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The time and rate of Tibetan uplift is critical in understanding both the geodynamics of plateau growth and the influence of mountain building on climate change. Models predict that the uplift of the north Tibetan Plateau (NTP) occurred later than uplift of the south and central Tibetan Plateau; uplift of the NTP is believed to have initiated the aridity in the interior of Asia, and to have critically affected the evolution of Asian monsoon and, ultimately, global climate. The history of NTP uplift has remained uncertain, however; scenarios range from Early Miocene to the past million years. This work provides new evidence by relating the Nd isotopic evolution of Asian dust to NTP uplift. The sources of the Asian dust are located in the arid lands between the NTP and the Central Asia orogen. Mass balance calculations indicate that the decreasing e Nd values, from −8.2 to −10.4 for Pacific dust since 15 Ma, reflects increasing relative contribution of NTP materials (40% to 70%) to the dust source. As paleoelevation in the Central Asia orogen has largely remained constant, the increasing relative NTP detritus contribution is interpreted to reflect the progressive surface uplift of the NTP at a rate of at least 0.12 mm yr −1 since 15 Ma.

The ultradeep mantle rocks of western Norway display three generations of majoritic garnet. The first two derive from incompatible element–depleted transition-zone mantle and exsolved pyroxene components during Archean upwelling, accretion to subcratonic lithosphere (M1 stage), and isobaric cooling until the Middle Proterozoic (M2). A subsequent Scandian (430–390 Ma) subduction cycle initiated diamond crystallization (M3). Here we report a third majoritic garnet crystallized at grain boundaries and in microfractures, and stable with pyroxene, phlogopite, and spinel in the M3 assemblage. The trace element signatures of M3 minerals indicate crustal metasomatism, phlogopite being the main large ion lithophile element repository. These features imply majorite crystallization from crust-derived subduction fluids at 200 km depth. Our finding fixes the deepest occurrence of free subduction fluid phases and indicates that garnet is a reliable monitor of deep mantle evolution and fluid-mediated chemical recycling.

The profound glaciations of the Neoproterozoic Cryogenian period (ca. 850–544 Ma) represent an extreme climatic mode when, it is claimed, Earth was fully or almost completely covered with ice for millions of years. We show that the geochemistry and mineralogy of fine-grained Neoproterozoic sedimentary rocks in Oman are best explained by climatic oscillations that drove variations in the intensity of chemical weathering on contemporary land surfaces. The cold climate modes of the Cryogenian were therefore cyclical, punctuated with well-defined warm-humid interglacial periods. The hydrological cycle and the routing of sediment were active throughout the glacial epoch, which requires substantial open ocean water. This reconstruction represents a significantly different target for numerical climate models at this critical time in the evolution of Earth's biosphere.

A long-standing debate surrounds the source of hydrothermal fluids that form gold lodes late in the metamorphic history of orogenic belts. 40 Ar/ 39 Ar dating of hydrothermal muscovite shows that gold lodes in the northwestern Alps formed from 31.6 to 10.6 Ma. The deposits young progressively along the orogen, parallel to field gradients showing decreasing age of peak metamorphism, increasing metamorphic grade, and increasing extent of exhumation of the host rocks. These correlations suggest that the ore-bearing fluid was produced by a 20 m.y. history of prograde metamorphic devolatilization of calc-schists at depth. The age trend of mineralization reflects continuous ascent of fluid and vein formation in retrograding rocks during extreme differential uplift and denudation of the Alpine orogenic wedge. The intimate correlations between collisional orogenesis, metamorphism, and gold mineralization in the Alps suggest that similar genetic scenarios may apply to late orogenic gold lodes elsewhere.