作者: J.D. Clemens , W.D. Birch
DOI: 10.1016/J.LITHOS.2012.09.007
关键词: Volcano 、 Rhyolite 、 Protolith 、 Igneous rock 、 Geology 、 Caldera 、 Geochemistry 、 Magma 、 Magma chamber 、 Volcanic rock
摘要: Abstract The Late Devonian (374 Ma) Cerberean Cauldron forms the northern part of Marysville Igneous Complex, in Central Victoria, Australia, filled with around 900 km 3 intra-caldera ignimbrites. basal volcanic formation is rhyolitic high-Al Rubicon Ignimbrite, overlain by a larger volume crystal-rich low-Al which grades upward into voluminous, rhyodacitic Lake Mountain Ignimbrite. rocks are S-type character, initial 87 Sr/ 86 Sr 0.709 to 0.710 and eNd t varying from − 4.7 − 6.0, suggesting metagreywacke protoliths. chemistry incompatible differentiation mechanism. Experimentally determined phase relations Ignimbrite show that early crystallisation magma began at > 450 MPa > 875 °C (possibly up 940 °C), an H 2 O content 4.1 5.3 wt.%. In pre-eruption chamber, had temperature ≥ 780 °C contained ≥ 4 wt.% O. Each formation, indeed smaller volumes rock, appears have been produced partial melting slightly contrasting greywackes protolith spatial variations its mineralogy, delivered batches high-level chamber. magmas underwent some internal differentiation, probably crystal settling, prior eruption, most due small but variable degrees peritectic entrainment. limited gradation between minor, mixing across interface. Such individual typical anatectic granitic magmas.