Magmatism in the Asunción-Sapucai-Villarrica Graben (Eastern Paraguay) Revisited: Petrological, Geophysical, Geochemical, and Geodynamic Inferences
Figure 8
Calculated subcontinental upper mantle (SCUM) isotopic composition at 2.0 Ga ago, projected to 130 Ma [85], modified after Figure 10 of [6]. Parental melts with various Rb/Sr and Sm/Nd ratios are assumed for K, Na (potassic and sodic rocks from ASV [10]), and PAE tholeiites [3]. It should be noted that the compositions of metasomites formed from a single metasomatizing melt vary with the evolution of the melt. Consequently, the veins will define a trend of shallow slope, and mixing curves between vein and matrix will define an array towards the matrix (cf. α and β regression lines). Model depleted mantle (DMM): Rb = 0, Sr = 0.133, Sm = 0.314, and Nd = 0.628; present day Bulk Earth: 87Sr/86Sr = 0.70475, 87Rb/86Sr = 0.0816, 143Nd/144Nd = 0.512638, and 147Sm/143Nd = 0.1967; : ≈ 0.125, : ≈ 1.5; K : Rb/Sr = 0.0957, Sm/Nd = 0.1344; Na : Rb/Sr = 0.0732, Sm/Nd = 0.2295; Th : Rb/Sr = 0.0733, Sm/Nd = 0.2082.
