Explore the vast range of titles available.

Most of the sills described so far in this chapter [Palisades, Shiant, Dillsburg, Elephant's Head dyke, Black Jack, Tasmanian dolerites, Ferrar dolerites] can be said to exhibit certain features in common. They are sills in which crystal settling has probably taken place, although in most cases this is confined to the earliest stages of crystallization and involves minerals, usually olivine, present in the magma at the time of emplacement.

Most of the sills described so far in this chapter [Palisades, Shiant, Dillsburg, Elephant's Head dyke, Black Jack, Tasmanian dolerites, Ferrar dolerites] can be said to exhibit certain features in common. They are sills in which crystal settling has probably taken place, although in most cases this is confined to the earliest stages of crystallization and involves minerals, usually olivine, present in the magma at the time of emplacement.

Most of the sills described so far in this chapter [Palisades, Shiant, Dillsburg, Elephant's Head dyke, Black Jack, Tasmanian dolerites, Ferrar dolerites] can be said to exhibit certain features in common. They are sills in which crystal settling has probably taken place, although in most cases this is confined to the earliest stages of crystallization and involves minerals, usually olivine, present in the magma at the time of emplacement. Wager and Brown (1967).

Most of the sills described so far in this chapter [Palisades, Shiant, Dillsburg, Elephant's Head dyke, Black Jack, Tasmanian dolerites, Ferrar dolerites] can be said to exhibit certain features in common. They are sills in which crystal settling has probably taken place, although in most cases this is confined to the earliest stages of crystallization and involves minerals, usually olivine, present in the magma at the time of emplacement.

Marsh (Contrib Miner Petrol 166:665-690, 2013) again claims that crystal-free basalt magmas are unable to differentiate in crustal magma chambers and regards layered intrusions as primarily due to the repeated emplacement of crystal suspensions. He ignores an earlier critique of his unconventional inferences (Latypov, J Petrol 50:1047-1069, 2009) as well as a wealth of petrographic, geochemical and experimental evidence supporting the dominant role of fractional crystallization in the solidification of layered intrusions. Most tellingly, the cryptic variations preserved in the Skaergaard and many other basaltic layered intrusions would require an exceedingly implausible sequence of phenocrystic magmas but are wholly consistent with in situ fractional crystallization. A major flaw in Marsh's hypothesis is that it dismisses progressive fractional crystallization within any magma chamber and hence prohibits the formation of crystal slurries with phenocrysts and melts that change systematically in composition in any feeder system. This inherent attribute of the hypothesis excludes the formation of layered intrusions anywhere.

The solubility of [H.sub.2]O--C[O.sub.2]--Cl-containing fluids of various concentrations (0, 3, 10, and 23 wt % of HCl and from 0 to ~8--15 wt % of C[O.sub.2]) in dacite, phonolite, and rhyolite melts at 1000[degrees]C and 200 MPa was studied in experiments. It was shown that the Cl concentration in the melt increased substantially from rhyolite to phonolite and dacite (up to 0.25, 0.85, and 1.2 wt %, respectively). The introduction of C[O.sub.2] into the system resulted in an increase in the Cl content in the melt composition by 20-25%. One may suppose that Cl reactivity in a fluid increases in the presence of C[O.sub.2] to cause growth of the Cl content in the melt. The introduction of C[O.sub.2] into the system considerably affects the content of [H.sub.2]O in aluminosilicate melts as well. Thus, the addition of C[O.sub.2] decreases the [H.sub.2]O content in the melt by ~0.5-1.0 wt %. The decrease in the [H.sub.2]O content in an aluminosilicate melt is probably caused by fluid dilution with C[O.sub.2] resulting in a decrease in the [H.sub.2]O mole fraction and fugacity in the fluid.

The essential sources and processes required for the formation of Cu–(Au)-porphyry deposits have been part of a long-standing debate. In this study we investigate one of the youngest and best-preserved world-class Cu–(Au)-porphyry systems in order to learn more about melt sources and what geochemical tracers in zircon and apatite might be useful to identify ore-forming intrusions within porphyry systems. Combined, in-situ Hf, O, and Nd isotope analyses in zircon and apatite imply that the Tampakan magmas were derived from depleted mantle sources. Hence, we suggest that older crustal components or metasomatized mantle are not required for the production of metallogenically fertile magmas in island arc settings. Based on the compositions of apatite and zircon, we confirm that previously established fertility-indicator signatures of these minerals are useful to identify fertile porphyry systems. Our data show that intrusions directly associated with mineralization events contain apatite with elevated Cl and S concentrations compared to pre- and post- mineralization igneous events.

Understanding the primary controls on mineral deposit formation and size is essential for sourcing the metals required by our ever-growing economy. The tonnage of porphyry copper deposits ranges five orders of magnitude but the key mechanisms and processes that modulate the size of these deposits remain enigmatic. Here, we investigate the behemothian deposits of the Chuquicamata Intrusive Complex (CIC) in northern Chile employing high-precision U–Pb and Re–Os geochronology. We resolve a complex long-lived magmatic-hydrothermal activity that lasted over 3.3 Myr. High-precision zircon petrochronology data indicate two distinct porphyry emplacement episodes, separated by 0.5 Myr, with the younger generation closely tied to the main intervals of hydrothermal mineralization. High-precision Re–Os molybdenite dates reveal a prolonged hydrothermal mineralization interval (> 2.5 Myr) that progressively migrated southwards within the CIC and continued after the end of the (apparent) magmatic activity. We show that the rate of copper precipitation varies little in nature (0.025–0.10 Mt/kyr) and is independent of the size of the deposit. Consistent with evidence from smaller deposits, our findings provide unprecedented evidence that copper endowment in porphyry copper deposits positively correlates with the timescales of magmatic and hydrothermal activity. Supergiant to behemothian deposits require multi-million-year magmatic-hydrothermal activity, linking the largest porphyry copper systems to a simple metric – the duration of magmatic-hydrothermal activity.