TURBIDITE GEOCHEMISTRY AND PROVENANCE STUDIES IN THE SOUTHERN UPLANDSOF SCOTLAND

Regional Lithogeochemical data from the Southern Uplands have been use d to characterize a distinctive stratigraphy across this region. A sui te of 840 point-counted and petrographically classified greywacke samp les were used to establish chemical fingerprints for a series of greyw acke-dominated lithostratigraphical units. These fingerprints were the n used to evaluate a further 1455 greywacke samples collected througho ut the Southern Uplands and Longford Down and enabled a series of stri ke-parallel geochemical tracts to be defined. Four principal geochemic al groups are recognized, relating to cratonic- and volcanic-derived g reywacke provenances and both carbonate-rich and hydrothermally altere d greywackes. Volcanic-derived units display higher Ti, Fe, Mg, Ca, Na , Mn, Cr, Ga, Ni, Sr, V and Zn values than their cratonic counterparts , which, with the exception of the carbonate-rich Hawick Group, displa y higher Si, K, La, Nb, Rb, Th and Zr. Volcaniclastic greywackes displ ay REE patterns dissimilar to typical post-Archean upper crust, but si milar to their andesitic components, whereas cratonic groups have REE patterns close to that of upper crust. Systematic strike-parallel geoc hemical variation in the Southern Uplands is controlled by petrographi cal differences which directly reflect provenance, with individual lit hostratiphical units derived from variable mixtures of ophiolitic, cal c-alkaline, acid-igneous, low-grade metamorphic and carbonate-rich det ritus.