Mud and water geochemical characterization of the Nirano Mud Volcano (NMV, Fiorano Modenese, Italy)

Mud volcanoes (MVs) are surface expressions of subsurface processes characterized by movements of large masses of sediments and fluids, called “sedimentary volcanism” due to their morphological resemblance to igneous volcanoes [Martinelli & Judd, 2004, Mazzini & Etiope, 2017]. They are widely diffused and investigated since they are mostly located in petroliferous basins, although studied even by microbiology, geophysics, and structural geology, for their tectonic activity and as earthquake precursors [Martinelli & Judd, 2004]. Geochemical analyses focus mainly on gas composition, indeed, MVs are the second natural source of CH4 [Sciarra et al., 2019], while mud and water characterizations are almost absent in the literature. In Italy, MVs occur along the external compressive margins of the Northern (Pede-Apennine margin of Emilia Romagna) and Central Apennine and in Sicily [Candemi & Madonia, 2014, Sciarra et al., 2019]. Nirano mud volcano (NMV) of the Emilia Romagna region is one of the biggest in Italy, situated at the bottom of an oval depression, and the MV lies close to a small anticline in the outcrop of the Plio-Pleistocene “Argille Azzurre” clays [Minissale et al., 2000, Martinelli & Judd, 2004]. The area is characterized by several splatter-type grey gryphons, i.e., individual active vents, whose periodic overflows occur with sufficient frequency to avoid vegetation growth [Minissale et al., 2000, Mazzini & Etiope, 2017]. This work aims to characterize mud and water composition of this mud volcano. Preliminary ICP-MS and IC analyses for major ions (Na, Ca, Mg, K, Cl, NO3, NO2, F, PO3, SO4) on NMV waters agree with those found by Minissale et al. [2000], with EC of 2.30-15 mS, Cl 418-5370 ppm, and Na 196- 3426 ppm, indicating a contribution of both deep fluids and meteoric waters. For mud samples major, minor, and trace element composition will be determined through XRF, ICP-MS, EA-IRMS and stable isotopic (C, and S) analyses. References Cangemi M., and Madonia P., (2014). Mud volcanoes in onshore Sicily: a short overview. Göttingen Contributions to Geosciences, 77, 123-127. doi:10.3249/webdoc-3923 Martinelli G., Judd A., (2004). Mud volcanoes of Italy. Geological Journal, 39, 49-61. https://doi.org/10.1002/gj.943 Mazzini A., Etiope G., (2017). Mud volcanism: An updated review. Earth Science Reviews, 168, 81-112. https://doi.org/10.1016/j.earscirev.2017.03.001 Minissale A., Magro G., Martinelli G., Vaselli O., Tassi G.F., (2000). Fluid geochemical transect in the Northern Apennines (central‐northern Italy): fluid genesis and migration and tectonic implications. Tectonophysics, 319, 199-222. https://doi.org/10.1016/S0040-1951(00)00031-7 Sciarra A., Cantucci B., Ricci T., Tomonaga Y., Mazzini A., (2019). Geochemical characterization of the Nirano mud volcano, Italy. Applied Geochemistry, 102, 77-87. https://doi.org/10.1016/j.apgeochem.2019.01.006