Gas Manifestations in Central Italy

Abstract

Two families of natural gases are present in central Italy. One is and is related to thermal waters that can circulate to depth in Mesozoic carbonate formations and can mix with descending air-saturated meteoric waters in their outcrop areas. The second is and comprehends gas emissions emerging in dry conditions or associated with cold stagnant waters. In many of the waters, and and the seems to derive, partly, from metasedimentary rocks belonging to the regional Paleozoic thermal springs. In this study we present preliminary results of a new chemical survey on manifestations in central Italy by analyzing bulk composition and and new (the latter both in and isotopic ratios in 60 samnles homogeneously distributed over the area in Fig. 1. distribution, has been considered either the product of hydrolysis of carbonate formations in the 100-250 range of temperature Based on values in and their areal of central Italy isotopic ratios range from 1.0 to 2.5 and in ranges from -3.0 to -10.0 suggesting a certain contribution of mantle-derived gases in the vapor-dominated areas of Larderello and Travale. In the southern part of central Italy, gases seem to have a more shallow origin. values well below 1.0, and in C02 around zero, point to a crustal origin for the risinq gas where C02 seems to derive, prevalently, from thermometamorphism of the Mesozoic carbonate formations.