These sections fulfill most of the requirements for a GSSP, and their biozone boundaries can be correlated precisely with each other. It has excellent and well-known graptolite and conodont biostratigraphy in a stratigraphically continuous succession of uniform lithology, is readily accessible, and the key interval is not affected by faulting. Although having some drawbacks, the Calera and Dawangou boundary sections are likewise excellent in most significant respects and they are proposed to be selected as auxiliary stratotypes. Xu Upper Palaeozoic intracontinental massive sulphide deposits occur in both the Lower Yangtze River and the Nanling Mountain regions of South China. However, sulphide ores of these two regions are remarkably different in composition.
Fluid inclusions are highly saline and sodium-rich.
Their fluid inclusions have low salinities and are potassium-rich. There is evidence to indicate that the Upper Palaeozic continental crust in the Lower Yangtze region has lower maturity than that of the Nanling Mountain region. The compositional contrasts between these two regions are suggested to have been controlled by differences in their basin basements and thus reflect the difference in crustal maturity during ore formation. The volcanic shoshonitic associations in Iran are limited to volcanic belts of Eocene to Recent volcanism. Petrographic studies of 205 samples of Iranian volcanic rocks indicate that those of the shoshonitic association are mainly composed of olivine, clinopyroxene, plagioclase, biotite, sanidine, analcime, leucite, magnetite and apatite.