Fluorine contents in carbonate sequences and rare earths distribution in fluorites of Pb-Zn deposits in East-Alpine Mid-Triassic

摘要

To divulge plausible source for fluorine in the Upper Ladinian of the East Alpine geosyncline, two totally independent geochemical approaches have been made. They are (i) correlation study of the stratabound, stratiform, paleographic and regional fluorine anomalies observed in seven selected profiles of the carbonate sequences and (ii) comparative study of the distribution of rare earths (REE) in fluorspars from northern and southern Ladinian sequences. The fluorine anomalies in the entire East Alpine geosyncline were found to be confined only to a few horizons which could be stratigraphically correlated. The fluorspars of the Nördliche Kalkalpen showed REE distribution characteristic of a sedimentary formation while those of the Südliche Kalkalpen (Bleiberg area) apparently showed a hydrothermal type of REE distribution. These and various other considerations discussed in the present paper go to show that a relatively short-termed submarine exhalative source (volcanic) of a recurring nature in the Ladinian stage of the Mid-Triassic might have been plausibly responsible for the supply of fluorine found in the carbonate sequences of the East Alpine geosynclines. The noted stratigraphic correlation of fluorine anomalies suggested, in addition, that fluorine bearing layers could be used as temporaneous marker beds. An interesting side observation was that of the bi-to tri-modal fluorine distribution in four profiles which represented well mineralized areas in contrast to the unimodal fluorine distribution in the rest three profiles with no distinct zone of mineralization. Probably such a multimodal distribution of fluorine may be characteristic of the Pb-Zn deposits (or other ore bearing-units) in paragenesis, granted which, it may find application as proximity indicators of ore deposit