Industrial minerals represent an important resource for the Italian economy, both in terms of exploitationand transformation, especially in those sectors for which Italy holds a leadership such as ceramics andglass. Among Italian regions Campania is one of the poorest of such kind of resources although some geologicalformations could be advantageously exploited. An important role is played by the deposits of sedimentaryzeolites linked to the activity of different volcanic districts occurring on the Neapolitan territory such as theCampanian Ignimbrite, the most important volcanic episode of the Campi Flegrei (Southern Italy), whichblankets a wide area of the Campanian region. The Campanian Ignimbrite has been thoroughly investigatedfrom a volcanological and petrographic point of view. However, little attention was devoted to the attainmentof those information useful to verify the potential of the deposit as well as the interpretation ofpost-depositional mineral-forming processes that have affected this deposit and have led to the formationof several facies, among which the most important are characterized by intense feldspathization (grey facies)and remarkable zeolitization (yellow facies).X-ray diffraction, X-ray fluorescence, inductively coupled plasma emission spectrometry and scanning electronmicroscopy methods were used to thoroughly characterize the entire set of samples collected from 31outcrops. Data so far acquired enabled to define the role played by several parameters (i.e., temperature, alkalineand alkaline-earth cations, etc.) in influencing the zeolitization process and the consequent crystallizationof phillipsite, chabazite, and analcime. Feldspathization appears to have been controlled mainly by theemplacement temperature of the deposits.The proposed genetic model involves emplacement of the pyroclastic flow in a single episode, producing adeposit with an upward-decreasing temperature gradient. In this model, the central portion had a temperatureinsufficient to cause significant feldspathization, and the upper portion of the formation was affected bywater percolation while still hot, producing progressive zeolitization.Volcano-stratigraphical parameters suggest some constrains on the maximum temperatures affecting thecentral portion of WGI.Thermodynamic data on zeolites constrain the maximum temperatures of the LYT unit which likely decreaseupwards in the unit up to ambient conditions in CPF.
|Titolo:||New insights into the mineralogical facies distribution of Campanian Ignimbrite, a relevant Italian industrial material|
|Data di pubblicazione:||2013|
|Appare nelle tipologie:||1.1 Articolo in rivista|