Geochemical implications for the magma origin of granitic rocks from the Ditrău Alkaline Massif (Eastern Carpathians, Romania)

Abstract

In addition to a series of ultramafic to mafic and alkaline igneous rocks, a granite body also occurs in the Ditrău AlkalineMassif, Eastern Carpathians, Romania. We present and discuss mineral chemical data, and major and traceelement compositions of the granites in order to define their nature and origin and to determine the depth of the magmaemplacement. The granites consist of K-feldspar, albite to oligoclase and quartz accompanied by Ti-rich annite± calcic amphiboles. Depending on the amphibole content they are classified as less fractionated amphibole-bearingand amphibole-free varieties. Accessories include zircon, apatite, magnetite, ilmenite, and allanite or monazite.High Zr, Nb, Ga, Ce and Y content and Ga/Al and Fe/Mg ratios, together with low CaO, Sr and Ba contents and Y/Nbratios of 0.04-0.88 are consistent with A1-type granites and mantle differentiates correspond to an intra-plate environment.The Ditrău Alkaline Massif granites were emplaced at middle – upper crustal levels between 14 and 4 km depthas indicated by the calculated crystallization pressure of 370 ± 40 MPa and the stability limit of calcic amphiboles. 

Keywords

• A-type granite
• geochemistry
• mantle differentiates
• amphibole geobarometry
• Ditrău Alkaline Massif