The end-Triassic extinction is one of the Phanerozoic's largest mass extinctions. This extinction is typically attributed to climate change associated with degassing of basalt flows from the central Atlantic magmatic province (CAMP). However, recent work suggests that the earliest known CAMP basalts occur above the extinction horizon and that climatic and biotic changes began before the earlies...

Significant magnetite, in the form of dyke-like lodes (Cockfield. 1948). occurs in close spatial relationship to copper deposits such as the Afton mine. The genetic relationship of these massive magnetite lodes to the copper deposits of the Iron Mask is unknown, as i s the origin of the magnetite deposits. However, the proximity of these deposits to magnetite-rich intrusive units of the Iron Ma...

Meteoritic chondrules are submillimeter spherules representing the major constituent of nondifferentiated planetesimals formed in the solar protoplanetary disk. The link between the dynamics of the disk and the origin of chondrules remains enigmatic. Collisions between planetesimals formed at different heliocentric distances were frequent early in the evolution of the disk. We show that the pre...

Using a recent compilation of African alkaline igneous rocks and carbonatites, we show that nearly 90% (28 of 32 occurrences) of nepheline syenite gneisses and deformed carbonatites are concentrated within known or inferred Proterozoic suture zones. Given the wellestablished intracontinental rift setting for these rocks and the likely continental collisional setting for their subsequent deforma...

Mantle oxygen fugacity exerts a primary control on mass exchange between Earth's surface and interior at subduction zones, but the major factors controlling mantle oxygen fugacity (such as volatiles and phase assemblages) and how tectonic cycles drive its secular evolution are still debated. We present integrated measurements of redox-sensitive ratios of oxidized iron to total iron (Fe3+/SigmaF...

The Ok Tedi Complex hosts a world-class porphyry copper-gold deposit. Samples from the Ok Tedi Complex and the neighbouring Mount Ian Complex were analyzed for major and trace elements using XRF and HR-ICP-MS, and the isotopic composition of S in sulphides was analyzed by Elemental Analyzer. Major element geochemistry indicates that both complexes are alkaline and contain rocks ranging in compo...

Geochronologic dating and compilation of existing age data suggest that Cenozoic activities in the eastern Indo^ Asian collision zone of southeast China and Indochina occurred in two episodes, each with distinctive geochemical signatures, at 42^24 Myr and 16^0 Myr. The older rocks are localized along major strike^slip faults such as the Red River fault system and erupted synchronously with tran...

Clay minerals may be si<j'nifieant indieatoi's of earth processes. They form throufrh a range which involves at one extreme the action of compressed water vapor at a temperature of several hundred degrees centigrade, and at the other extreme, the action of atmospheric agencies at an ordinary temperature. Not recognized as original products of magmatic crystallization, clay minerals are prima fa...