A Triassic to Cretaceous Sundaland–Pacific subduction margin in West Sarawak, Borneo

Metamorphic rocks in West Sarawak are poorly exposed and studied. They were previously assumed to be pre-Carboniferous basement but had never been dated. New 40Ar/39Ar ages from white mica in quartz-mica schists reveal metamorphism between c. 216 to 220 Ma. The metamorphic rocks are associated with Triassic acid and basic igneous rocks, which indicate widespread magmatism. New U-Pb dating of zircons from the Jagoi Granodiorite indicates Triassic magmatism at c. 208 Ma and c. 240 Ma. U-Pb dating of zircons from volcaniclastic sediments of the Sadong and Kuching Formations confirms contemporaneous volcanism. The magmatic activity is interpreted to represent a Triassic subduction margin in westernmost West Sarawak with sediments deposited in a forearc basin derived from the magmatic arc at the Sundaland–Pacific margin. West Sarawak and NW Kalimantan are underlain by continental crust that was already part of Sundaland or accreted to Sundaland in the Triassic. One metabasite sample, also previously assumed to be pre-Carboniferous basement, yielded Early Cretaceous 40Ar/39Ar ages. They are interpreted to indicate resumption of subduction which led to deposition of volcaniclastic sediments and widespread magmatism. U-Pb ages from detrital zircons in the Cretaceous Pedawan Formation are similar to those from the Schwaner granites of NW Kalimantan, and the Pedawan Formation is interpreted as part of a Cretaceous forearc basin containing material eroded from a magmatic arc that extended from Vietnam to west Borneo. The youngest U-Pb ages from zircons in a tuff layer from the uppermost part of the Pedawan Formation indicate that volcanic activity continued until c. 86 to 88 Ma when subduction terminated

Provenance of the Cretaceous–Eocene Rajang Group submarine fan, Sarawak, Malaysia from light and heavy mineral assemblages and U-Pb zircon geochronology

The Rajang Group sediments in central Borneo form a very thick deep-water sequence which was deposited in one of the world's largest ancient submarine fans. In Sarawak, the Lupar and Belaga Formations form the Rajang Group, characterised by turbidites and large debris flows, deposited in an interval of at least 30Ma between the Late Cretaceous (Maastrichtian) and late Middle Eocene. Borneo is one of the few places in SE Asia where sediments of this age are preserved. Heavy mineral assemblages and detrital zircon U-Pb dating permit the Rajang Group to be divided into three units. The Schwaner Mountains area in SW Borneo, and West Borneo and the Malay Tin Belt were the main source regions and the contribution from these source areas varied with time. Unit 1, of Late Cretaceous to Early Eocene age, is characterised by zircon-tourmaline-dominated heavy mineral assemblages derived from both source areas. Unit 2, of Early to Middle Eocene age, has zircon-dominated heavy mineral assemblages, abundant Cretaceous zircons and few Precambrian zircons derived primarily from the Schwaner Mountains. Unit 3, of Middle Eocene age, has zircon-tourmaline-dominated heavy mineral assemblages derived from both sources and reworked sedimentary rocks. There was limited contemporaneous magmatism during deposition of the Rajang Group inconsistent with a subduction arc setting. We suggest the Rajang Group was deposited north of the shelf edge formed by the Lupar Line which was a significant strikeslip fault

Evaporation-driven thermocapillary Marangoni convection in liquid layers of different depths

In the experimental part, which employed infrared (IR) camera, temperature distributions at the free surface of ethanol layers in deep and shallow vessels under room temperature or subjected to heating from below in the 68 °C - 105 °C temperature range (including the ethanol boiling temperature of 78.3 °C) were studied, and correlated with the heater surface temperature. The regular and irregular Marangoni convection patterns were recognized. Light particles fully entrained by the Marangoni convection on the free surface were tracked and their velocities were measured and compared to the theoretical predictions. Namely, a model is developed for the Marangoni-driven convection due to a non-uniform evaporationrelated cooling of the free surface of a liquid in anopen vessel. In this case, an analytical solution