GEOCHEMICAL CHARACTERISTICS AND RARE-EARTH ELEMENT DISTRIBUTIONS OF KOZBUDAKLAR W-SKARN DEPOSIT (BURSA, WESTERN ANATOLIA)

The Kozbudaklar W-skarn deposit occurs along the contact between Eocene Topuk granitoid and Triassic İnönü marble in Tavşanlı Zone. In the study area, the endoskarn is represented by plagioclase-pyroxene and exoskarn zone which is characterized by pyroxene, pyroxene-garnet, garnet and garnet-pyroxene skarn facies. According to major oxide element contents, exoskarn is of calcic character. In pyroxene and pyroxene-garnet skarn facies, tungsten and molybdenum abundances vary between 434-5507 ppm (mean 2330 ppm) and 8 - 90 ppm (mean 40 ppm). In the garnet and garnet-pyroxene skarns, concentrations of these elements are 271 - 7616 ppm (mean 2486 ppm) and 7 - 493 ppm (mean 107 ppm), respectively, and molybdenum concentration is increased. ƩREE contents of the Topuk granitoid, endoskarn, exoskarn and İnönü marble are in the range of 75.8 to 158.9 ppm (mean 106.2 ppm), 75.8 to 171.5 ppm (mean 114.6 ppm), 3.5 to 290.8 ppm (mean 48.7 ppm) and 2.3 to 15.3 ppm (mean 6.1 ppm), respectively. Although ƩREE concentrations of skarn zones are higher than those of Topuk granitoid and İnönü marble, ƩREE concentrations of tungsten-rich samples are signifi cantly depleted. In areas of scheelite mineralization, REE trends and Eu anomalies display two different patterns. REE trends, HREE enrichments and negative Eu anomalies of pyroxene and pyroxene-garnet skarn facies exhibit similarities with Topuk granitoid. In these skarn facies, tungsten-rich samples are represented by a Ce depletion and low Eu/Eu* (Eu/Eu* = 0.56-0.88). Garnet and garnet-pyroxene skarn facies are characteristic with a convex LRRE pattern, maximum Pr and Nd concentrations and positive Eu anomalies. Ce-enrichment and high Eu/Eu* ratios (Eu/Eu* = 1.45 - 4.18) are observed in tungsten-rich samples. Considering the molybdenum enrichments and REE pattern, scheelite mineralization in the Kozbudaklar W-skarn deposit can be said to have developed at two different high temperature phases. In the fi rst-phase mineralization was formed by early magmatic fl uids under moderate oxidant conditions whilst the second-phase scheelite mineralization was formed under increasing oxidant conditions.