Figure 1:
Geologic map of the Ischigualasto-Villa Union Basin. Modified from Caselli (2000Caselli A.T. (2000). Estudio sedimentológico de las formaciones Talampaya y Tarjados (Triássico Inferior) en el flanco occidental de la Sierra de Sanõgasta, provincia de La Rioja (Argentina). In: 6 Reunión Sobre el Triásico Del Cono Sur, San Luis.).
Figure 2:
Field and microscopic features of the Cerro Morado (cf. Alexandre et al. 2009Alexandre F.P., Sommer C.A., Lima E.F., Chemale Jr. F., Marsicano C.A., Mancuso A.C., Brod J.A. (2009). Petrologia do magmatismo básico do Cerro Morado na bacia triássica Ischigualasto-Villa Unión (NW da Argentina). Pesquisas em Geociências, 36:295-313.). (A) Front view of the Cerro Morado, including the contact relationship between the two units; (B) olivine euedric phenocryst embedded in fine-grained matrix of the diabase; (C) plagioclase phenocryst of the diabase; (D) subophitic texture in diabase; (E) imbricated plagioclase crystals in the matrix of the tephrite; (F) augite phenocryst with rims altered to chlorite and iron; (G) analcite phenocryst with anedric habit immersed in matrix with branching texture; (H) vesicle filled by carbonate.
Figure 3:
Geochemical diagram of characterization of the Cerro Morado rocks (cf. Alexandre et al. 2009Alexandre F.P., Sommer C.A., Lima E.F., Chemale Jr. F., Marsicano C.A., Mancuso A.C., Brod J.A. (2009). Petrologia do magmatismo básico do Cerro Morado na bacia triássica Ischigualasto-Villa Unión (NW da Argentina). Pesquisas em Geociências, 36:295-313.). Nb/Y vs Zr/TiO2*0.0001 diagram (Winchester & Floyd 1977Winchester J.A., Floyd P.A. (1977). Geochemical discrimination of different magma series and their differentiation products using immobile elements. Chemical Geology, 20:325-343.) where the samples occupy the alkali basalt field.
Figure 4:
Major and minor element variation diagrams versus differentiation index (DI) for the Cerro Morado rocks (cf. Alexandre et al. 2009Alexandre F.P., Sommer C.A., Lima E.F., Chemale Jr. F., Marsicano C.A., Mancuso A.C., Brod J.A. (2009). Petrologia do magmatismo básico do Cerro Morado na bacia triássica Ischigualasto-Villa Unión (NW da Argentina). Pesquisas em Geociências, 36:295-313.).
Figure 5:
Trace element variation diagrams versus differentiation index (DI) for the Cerro Morado rocks (cf. Alexandre et al. 2009Alexandre F.P., Sommer C.A., Lima E.F., Chemale Jr. F., Marsicano C.A., Mancuso A.C., Brod J.A. (2009). Petrologia do magmatismo básico do Cerro Morado na bacia triássica Ischigualasto-Villa Unión (NW da Argentina). Pesquisas em Geociências, 36:295-313.).
Figure 6:
Multielementary diagram of the Cerro Morado rocks (cf. Alexandre et al. 2009Alexandre F.P., Sommer C.A., Lima E.F., Chemale Jr. F., Marsicano C.A., Mancuso A.C., Brod J.A. (2009). Petrologia do magmatismo básico do Cerro Morado na bacia triássica Ischigualasto-Villa Unión (NW da Argentina). Pesquisas em Geociências, 36:295-313.). (A) Distribution of the trace elements normalized to OIB (Sun & McDonough 1989Sun S.S., McDonough W.F. (1989). Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes. In: Saunders A.D., Norry M.J. (eds.), Magmatism in ocean basins, London, Geological Society of London Special Publication, v. 42, p. 313-345.); (B) rare earth elements diagram normalized to chondrites (Nakamura 1974Nakamura N. (1974). Determination of REE, Ba, Fe, Mg, Na and K in carbonaceous and ordinary chondrites. Geochimica et Cosmochimica Acta, 38:757-775.).
Figure 7:
Cerro Morado samples plotted in diagrams of tectonic environment (cf. Alexandre et al. 2009Alexandre F.P., Sommer C.A., Lima E.F., Chemale Jr. F., Marsicano C.A., Mancuso A.C., Brod J.A. (2009). Petrologia do magmatismo básico do Cerro Morado na bacia triássica Ischigualasto-Villa Unión (NW da Argentina). Pesquisas em Geociências, 36:295-313.). (A) Zr/4-Y-Nbx2 diagram (Meschede 1986Meschede M. (1986). A method of discrimination between different types of mid-ocean ridge basalts and continental tholeiites with the Nb-Zr-Y diagram. Chemical Geology, 56:207-218.); (B) Th-Hf/3-Nb diagram (Wood 1980Wood D.A. (1980). The application of a Th-Hf-Ta diagram to problems of tectonomagmatic classification and to establishing the nature of crustal contamination of basaltic lavas of the British Tertiary Volcanic Province. Earth and Planetary Science Letters, 50:11-30.); (C) Zr-Zr/Y diagram (Pearce & Cann 1973Pearce J.A., Cann J.R. (1973). Tectonic setting of basic volcanic rocks determined by using trace element analyses. Earth and Planetary Science Letters, 19:290-300.); (D) Th/Yb versus Ta/Yb diagram showing the samples plot between the OIB and E-MORB signatures (Pearce 1983Pearce J.A. (1983). Role of the sub-continental lithosphere in magma genesis at active continental margins. In: Hawkesworth C.J., Norry M.J. (eds.), Continental Basalts and Mantle Xenoliths. Nantwich, Shiva Publications, p. 230-249.).
Figure 8:
143Nd/144Ndi versus 87Sr/86Sri variation diagram for the studied hypabissais rocks. The mantle components DM, PREMA, HIMU, EM-I, and EM-II are taken from Zindler and Hart (1986Zindler A., Hart S. (1986). Chemical geodynamics. Annual Review of Earth and Planetary Sciences, 14:493-571.). The mantle reservoir fields are those recalculated at 200 Ma by Deckart et al. (2005Deckart K., Bertrand H., Liégois J.P. (2005). Geochemistry and Sr, Nd, Pb isotopic composition of the Central Atlantic Magmatic Province (CAMP) in Guyana and Guinea. Lithos, 82:289-314.), close to the approximate crystallization age estimated for the Cerro Morado around 228 Ma. The mantle array position was recalculated at 285 Ma by Vozár et al. (2015Vozár J., Spisiak J., Vozárová A., Bazarnik J., Král J. (2015). Geochemistry and Sr, Nd isotopic composition of the Hronic Upper Paleozoic basic rocks (Western Carpathians, Slovakia). Geologica Carpathica, 66:3-17.), also close to the crystallization age of the Cerro Morado.
Figure 9:
Lead isotope compositions for the studied rocks in comparison to mantle components PREMA, EM-I, EM-II, and DM (Zindler & Hart 1986Zindler A., Hart S. (1986). Chemical geodynamics. Annual Review of Earth and Planetary Sciences, 14:493-571.). NHRL, Northern Hemisphere Reference Line (Hart 1984Hart S.R. (1984). A large-scale isotope anomaly in the southern hemisphere mantle. Nature, 309:753-757.). The reservoirs fields are present-day Pb ratios.
Figure 10:
87Sr/86Sri and 143Nd/144Ndi against present-day Pb isotope compositions for the studied rocks compared to the fields of the mantle components HIMU, PREMA, EM-I, EM-II and DM (Zindler & Hart 1986Zindler A., Hart S. (1986). Chemical geodynamics. Annual Review of Earth and Planetary Sciences, 14:493-571.).
Figure 11:
Diagrams indicative of crustal contamination. (A) Ba/Yb versus 87Sr/86Sri plot. The vectors are from Wilson (1989Wilson M. (1989). Igneous Petrogenesis: a global tectonic approach. London, Springer.) and refer to open-system fractional crystallization (AFC) and closed-system fractional crystallization (FC); (B) plot of initial Sr isotope ratios versus SiO2 (wt.%); (C) plot of initial Sr isotope ratios versus P2O5/K2O .
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