership of the copyright for their article, but authors allow anyone to download, reuse, reprint, modify, distribute, so long as the original authors and source are cited. No permission is required from the authors or the publishers.
In most cases, appropriate attribution can be provided by simply citing the original article.
If the item you plan to reuse is not part of a published article (e.g., a featured issue image), then please indicate the originator of the work, and the volume, issue, and date of the journal in which the item appeared. For any reuse or redistribution of a work, you must also make clear the license terms under which the work was published.
This broad license was developed to facilitate open access to, and free use of, original works of all types. Applying this standard license to your own work will ensure your right to make your work freely and openly available. For queries about the license, please contact ann.geophys@ingv.it.