Citation: Buccione, R.; Rizzo, G.; Mongelli, G. Geochemistry as a Clue for Paleoweathering and Provenance of Southern Apennines Shales (Italy): A Review. Minerals 2023, 13, 994. https://doi.org/10.3390/ min13080994 Academic Editor: Georgia Pe-Piper Received: 28 June 2023 Revised: 22 July 2023 Accepted: 24 July 2023 Published: 26 July 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). minerals Review Geochemistry as a Clue for Paleoweathering and Provenance of Southern Apennines Shales (Italy): A Review Roberto Buccione * , Giovanna Rizzo and Giovanni Mongelli Department of Sciences, University of Basilicata, 85100 Potenza, Italy; giovanna.rizzo@unibas.it (G.R.); giovanni.mongelli@unibas.it (G.M.) * Correspondence: roberto.buccione@unibas.it Abstract: The southern Apennines (Italy) chain is a fold-and-thrust belt mainly derived from the deformation of the African–Apulian passive margin where shallow-water, basinal, and shelf-margin facies successions, including fine-grained sediments, occur. Here, we provide a review of the geochemistry of Meso–Cenozoic shales from the Lagonegro basin to elucidate provenance and paleoweathering. The different suites of these shales are dominated by 2:1 clay minerals and are Fe shales and shales. An R-mode factor analysis suggests Ti, Al, and LREE (F1) and K 2 O-MgO (F2) covariance, likely related to the illite → smectite → kaolinite evolution during weathering. HREE and Y are distributed by phosphate minerals, suggesting LREE/HREE fractionation. The CIA paleoweathering proxy rules out non-steady-state weathering conditions and indicates that the source area was affected by moderate to intense weathering. The paleoprecipitation values derived from the CIA-K and CALMAG indices show median values in the 1214–1610 mm/y range. The Eu/Eu*, Sm/Nd, and Ti/Al provenance ratios point toward a UCC-like source excluding any mafic supply and suggest that the Lagonegro basin was connected, through a southern area, with the African cratonic area. However, the Eu/Eu* median value of the southern Apennine shales is quite similar to the value of the Archean shales, possibly indicating a less differentiated component. This is consistent, in many samples, with the value of the (Gd/Yb) ch ratio, suggesting that the shales likely incorporated ancient sediments derived from African Archean terranes through a cannibalistic process. Keywords: geochemistry; Apennine shales; trace elements; rare earth elements; factor analysis; paleoclimate 1. Introduction The chemical composition of siliciclastic sedimentary rocks is an important record of the geological evolution of the continental crust through time, because some elements are quantitatively transported in the terrigenous fine fraction [1]. Of these, the rare earth elements (REEs) are the most useful because their distribution is not affected by secondary processes, and the REE patterns of fine-grained siliciclastic sediments and some elemental ratios, especially Eu/Eu*, are assumed to reflect the exposed crustal abundance in the source area [2–9]. However, weathering conditions affect the leaching of elements during the path from the protolith(s) to the sediment(s). Low-field-strength elements have a high affinity for aqueous phases, although some of them can be further partially incorporated into secondary clay minerals (see [10,11], and references therein). Mobile elements can be used to evaluate the degree of chemical weathering [12–16] and to characterize the paleoclimate and paleoprecipitation [17–23]. Consequently, the distributions of both selected major and trace elements in fine-grained siliciclastic sediments are widely used to constrain the provenance, paleoweathering, and paleoclimate conditions. The evolution of the geology of the Mediterranean area includes peculiar phenomena, such as continental rifting during the Triassic, oceanic spreading in the Jurassic–Early Cretaceous, the closure of the Tethys from the Late Cretaceous to the Tertiary, and finally, the continental collision between the Adriatic–African plate and the European plate. This Minerals 2023, 13, 994. https://doi.org/10.3390/min13080994 https://www.mdpi.com/journal/minerals