A potential zircon reference material (BB zircon) for laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) U-Pb geochronology and Hf isotope geochemistry is described. A batch of twenty zircon megacrysts (0.5–1.5 cm3) from Sri Lanka was studied. Within-grain rare earth element (REE) compositions are largely homogeneous, albeit with some variation seen between fractured and homogeneous domains. Excluding fractured cathodoluminescence bright domains, the variation in U content for all analysed crystals ranged from 227 to 368 μg g−1 and the average Th/U ratios were between 0.20 and 0.47. The Hf isotope composition (0.56–0.84 g/100 g Hf) is homogeneous within and between the grains – mean 176Hf/177Hf of 0.281674 ± 0.000018 (2s). The calculated alpha dose of 0.59 × 1018 g−1 for a number of BB grains falls within the trend of previously studied, untreated zircon samples from Sri Lanka. Aliquots of the same crystal (analysed by ID-TIMS in four different laboratories) gave consistent U-Pb ages with excellent measurement reproducibility (0.1–0.4% RSD). Interlaboratory assessment (by LA-ICP-MS) from individual crystals returned results that are within uncertainty equivalent to the TIMS ages. Finally, we report on within- and between-grain homogeneity of the oxygen isotope systematic of four BB crystals (13.16‰ VSMOW).

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A new appraisal of sri lankan bb zircon as a reference material for LA-ICP-MS U-Pb geochronology and Lu-Hf isotope tracing.

Non-pegmatitic occurrences of Be minerals constitute a diverse set of geologic environments of considerable mineralogical and petrological interest; they currently provide the majority of the world’s Be ore and emeralds and they contain the greatest resource of these commodities. Of the approximately 100 Be minerals known (see Chapter 1 by Grew; Appendix A⇓), most occur in hydrothermal deposits or non-pegmatitic igneous rocks, where their distribution varies systematically with the setting and origin (Table 1⇓, Fig. 1⇓).

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 Table 1. 
Beryllium minerals in non-pegmatitic deposits: formulas, use and occurrence.1





 Figure 1. 
Chemography of the principal solid phases in the BeO-Al2O3-SiO2-H2O(-F2O−1) “BASH” system with the projected positions of helvite group and alkali Be silicates. Also shown are generalized fields for some of the major types natural of occurrences (cf. Table 1⇑, Fig. 4⇓; see text for discussion).



Beryllium minerals are best known from geologic systems associated with felsic magmatism. They also occur in a variety of settings that lack evident igneous associations. Environments range from the surface to the deep crust and host rocks range from feldspathic to carbonate to ultramafic in composition. Genetically related igneous rocks are felsic and share low calcium and high F contents, but are diverse in composition, setting and origin. Compositions range from strongly peraluminous to peralkaline and can be silica undersaturated. Beryllium minerals also occur in metamorphic and basinal environments and are redistributed by surface processes. Table 2⇓ summarizes the types and significance of major groups of occurrences by their lithologic associations. Figure 2⇓ shows the global distribution of some important examples and regional belts. For most types, at least one example has been described in some detail and can be used to help evaluate general patterns; however, …

Non-pegmatitic Deposits of Beryllium: Mineralogy, Geology, Phase Equilibria and Origin

Sri Lanka occupies a unique geologic position in Gondwana. Recent age and isotopic data suggest that the high‐grade basement rocks of Sri Lanka are more closely associated with the southeastern part of Madagascar than with the Archean granulites of southern and eastern parts of India. The occurrences of gem minerals and graphite in the centrally located Highland Complex of Sri Lanka can also be correlated with those of the Kerala Khondalite Belt (KKB) at the southern tip of India and of southeast Madagascar south of the Ranotsara Shear Zone. These geological and mineralogical features indicate the juxtaposition of Sri Lanka with Madagascar and also with the Lutzow‐Holm Bay area in Antarctica. The very close juxtaposition of Sri Lanka with Madagascar suggested here, which has hitherto been given only passing reference, implies that there exists a distinct mineralized belt running from Antarctica through the Highland Complex of Sri Lanka into Madagascar, Mozambique, Tanzania, and farther north. Thi...

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Sri Lanka–Madagascar Gondwana Linkage: Evidence for a Pan‐African Mineral Belt

China started to produce rare earth elements (REEs) in the 1980s, and since the mid-1990s, it has become the dominant producer. Rare earth element export quotas first introduced by the Chinese government in the early 2000s were severely reduced in 2010 and 2011. This led to strong government-created disparity between prices within China and the rest of the world. Industrialized countries identified several REEs as strategic metals. Because of rapid price increases of REE outside of China, we have witnessed a world-scale REE exploration rush. The REE resources are concentrated in carbonatite-related deposits, peralkaline igneous rocks, pegmatites, monazite ± apatite veins, ion adsorption clays, placers, and some deep ocean sediments. REE could also be derived as a by-product of phosphate fertilizer production, U processing, mining of Ti-Zr-bearing placers, and exploitation of Olympic Dam subtype iron oxide copper gold (IOCG) deposits. Currently, REEs are produced mostly from carbonatite-related deposits, but ion adsorption clay deposits are an important source of heavy REE (HREE). Small quantities of REE are derived from placer deposits and one peralkaline intrusion-related deposit. The ideal REE development targets would be located in a politically stable jurisdiction with a pro-mining disposition such as Canada and Australia. REE grade, HREE/light REE (LREE) ratio of the mineralization, tonnage, mineralogy, and permissive metallurgy are some of the key technical factors that could be used to screen potential development projects. As REEs are considered strategic metals from economic, national security, and environmental points of view, technical and economic parameters alone are unlikely to be used in REE project development decision-making. Recycling of REE is in its infancy and unless legislated, in the short term, it is not expected to contribute significantly to the supply of REE.

Geology and market-dependent significance of rare earth element resources

A classification of gem corundum deposits aimed towards gem exploration

Charnockites and the genesis of gem minerals

Erosion and sedimentation have a devastating effect on the environment of Sri Lanka. The Central Highlands with very steep slopes and a radial network of rivers that begin in these mountainous regions cause major erosional hazards, often resulting in disastrous landslides. Mining, particularly gem mining, has been responsible for serious problems of soil erosion and river siltation. A large number of illegal mines leave mine spoils resulting in damage to nearby paddy fields, crops, rivers and streams. Extensive sand mining in some rivers has lead to the collapse of river banks, destabilising structures such as bridges and causing influx of salt water. Landslides and coastal erosion are other factors that have had a negative impact on the environment in Sri Lanka.

M.S. Rupasinghe

Papers

Charnockites and the genesis of gem minerals

Environmental impact of mining, erosion and sedimentation in Sri Lanka

A prospectors' guide map to the gem deposits of Sri Lanka

The heavy metal pollution of the Kelani River in Sri Lanka

The rare-earth element abundance in the sedimentary gem deposits of Sri Lanka