A preliminary case study of potential ceramic raw materials in the Aileu area of Timor Leste

The newly independent country of Timor Leste is located in the eastern half of Timor Island (Indonesian archipelago). Geological studies of the country’s mineral resources and extractive activities are practically non-existent. There is evidence of the exploitation of ceramic raw materials at outcrop level and two small brick kilns, nowadays inactive, in the Dili and Aileu areas. Near Aileu, there are light-coloured silt-rich deposits, interpreted as overbank deposits, interbedded with ancient river terraces (post-Pliocene) overlying metamorphic bedrock. These sediments are the subject of this study, which encompassed geological mapping and preliminary characterisation. Tectonically, the area is a graben, preserving alluvium and colluvium deposits. Five channel samples representative of the silt-rich deposits were collected. Semi-quantitative mineralogical analysis shows that the samples are made of illite, quartz and kaolinite clays, with accessory illite/vermiculite interstratified minerals and K-feldspar. The chemical data show agreement with the estimated mineralogical composition. The grain size distribution points to a silt-dominated assemblage. Most samples have a satisfactory extrudability but deficient moulding properties. After firing, the sampled raw materials form a final product with possible ceramic capability for whiteware production.     

澳大利亚的第三纪及第三纪—第四纪过渡期(英文)

第三纪的板块运动驱动着澳大利亚的气候和植被进行演化。广布的湿润森林区是澳大利亚老第三纪的特征。一直到始新世 ,生物多样性都在不断地提高。毫无疑问 ,这是澳大利亚由高南纬区向北部中纬区运移的结果。从始新世到上新世 ,澳大利亚的气候总体上要比现在湿润 ,但降水量季节性变化的增强推动了中新世以后硬叶植物和旱生植物的发展。上新世晚期似乎与第四纪一样 ,都出现过周期性干旱。这种干旱与冰期条件有关 ,至少由南澳大利亚晚第四纪的记录可以认识到这一点 ,澳大利亚的这段历史与东亚的气候变迁是同步发生的。在东亚 ,印—澳板块的运动致使青藏高原抬升 ,从而引发了区内乃至全球气候的巨变。穿越赤道区的季风和信风的环流格局 ,致使新第三纪和第四纪中国与澳大利亚的气候系统的相关性更强。     

Proterozoic–Paleozoic development of the basement of the Central Andes (18–26°S) — a mobile belt of the South American craton

The Late Precambrian–Early Paleozoic metamorphic basement forms a volumetrically important part of the Andean crust. We investigated its evolution in order to subdivide the area between 18 and 26°S into crustal domains by means of petrological and age data (Sm–Nd isochrons, K–Ar). The metamorphic crystallization ages and t_DM ages are not consistent with growth of the Pacific margin north of the Argentine Precordillera by accretion of exotic terranes, but favor a model of a mobile belt of the Pampean Cycle. Peak metamorphic conditions in all scattered outcrop areas between 18 and 26°S are similar and reached the upper amphibolite facies conditions indicated by mineral paragensis and the occurrence of migmatite. Sm–Nd mineral isochrons yielded 525±10, 505±6 and 509±1 Ma for the Chilean Coast Range, the Chilean Precordillera and the Argentine Puna, and 442±9 and 412±18 Ma for the Sierras Pampeanas. Conventional K–Ar cooling age data of amphibole and mica cluster around 400 Ma, but are frequently reset by Late Paleozoic and Jurassic magmatism. Final exhumation of the Early Paleozoic orogen is confirmed by Devonian erosional unconformities. Sm–Nd depleted mantle model ages of felsic rocks from the metamorphic basement range from 1.4 to 2.2 Ga, in northern Chile the average is 1.65±0.16 Ga (1σ; n=12), average t_DM of both gneiss and metabasite in NW Argentina is 1.76±0.4 Ga (1σ; n=22), and the isotopic composition excludes major addition of juvenile mantle derived material during the Early Paleozoic metamorphic and magmatic cycle. These new data indicate a largely similar development of the metamorphic basement south of the Arequipa Massif at 18°S and north of the Argentine Precordillera at 28°S. Variations of metamorphic grade and of ages of peak metamorphism are of local importance. The protolith was derived from Early to Middle Proterozoic cratonic areas, similar to the Proterozoic rocks from the Arequipa Massif, which had undergone Grenvillian metamorphism at ca. 1.0 Ga.     

An 40Ar/39Ar study of a polymetamorphic complex in the Arunta Block,Central Australia

A polymetamorphic complex in the Arunta Block, Central Australia, which has undergone metasomatism involving introduction of Rb and loss of Sr has been investigated by ⁴⁰Ar/ ³⁹Ar step and total-degassing techniques in an attempt to date five metamorphic events (M1–M5) identified microstructurally. The complex isotopic data and apparent age spectra obtained have been interpreted in the light of constraints provided by an associated tectonometamorphic study, together with independent geochronological controls from the immediate study area and elsewhere in the Arunta Block. This has led to the delineation of ages of 1,780–1,820 M.y. for M1, 1,690–1,720 M.y. for M2, 1,450–1,500 M.y. for M3, 1,030–1,060 M.y. for M4 and 370–510 for M5. The polyphase M5 event is correlated with the Alice Springs Orogeny, previously accorded younger age limits of 330–370 M.y. The latter are interpreted to reflect closure of mica K/Ar systems as uplift continued subsequent to the close of the event, possibly culminating in minor high-level brittle deformation and the development of pseudotachylytes in the study area.Apparent age spectra recorded in this study do not all conform with generally accepted patterns of behaviour of mineral systems which have undergone polythermal histories. Two hornblendes have survived subsequent high temperature metasomatic reheating without loss of argon or resetting of their ages. Their resistance to argon loss may be attributable to low water contents, due to their growth under anhydrous granulite facies conditions, and may reflect a relationship between argon loss from hornblende and the water content of hornblende, which decreases with increasing metamorphic grade (Kostyuk and Sobolev 1969). Other samples display false plateaux in their apparent age spectra and in three cases the spectra are indistinguishable from those of undisturbed spectra.The age data recorded in this study suggest that during basement reactivation loss of argon is mainly confined to the vicinity of shear zones, implying that diffusion of argon from minerals in the deep crust may be dependent more on deformation than on reheating. However, thermal activity may also be associated with active shear zones, through the medium of superheated fluids streaming up the shear zones from below. The wide spread of K/Ar and ⁴⁰Ar/³⁹Ar ages (330–510 M.y.), recorded for the Alice Springs Orogeny in the Arunta basement, may reflect such controls.     

Favourable uranium–phosphate exploration trends guided by the application of statistical factor analysis technique on the aerial gamma spectrometric data in Syrian desert (Area-1), Syria

A scored lithological map including 10 radiometric units is established through applying factor analysis approach to aerial spectrometric data of Area-1, Syrian desert, which includes Ur, eU, eTh, K%, eU/eTh, eU/K%, and eTh/K%. A model of four rotated factors F1, F2, F3, and F4 is adapted for representing 234,829 data measured points in Area-1, where 86% of total data variance is interpreted. A geological scored pseudo-section derived from the lithological scored map is established and analyzed in order to show the possible stratigraphic and structural traps for uranium occurrences associated with phosphate deposits in the studied Area-1. These identified traps presented in this paper need detailed investigation and must be necessarily followed and checked by ground validations and subsurface well logging, in order to locate the anomalous uranium occurrences and explore with more confidence and certitude their characteristics as a function of depth.     

First data on the noble metal geochemistry of the rocks from the gabbro-anorthosite massifs of the Kalar group

This paper addresses the geochemical features of the noble metal disseminated sulfide and Timagnetite mineralization in the rocks of the Kalar group of autonomous gabbro-anorthosite massifs. The investigations suggest that this mineralization was formed in two stages. The first stage is related to the gabbroanorthosites proper and may be promising for low-sulfide PGE mineralization as well as PGE-bearing Ti-magnetite mineralization, while the second stage is linked to the ultrabasic intrusions associated with copper-nickel or chromite mineralization accompanying by PGE. The horizons of low-sulfide mineralization in the gabbro-anorthosites and copper-nickel mineralization in the dunite-pyroxenites are characterized by the Pd predominance over Pt, while the Cr-bearing and Ti-magnetite ores show the Pt predominance over Pd.