Naslov
Submarine volcanisam related hydrothermal alteration in the Darno-Sarvasko Units (NE Hungary), and in the Dinarides and Hellenides.

Autori
Kiss, Gabriella ; Molnar, Ference ; Bartha, A. ; Palinkaš, Ladislav

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Acta Pineralogica Petrographica, Abstract Series / Zaharia, L., Kis, A., Topa, B., Papp, G., Weiszburg, T. G. - Segedin : University of Szeged, 2010, 538-538

Skup
IMA 2010

Mjesto i datum
Budimpešta, Mađarska, 25.08.2010. - 29.08.2010

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
Submarine volcanisam; hydrothermal alteration; geochemistry

Sažetak
Comparative studies on hydrothermal alteration were carried out on submarine basaltic volcanites with different origin. Peperitic basalt occurrences related to the Triassic early rifting of the Neo-Tethys were studied in displaced parts of the Dinarides (Darnó Unit, NE-Hungary) as well as in the Dinarides (Kalnik Mts, Croatia, Vares- Šmreka, Bosnia-Herzegovina) and in the Hellenides (Stragopetra Mts.), while Jurassic basalts formed in an intra-oceanic back-arc-basin of the Neo-Tethys (Darno Unit, Hungary). Within the submarine basaltic lava units 7 volcanological facies were distinguished and these bear different types of hydrothermal alteration. Alteration 1 is characterized by albitization of the rock-forming plagioclase at ~300°C and occurs both in the Triassic and Jurassic rocks. Superimposing alterations (alteration 2) were developed during cooling from 280°C to ~140°C (Jurassic rocks) and ~70°C (Triassic rocks) temperature. During the higher temperature part of these processes chlorite formed in the ground mass, however chlorite and rarely quartz formed in the micro fractures and small amygdales of the Triassic basalts, while chlorite, quartz and prehnite precipitated in the micro fractures of the Jurassic rocks. At lower temperatures calcite formed commonly in the larger amygdales, jig-shaw type veins and as other infillings. Some epidote, pumpellyite, prehnite and laumontite also occur in the Triassic basalts, while datolite is a rare mineral in the Jurassic ones. During this process the system was mainly seawaterdominated because fluid inclusions are characterised by 3.2-7.8 NaCl equ. wt% salinities. Late stage alteration 3 is characterised by argillitization occurring at every studied locality ; presence of disordered layer silicate (smectite group) is proven by XRD. Though similar processes happened at the Triassic and Jurassic localities, relatively limited fluid- rock interaction was characteristic to the Jurassic basalts, which resulted in minerals formed at higher temperatures and limited amount of hydrothermal infillings (no amygdales or other infillings occur, only short veins). On the ground of extended petrochemical study, mobilization of the different elements was followed even in single pillow lava-scale, inside a volcanic facies from fresher to more altered parts and between different facies as well. Mass transfer calculation was made to determine the gains and losses which refer to the (1) and (3) alterations, while results of (2) were mainly eliminated (except ground mass chloritization). Increase of Na2O (i.e. albitization) is haracteristic in a pillow from core to rim, though results of low temperature alteration (decrease in SiO2, MgO) can also be seen. Examining the processes from fresher to more altered part of a facies the (3) alteration mainly overprint the (1). At distal volcanic facies (such as peperitic basalt and pillow fragmented hyaloclastite breccia) the low temperature alteration and the formation of clay minerals are more dominant, though at the hyaloclastite breccia high grade chloritization is also dominant (increase in MgO). The effect of the basalt on the peperitic limestone is characterized with elevated Cr, Ni, Co, Cu in the sediment, while presence of the limey mud during the cooling of the lava resulted in stronger alteration processes in the contact basalt.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

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