Reply to the comment by J. Hergt on the paper “Enriched mantle - Dupal signature in the genesis of the Jurassic Ferrar tholeiites from Prince Albert Mountains (Victoria Land, Antarctica)” by Antonini et al. (Contributions to Mineralogy and Petrology 136: 1-19, 1999).

1. The AFC model proposed in the paper by Antonini et al. (1999) explains the whole geochemical variation of Ferrar rocks from Prince Albert Mountains, and was not essentially devoted to reproduce the geo- chemical features of the least evolved investigated sample (LZ11B). 2. The ``primary'' Ferrar basalt reported in Antonini et al. (1999), representative of E-MORB type source, fits the compositional variability of the Dupal type E-MORB. 3. In general the low Ti coupled with the high LREE of the LZ11B sample can be reproduced within 15±20% error by an AFC model (r = 0.3; f = 0.7) involving a "diluted'' Dupal type E-MORB composition and the granulites used in the paper by Antonini et al. (1999). The differences between the calculated and observed P/Nd, La/Nb and Ti/Y may reflect the geochemical variability of Victoria Land granulites. 4. The available data indicate that an E-MORB mantle source coupled with AFC is appropriate to explain the observed low TiO2 and high LREE contents, without involving an N-MORB source contaminated by PAAS, which requires two steps of crustal contamination, the first in the source mantle and the second during magma uprising. 5. A petrogenetic model able to explain all the geo- chemical features of Ferrar rocks has not been ob- tained yet and therefore the origin of crustal signature in the least evolved Ferrar tholeiites is still an open question. However, we have demonstrated that an E-MORB Dupal type mantle source appears ap- propriate to reproduce the Victoria Land's tholeiites whose "crustal signature'' is mainly due to low- pressure contamination through crystalline basement materials

Enriched mantle - Dupal signature in the genesis of the Jurassic Ferrar tholeiites from Prince Albert Mountains (Victoria Land, Antarctica)

The major, trace (including rare earth) element abundances, and Sr-Nd-Pb isotopic compositions, have been analysed for andesitic basalt and andesitic sills and lavas of the Jurassic Ferrar Magmatic Province, Prince Albert Mountains, Antarctica. The typical “crustal signature” of the Ferrar magmatism, characterized by relatively high SiO2, LREE and LILE contents in these samples, is associated with high 87Sr/86Sr and low 143Nd/144Nd. Systematic correlations of major and trace elements indicate that fractional crystallization was important. However, increases in incompatible elements are positively correlated with initial 87Sr/86Sr, suggestive of crustal assimilation processes. The observed correlations between initial 87Sr/86Sr and LREE enrichments have been modelled by an AFC process, starting from the least evolved sample and assuming the compositions of the orthogranulites of Victoria Land as contaminants. The REE patterns of the least evolved Ferrar rocks approach those of E-type MORB, differing only by higher LREE/IREE. The enrichment in LREE, accompanying high initial 87Sr/86Sr, 207Pb/204Pb and low 143Nd/144Nd compared with E-type MORB, can be explained by interaction of “primary Ferrar basalt” with crystalline basement. We propose a petrological model whereby Ferrar magmas were generated through high degrees of melting of an E-type MORB mantle source, and subsequently these “primary” melts underwent AFC processes inheriting a crustal signature. The Sr-Nd-Pb isotopic compositions required by the AFC model for the primary Ferrar basalt are similar to those of the Dupal signature of the oceanic basalts of the Southern Hemisphere (Hart 1984). Transantarctic Mountains would have been located inside the Dupal anomaly in pre-Gondwana dispersion times