Assembly, configuration, and break-up history of Rodinia: A synthesis

Orogenic gold deposits : A proposed classification in the context of their crustal distribution and relationship to other gold deposit types

/pdf/global-continental-and-ocean-basin-reconstructions-since-200-huopwd2ldv.pdf

Global continental and ocean basin reconstructions since 200 Ma

Adakitic magmas: modern analogues of Archaean granitoids

Review of global 2.1-1.8 Ga orogens: implications for a pre-Rodinia supercontinent

In order to constrain the temporal relationship between granite (sensu lato) emplacement and metamorphism, isotope work was carried out on the minerals zircon and apatite (U–Pb), garnet (Pb–Pb) and hornblende (Ar–Ar) from wall rock samples in the Shamva area in Zimbabwe. The area, encompassing parts of the Chinamora and Murehwa batholiths and a wedge-shaped greenstone belt segment in between, is commonly quoted in the literature as an example illustrating pluton emplacement processes and deformational models for the Archean. New U–Pb dating of apatite from a boudinaged pegmatite within mafic schists in the batholith–greenstone contact zone has yielded an age of 2619 +28/–24 Ma. This age is interpreted as the best estimation of the intrusion age of this unit, depending on the assumed closure temperature, and provides an upper age limit for the syntectonic emplacement of the now gneissic granites. Pb–Pb dating of late kinematic garnets in cordierite-bearing rocks within the greenstone belt wall rocks gives an age of 2623±8 Ma. Together, this timing of relatively late, syntectonic plutonism and metamorphic mineral growth at ca. 2.62 Ga compares well with existing zircon crystallization ages for felsic volcanics (2645±4 Ma, 2643±8 Ma) and post-tectonic porphyritic monzogranites (2601±14 Ma). Ar–Ar hornblende ages for mafic schists from different areas within the greenstone belt wall rocks range between 2621 and 2498 Ma and have been interpreted to indicate mixing between metamorphic ages and cooling ages. The data support a geological model whereby volcanism and sedimentation are associated with an early phase of regional deformation at ca. 2.64 Ga, which may have started earlier and lasted longer, and evolves into the voluminous emplacement of granites (now gneissic granites) in the batholiths at approximately 2.62 Ga. Emplacement of post-tectonic tabular monzogranites takes place at ca. 2.60 Ga.

Constraints on the timing of granite emplacement, deformation and metamorphism in the Shamva area, Zimbabwe

The Quaternary history of effusive volcanism of the Nevado de Toluca area, Central Mexico

Long distance plutonic relationships demonstrate 33 million years of strain partitioning along the Denali fault

Early Miocene arc volcanism in the Mexico City Basin: Inception of the Trans-Mexican Volcanic Belt

This chapter reports new field, petrographic, and geochemical data for two Tertiary volcanic units and underlying sedimentary rocks in the southeast corner of the Mount McKinley 1:250,000-scale quadrangle. The volcanic units include the late Paleocene and early Eocene volcanic rocks of Foraker Glacier and the late Eocene and early Oligocene Mount Galen Volcanics. New 40 Ar/ 39 Ar dating on two samples from the lower part of the volcanic rocks of Foraker Glacier yield ages of 56.9±0.2 and 55.5±0.1 Ma. The volcanic rocks of Foraker Glacier unconformably overlie a 550-m-thick sequence of Late Cretaceous(?) sedimentary rocks that dip steeply north and unconformably overlie Paleozoic metamorphic rocks with a schistosity that dips steeply south. The sedimentary sequence includes a metamorphic-clast cobble-boulder alluvial-fan conglomerate overlain by fluvial and lacustrine conglomerate, sandstone, and mudstone. The coarse grain size and presence of bounding unconformities indicate that these sedimentary rocks fill a contractional basin and record pre-late Paleocene tectonic uplift of the adjacent Paleozoic metamorphic rocks. The overlying volcanic rocks of Foraker Glacier consist of a 200-m-thick interval of basalt and andesite lavas containing interbedded mudstone and volcaniclastic fluvial conglomerate overlain by 1,500 m of rhyolite lava and interbedded pyroclastic-flow deposits. The basalts are slightly depleted in incompatible trace elements (light rare-earth elements, Rb, Th, K) and along with the andesites have high Ba/Ta ratios (464–1,160). The rhyolites are strongly enriched in light rare-earth elements (LREEs), Rb, Th, and K, are depleted in Sr, P, and Ti, and have low Ba/Ta ratios (23–137), all of which indicate a combination of crustal assimilation and fractional crystallization in their petrogenesis. The Mount Galen Volcanics consists of basalt, andesite, dacite, and rhyolite lavas and dacite and rhyolite tuff and tuff-breccia. New 40 Ar/ 39 Ar dating of a basaltic andesite flow

/pdf/stratigraphy-age-and-geochemistry-of-tertiary-volcanic-rocks-2eks6v2u0x.pdf

Paul W. Layer

Papers

Constraints on the timing of granite emplacement, deformation and metamorphism in the Shamva area, Zimbabwe

The Quaternary history of effusive volcanism of the Nevado de Toluca area, Central Mexico

Long distance plutonic relationships demonstrate 33 million years of strain partitioning along the Denali fault

Early Miocene arc volcanism in the Mexico City Basin: Inception of the Trans-Mexican Volcanic Belt

Stratigraphy, Age, and Geochemistry of Tertiary Volcanic Rocks and Associated Synorogenic Deposits, Mount McKinley Quadrangle, Alaska