Preliminary microthermometric data on the Uludağ W-skarn deposit, Bursa, NW Turkey

HANİLÇİ N., AYSAL N., Ceyhan A., Şenkaya S.

11th Pan-American Current Research on Fluid Inclusions Conference, Canada, 1 - 04 June 2012, pp.37-38

  • Publication Type: Conference Paper / Full Text
  • Country: Canada
  • Page Numbers: pp.37-38
  • Istanbul University Affiliated: Yes


Uludağ is located in northwest Turkey. The basement of the Uludağ Massive comprises Paleozoicaged
medium to high grade metamorphic rocks, such as amphibolites, gneisses and marbles. This
metamorphic basement has been cut by Oligocene-aged (Okay et. al., 2008) Uludağ granodiorite. The
Uludağ granitoid has modal compositions that are generally granodioritic, as do two outcropping stocks
(two mica granodiorite and coarse-grained biotite granodiorite). The granitoid contains a number of
xenoliths of the surrounding basement rocks with extensive metamorphic textures with amphibolitic
composition (Yurdagül, 2004). The skarn zone has been developed along the granodiorite and marble
contact. From the contact outward, the exoskarn zone comprises andradite, andradite+diopside, and
diopside skarn zones, respectively. The skarn zones are enveloped by a tremolite-actinolite hornfels
zone. The endoskarn zone has developed in a narrow area within the granodiorite and comprises epidote
and hedenbergite. Quartz veins cut the skarn zones, represent a later hydrothermal event, and are host
to W-mineralization. The aim of this study is to characterize the nature of the solutions that were
responsible for the formation of the Uludağ skarn and the W-mineralization. For this purpose, the skarn
zone has been sampled for fluid inclusion studies from the contact outward (Fig. 1).
zone and quartz from the veins. At room temperature, two types of fluid inclusions were defined: type LV
(liquid-vapor) and type LVS (liquid-vapor-solid) in the garnet and quartz minerals. The measurements
were carried out on the primary inclusions, which occur as small clusters isolated in the garnet and
quartz. The morphology of the inclusions is mostly irregular and they tend to be elongated in garnet, and
mostly regularly-shaped in quartz. From the microthermometric results, the Te was between -43°C and -
34°C for LV type in garnet, and between -58°C and -36°C for LV type in quartz. The average TmICE value
for LV type inclusions in garnet was -6.85°C, corresponding to 10.3 wt% NaCl equivalent, and the TmICE interval for LV type inclusions in quartz was between -12°C and -3°C, corresponding to 16 and 5 wt%
NaCl equivalent. In some LV type inclusions in quartz, melting occurred between +8oC and +9oC,
indicating the presence of CO2 in the system. The average homogenization temperature of the LV type
inclusions is 435°C for garnet, and 351°C for quartz. Generally, the solid phase (halite) of the LVS type
inclusions did not melt until 600°C. Melting of halite was observed in only two LVS type inclusions in
garnet at 545°C and 550°C, indicating a salinity of 65 wt% NaCl equivalent.
Preliminary microthermometric data indicate that the Uludağ skarn formation started at conditions over
600°C with high salinity (at least 65 wt% NaCl equiv.) solutions. The salinity of the solution dropped to 5%
wt% NaCl equivalent with decreasing temperature to an average of 351°C during the late stage of the
skarn formation, which is characterized by quartz veins and W-mineralization.
Okay, A.,I., Satir, M., Zattin,M., Cavazza, W., Topuz, G. (2008) An Oligocene ductile strike-slip shear zone: The
Uludağ Massif, northwest Turkey - Implications for the westward translation of Anatolia. Geological Society of
America Bulletin. Vol. 120. 893-911.
Yurdagül, A. (2004) Lithogeochemical Investigation of the Uludağ Granitoide. Unpublished MSc thesis. Istanbul
University, Institute of Science. 140p.