Występowanie kasyterytu i złota rodzimego w aluwiach potoków w rejonie Leśnej (Sudety)

Abstract

CASSITERITE AND NATIVE GOLD IN ALLUVIAL DEPOSITS OF THE LEŚNA REGION (SUDETES)SummarySchlich survey of the Kwisa river tributaries has been made within the Leśna unit of the Izerski Block (Sudetes).In the north, the granitoid massif of the Karkonosze Mts., built up of porphyraceous granites,  biotites and porphyraceous aplogranites is covered with the Izerski Block. The massif is here a flat intrusion plunging under the Izerskie gneisses. The contact of the granite with the mantle rocks is of intrusive character.For the most part, the Izerski Block is built up of gneisses and gneissose granites; leucogranites, metamorphic schists and vein rocks such as microtonalites, microgranodiorites, granite porphyries, limburgites and quartz veins are found only subordinately. The occurrences of thin of cassiterite-sulphide type are related to the metamorphic schists. As a results of the schlich survey, high concentrations of cassiterite and traces of native gold have been found to occur in the alluvial of the Brusznik stream and of its tributaries. In the schlich samples, cassiterite occurs as sharply angular fragments 0.2–1.4 mm in size. Tin content in the schlich samples amounts to 57.6%. Native gold have been found in these samples as 7 grains, the size of which ranges from 1.0 to 2.0 mm.The features of cassiterite, the occurrences of this mineral in alluvial deposits with gold; and the topograhpical conditions of the area in study point to the fact that the tin-sulphate mineralization connected with the schist zone, making here the Kamienickie belt, could not have been source area to the cassiterite found in the alluvial deposits of the Brusznik stream. It is supposed on the basis of the facts so far ascertained that the quartz veins found in quantities in this area, were here primary source of cassiterite and of native gold.