Source-inherited compositional diversity in granite batholiths: The geochemical message of Late Paleozoic intrusive magmatism in central Calabria (southern Italy)

作者：Fiannacca Patrizia^*; Cirrincione Rosolino; Bonanno Fiorenza; Carciotto Manuele Mario

来源：Lithos, 2015, 236: 123-140.

DOI：10.1016/j.lithos.2015.09.003

• Granite petrogenesis
• Chemical variations
• Source composition
• Continental crust
• Serre Massif

The Serre Batholith, in central Calabria, is a Late Paleozoic granitoid complex that makes up the middle portion, ca. 13 km thick, of a continuous and nearly complete section of the continental crust. The batholith displays a large compositional variety, with granitoid rocks ranging with continuity from quartz diorite to syenogranite, a distinct group of leucotonalites also occur. The granitoids are on the whole magnesian and calcic to calc-alkalic, with only some of the more evolved rocks showing a ferroan calc-alkalic to alkali-calcic composition. Quartz diorites and tonalites are metaluminous to weakly peraluminous, while granodiorites and granites are weakly to strongly peraluminous, with two-mica porphyritic types being the only population with a genuine strongly peraluminous character. Fe*-number, MALI and ASI features highlight a strong affinity of the Serre Batholith rocks with Cordilleran granitoids, inherited from the compositions of the source rocks rather than reflecting the real tectonic environment of the magmas. Major trace element and existing Sr-Nd data are consistent with an origin of the Serre Batholith from the assembling of several batches of magmas with specific original compositions derived by fluid-absent melting of different crustal sources.
Quartz diorites and tonalites originated from a metabasaltic magma source, whereas metagraywackes with various mafic and pelitic contents appear the most likely sources of weakly peraluminous granodiorites and strongly peraluminous granodiorites and granites. Biotite +/- amphibole granodiorites could also have been derived from mafic-intermediate metaigneous sources. Two-mica porphyritic leucogranites are the only rock types representing pure crustal melts, resulting from melting of mafic pelitic sources. The other granitoid compositions are too silica-poor and MgO + FeOt rich to represent pure melts, so they need to include other components, such as solid restitic/peritectic material entrained from the magma source.
Mantle-derived magmas do not appear to have played a role in the geochemical diversity of the Serre Batholith granitoids; their inherited arc signature resulted from partial melting of crustal material of magmatic arc derivation, such as magnesian igneous rocks and sediments derived from their rapid erosion. This study suggests that post-collisional granitoid magmatism is likely not to be associated with the direct generation of new continental crust; all the granitoid rock types appear to represent recycled and reworked crustal material.

• 出版日期2015-11