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Chemical and mineralogical characteristics and origin of placer gold from fluvial deposits of Żeliszowski Creek (North Sudetic Basin, SW Poland)

Kania Marcin Łukasz

Geological Quarterly

2023

Vol. 67, No. 2

art. no. 12

Chemical and mineralogical analyses of individual detrital gold grains collected from recent channel-fill deposits of Żeliszowski Creek, located between the towns of Lwówek Śląski and Bolesławiec, were made, together with determination of the Au-bearing mineral assemblages and indication of probable source areas. The analysed gold grains have admixtures of silver, mercury and copper. Numerous inclusions of ore minerals, mainly Cu, Hg selenides and Cu, Pb and Bi sulphides were found in the detrital gold grains. These minerals are characteristic of Permian, Au-bearing, red-bed successions in the region, and of quartz veins of the Kaczawa Metamorphic Complex. This supports the hypothesis of a polygenetic origin for the Lower Silesian alluvial gold-bearing deposits. The applied research methodology may be successfully used in polymetallic ore deposit prospecting more generally.

Low-hafnium zircon from alluvial and colluvial placeres of northern Bohemia: composition and possible sorces

Ulrych J., Her P.

Geologia Sudetica

1999

Vol. 32, nr 2

139-146

Low-hafnium zircon is, together with pyrope, sapphire and magnesian ferri-ilmenite, a widespread heavy mineral in three historical placers of precious stones in N Bohemia. The chemical compositions of zircon from all three localities (Třebenice area, Jizerská louka Meadow, Sýkoří důl Valley) are appreciably similar. Zircon forms large, 1 to 7 mm long homogeneous or oscillatory zoned crystals, generally low in Hf (0.45-1.27; aver. 0.77 wt.% HfO2), Y, REE, U, Th and Ca. The genetic association of this zircon with nepheline syenite or pegmatite is doubtful as zircon from this rock found in xenoliths in a nearby alkali basalt pipe breccia from Košťálov Hill represents the Hf-rich type (1.57-1.97; aver. 1.73 wt.% HfO2). Consequently, low-hafnium zircon most probably originated from unknown coarse-grained products of early magmatic crystallisation of an alkali basalt magma forming explosive pipe breccias.