Description: Scandium is important in modern technology and is regarded as a strategic metal in many countries. It is highly dispersed in Earth’s crust and rarely forms independent minerals. Clinopyroxene is the most important Sc-bearing mineral in some world-class deposits hosted in mafic–ultramafic intrusions, which are also the major source of laterite-hosted Sc deposits. However, the factors controlling Sc distribution in minerals have been little explored, impeding the understanding of the geochemical behavior of Sc and why it is common in some clinopyroxene grains. The newly discovered Mouding Sc deposit in SW China is hosted in a zoned intrusion composed, from core to rim, of monzogabbro, syenogabbro, gabbro, magnetite clinopyroxenite, and clinopyroxenite. Clinopyroxene in the intrusion is diopsidic in composition with high Sc contents (80–105 ppm). In-situ trace element mappings of diopside crystals reveal homogeneous, zoned, swallow-tailed, and hourglass internal Sc distribution patterns. These patterns can be produced through kinetically controlled incorporation of Sc on different crystal faces. The preferential substitution of Sc can take place on the {1 0 0}, {1 1 0} and {0 1 0} prism faces because of the high flexibility of the octahedral M1 protosites. The fast growth of diopside, which facilitates kinetically controlled crystallization, is dominated by textural coarsening and promoted by the hydrous parental magmas with low viscosities and active convection. The active flow and efficient interstitial communication of the magma can direct compatible elements from the magma into clinopyroxene, thus favoring formation of Sc-rich grains. Our study provides a feasible way to study intra-grain variations of Sc in minerals and emphasizes that kinetic effects may play a critical role in Sc distribution and enrichment in hydrous magmatic Sc deposits. We also show that disequilibrium crystallization may be more pervasive than previously thought, and the hourglass zoning of clinopyroxene can provide valuable information on this process.

Description: The spatial and angular emission patterns of artificial and natural light emitted, scattered, and reflected from the Earth at night are far more complex than those for scattered and reflected solar radiation during daytime. In this commentary, we use examples to show that there is additional information contained in the angular distribution of emitted light. We argue that this information could be used to improve existing remote sensing retrievals based on night lights, and in some cases could make entirely new remote sensing analyses possible. This work will be challenging, so we hope this article will encourage researchers and funding agencies to pursue further study of how multi-angle views can be analyzed or acquired.

Description: Constraining the Cenozoic uplift of Tian Shan is important for assessing the impact of the India-Asia collision to Central Asia. Here we estimate the uplift history of the Bogda Shan, northeastern Tian Shan, using a thermo-kinematic model which is constrained by previously reported apatite fission-track thermochronological data. By assuming that the growth of the mountain range propagates towards the basin as a classic critical wedge model, we show that the observed variation in the cooling ages on the mountain flank can be used to provide constraints on the timing and rate of the deformation along a series of south dipping thrust faults, which all root on a low-angle décollement. Inverse modeling confirms previous findings from thermal history models that the Cenozoic uplift in the Bogda Shan initiated during the Paleogene, no later than ~40 Ma. Since the early Miocene (~23 Ma), locus of uplift has expanded to the current southern margin of the Junggar Basin. Our kinematic model of the deformation of the Bogda Shan suggests a temporal stability in the shortening rate of the northeastern Tian Shan over the period of the India-Asia collision during the late Cenozoic.