Behavior of trace elements in quartz from plutons of different geochemical signature: A case study from the Bohemian Massif, Czech Republic

0392584 - GLÚ 2014 RIV NL eng J - Článek v odborném periodiku
Breiter, Karel - Ackerman, Lukáš - Svojtka, Martin - Müller, A.
Behavior of trace elements in quartz from plutons of different geochemical signature: A case study from the Bohemian Massif, Czech Republic.
Lithos. 175/176, 15 August (2013), s. 54-67. ISSN 0024-4937. E-ISSN 1872-6143
Grant CEP: GA ČR GAP210/10/1105
Institucionální podpora: RVO:67985831
Klíčová slova: Quartz * trace elements * granites * fractionation * Bohemian Massif
Kód oboru RIV: DD - Geochemie
Impakt faktor: 3.654, rok: 2013

The trace-element content in igneous quartz from granitoids of different geochemical types was investigated using the laser ablation ICP-MS technique. The Variscan granitoids in the Bohemian Massif provide an excellent opportunity to study the chemical composition of magmatic quartz from the following granite types: (1) geochemically primitive I-type tonalites and granodiorites, (2) peraluminous S-type two-mica granites, (3) moderately fractionated A-type volcano-plutonic complexes of the Teplice caldera, and (4) highly fractionated S- and A-type rare-metal granites. This diversity of granitoids permitted the study of the chemical composition of magmatic quartz as result of (i) different magma protoliths and (ii) variable degrees of differentiation. There were only small differences in the quartz trace-element contents, ranging from weakly to moderately differentiated plutons of all geochemical types: Al (mostly 20-250 ppm), Ti (mostly 20-110 ppm), B (<13 ppm), Be (<0.7 ppm), Ge (<1 ppm), Li (<30 ppm), and Rb (<2 ppm). Only the S-type granites from western Erzgebirge contain Al-enriched quartz (200-400 ppm Al) since the beginning of its evolution. However, quartz from the highly fractionated granites (group 4) differs significantly: it is poor in Ti (<20 ppm Ti) and enriched in Al (up to 600 ppm in A-type, and up to 1000 ppm in S-type granites), Be (up to 3.2 ppm), Ge (up to 5.7 ppm), Li (up to 132 ppm, particularly in the S-type granites), and Rb (up to 15 ppm). The input of Ti into quartz is controlled mainly by the temperature and pressure, the entry of Al into quartz increases as a function of the water and fluorine content of the residual melt. Ge and Li increase significantly with the fractionation of parental melt. Their concentrations are controlled by the order of crystallization of minerals: comb quartz crystallizing before Li-mica is strongly Li-enriched, whereas groundmass and snowball quartz crystallizing after mica is enriched in Ge.
Trvalý link: http://hdl.handle.net/11104/0221396