The source rocks in the North and South had rather unradiogenic Sr 526 and 571 Ma ago, respectively. At R_i≲0.7066 all presently known Damaran metasediments and metavolcanics as well as the basement must be excluded as the protoliths. A hypothetical source with a large proportion of low (⁸⁷Sr/⁸⁶Sr) volcanic material is required. In the center, on the other hand, the Sr isotope ratios are more radiogenic and derivation from common Damaran metasediments is a distinct possibility. Keywords: Source Rock,  Isochron, Intrusive Granite, Isotope Homogenization, Hypothetical Source.