The author wishes to clarify the equation that was used in the ‘Early amphibole crystallization in adakitic and associated melts’ subsection of the Discussion section of the published version of this paper. The corrected paragraph containing the equation should read as follows:
Amphiboles probably record the compositional variations of their equilibrium melt on its liquid line of descent. In particular, the Fe/Mg ratio of the amphiboles positively correlates with the Fe/Mg ratio of their parental melt during its differentiation (
Alonso-Perez et al. , 2009), suggesting that they capture the Fe–Mg compositional heterogeneities of their equilibrium melt. For instance, experimental amphiboles in equilibrium with primitive basaltic melts have high Mg# (0·83–0·75;
Grove et al., 2003) in comparison to amphibole in equilibrium with evolved, residual andesites (Mg# ≤ 0·65;
Alonso-Perez et al., 2009). Amphiboles from Baja California and the Philippines have average Mg# in the range of 0·67–0·80 and 0·57–0·81, respectively. Their Mg-numbers (Mg#) mostly overlap the compositional range of the amphiboles in equilibrium with the primitive melts, suggesting that amphiboles are early fractionation products of water-saturated mantle melts (
Hidalgo & Rooney, 2010;
Rooney et al., 2011). Lower Mg# in the amphiboles may reflect variations in the pre-eruptive magma storage conditions (i.e.
f O
2,
P,
T,
fH
2O) or crystallization from evolved andesitic melts. Therefore, to establish if the Philippines and Baja California amphiboles crystallized from primitive arc melts, we estimated the degree of differentiation of their parental melt by calculating their Mg# using the equation
(
KDFe/Mg = 0·38 ± 0·04;
Alonso-Perez et al., 2009). Primitive melts that formed by partial melting of the asthenospheric mantle have Mg# > 0·65, whereas differentiated melts have much lower Mg# (<0·60;
Grove et al., 2003,
2012). The decrease in Mg# as the melt differentiates results from the early crystallization of Mg-rich mineral phases (e.g. olivine) that partition MgO relative to FeO (
Grove et al., 2003,
2012). Melts in equilibrium with the Baja California and Philippines amphiboles have average Mg# > 0.65 (
Supplementary Data Electronic Appendices 1 and 2), suggesting that these amphiboles represent early phases that crystallized from water-rich, primitive arc melts.
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