Cautions for the estimation of equivalent current systems from geomagnetic data

Spherical harmonic geomagnetic data analysis is a convenient technique to estimate equivalent current systems and to separate the external from the internal fields. However, there are certain cautions which need to be taken in the procedure, as demonstrated by some examples of the analyses of geomagnetic daily variations during solar active and quiet periods. Questions concerning the proper level of series truncation, problems with sharp gradients of the northward amplitude in narrow latitudinal zones, and dependence of results on which horizontal component is selected (northward, eastward or both) are discussed for the northern hemispheric equivalent current systems.     

Land suitability analysis for maize production in Indonesia using satellite remote sensing and GIS-based multicriteria decision support system

GeoJournal - Maize is one of the potential crops can help in regional food production with self-sufficiency of foods in the drought prone areas of East Java in Indonesia. The purpose of this...     

Crustal anatexis and formation of two types of granitic magmas in the Kontum massif, central Vietnam: Implications for magma processes in collision zones

Asia grew in the Late Permian by the collision of a number of micro-continents. Syn- to post-collisional magmatism occurred along the continental collision zones . In this study, we report two types of granitic rocks, garnet granite (Grt granite) and orthopyroxene granite (Opx granite), from the Kontum massif, central Vietnam, which is situated on the continental collision zone between the South China and Indochina cratons. These granitic rocks were formed at ca. 250 Ma when high-temperature (HT) and ultrahigh-temperature (UHT) metamorphism took place in the same zone. Based on the petrological and geochemical features compared with previously reported experimental results, garnet-bearing granite is derived from pelitic gneisses by partial melting, whereas orthopyroxene-bearing granite is produced by the partial melting of garnet-bearing mafic granulites. We inferred that a significantly high-geothermal gradient is required to produce Vietnamese granitic magmatism and related HT to UHT metamorphism. This geotherm may be attributed to upwelling mantle plume beneath the Kontum massif during the Late Permian.