Petrography and Geochemistry of the Leucocratic Rocks in the Ophiolites from the Pollino Massif (Southern Italy)

Giovanna Rizzo,Luigi Bloise,Roberto Buccione,Rosa Sinisi,Egidio Calabrese,Salvatore Laurita,Giovanni Mongelli,Michele Paternoster

doi:10.3390/min11111264

Abstract

In the Tethyan realm, leucocratic rocks were recognized as dikes and layers outcropping in the ophiolitic rocks of the Western Alps, in Corsica, and in the Northern Apennines. Several authors have suggested that the origin of leucocratic rocks is associated with partial melting of cumulate gabbro. Major and trace elements composition and paragenesis provided information about the leucocratic rocks genetic processes. This research aims at disclosing, for the first time, the petrographical and geochemical features of Timpa delle Murge leucocratic rocks, Pollino Massif (southern Italy), in order to discuss their origin and geodynamic significance through a comparison with other Tethyan leucocratic rocks. These rocks are characterized by high amounts of silica with moderate alumina and iron-magnesium contents showing higher potassium contents than plagiogranites, due to plagioclase alteration to sericite. Plagioclase fractionation reflects negative Eu anomalies indicating its derivation from gabbroic crystal mushes. The chondrite normalized REEs patterns suggest the participation of partial melts derived from a metasomatized mantle in a subduction environment. The results reveal some similarities in composition with other Tethyan leucocratic rocks, especially those concerning Corsica and the Northern Alps. These new data provide further clues on the origin of these leucocratic rocks and the Tethyan area geodynamic evolution.

Highlights

Several authors [2,3,4,5,6,7] have proposed that these rocks derive from fractional crystallization of MORB-type basaltic magmas at low pressures, such as the Oman and Troodos ophiolitic sequences [8]
Other authors [9,10,11] have instead suggested an origin associated with partial melting of cumulate gabbro [10,12,13] while further authors [3,14] suggested that these rocks formed by presence of immiscible liquids found together with mafic melts
The samples consist of leucocratic rocks and show equigranular, medium to coarse grained texture (Figure 4)

Summary

Introduction

This research aims at disclosing, for the first time, the petrographical and geochemical features of Timpa delle Murge leucocratic rocks, Pollino Massif (southern Italy), in order to discuss their origin and geodynamic significance through a comparison with other Tethyan leucocratic rocks. These rocks are characterized by high amounts of silica with moderate alumina and iron-magnesium contents showing higher potassium contents than plagiogranites, due to plagioclase alteration to sericite. The results reveal some similarities in composition with other Tethyan leucocratic rocks, especially those concerning Corsica and the Northern Alps These new data provide further clues on the origin of these leucocratic rocks and the Tethyan area geodynamic evolution.

Objectives

Methods

Results

Conclusion