Sapphirine-bearing rocks with sedimentary and volcanogenic protoliths from the Arunta Block
AT least 15 separate localities for sapphirine-bearing rocks have been found in the Arunta Block, a Precambrian metamorphic complex in central Australia (Fig. 1), although only two have been documented in any detail1–3. Such rocks are the most spectacular examples of a suite of rocks with a distinctive, characteristic chemistry. This suite includes, inter alia, the better known cordierite–anthophyllite rocks, and is widely distributed both within the Arunta Block and world-wide. From field observations it is proposed here that two different geological processes, one sedimentary or diagenetic and the other volcanic, generated rocks that are now indistinguishable in their whole-rock chemistry and mineral assemblages. It had formerly been proposed that sapphirine-bearing rocks of volcanogenic and sedimentary origins were mineralogically and chemically distinct4.
Field relations and chemistry of sapphirine-bearing rocks from the Bjoresund area, Fiskenaesset, western Greenland
Two contrasting sapphirine-bearing assemblages are described: a higbly maguesian one, developed sporadically at the upper contact of the FisketrEsset Complex in association with layered ultramafic rocks, and the other, more iron-rich, in the amphibolite bordering the Complex. Mineral assemblages described are oftwo kincls: (1) iron-poor: enstatite phlogopite olivine pargasite sapphirine spinel, gedrite sapphirine spinel, and enstatite gedrite phlogopite sapphirine spi4el; (2) iron-rich: magnesiohornblende sapphirine spinel anorthite. Only the ironpoor sapphirine-bearing assemblages and their associates are characterized by the presence of accessory apatite, rutile and zircon, which may indicate a possible sedimentary origin for at least some of the sapphirine-bearing material. The iron-rich assemblage is found within rocks considered to be entirely of igneous origin.
The Inca Occupation of the South Coast of Peru
like the others, however; it forks into several nearly parallel ravines of which the largest are Huayuri, Rio Grande-Palpa, Ingenio (called Collao in ancient times), Nasca proper (the ancient Caxamarca), Taruga, and Poroma. Due to peculiarities of the local topography, the irrigated areas in Ica and the ravines of Nasca are located inland, at the foot of the mountains, rather than at the mouths of the rivers as is more usual in Peruvian coastal valleys. No sharp natural or cultural boundary separates the valley of Chincha from the valleys of Cafiete (ancient Huarco and Runahuana), Asia, and Mala, the next valleys going up the coast to the northwest. At the other end of the area we are considering, however, there is a sharp break; beyond Yauca the Andean foothills reach out to the sea, natural conditions are quite different, and there are important differences in the archaeological picture as well. The historical sources which mention the south coast are not particularly helpful, except in so far as they provide us with a few dates. To begin with, no chronicler gives an explicit account of the political organization of the south coast at the time it came into contact with the Incas. It can, perhaps, be inferred from Cabello Balboa's statements about common policy toward the Inca invaders that there was some sort of political connection between the valleys of Mala, Cafiete, and Chincha, but the connection need have been no more than a temporary military alliance. Cabello makes no mention at all of Pisco. The valleys of Ica, Nasca, and 125