A review of coastal dunebuilding in Eastern Australia

The distribution of transgressive coastal sand dunes in eastern New South Wales and Queensland is summarised and the factors involved in transgressive dune initiation are reviewed. On the basis of radiocarbon and pedological evidence, it is suggested that episodes of transgressive dune instability have been synchronous over large areas. Widespread sand blowing appears to have taken place in the early Holocene between 9,000 and 7,000 years ago. Instability was also widespread between 3,500 and 2,000 years ago and within the last thousand years. Possible causes of dune instability are considered.     

The age and growth of hottentot seabream Pachymetopon blochii before and after the South African linefish state of emergency in 2000

The hottentot seabream Pachymetopon blochii is a small-sized (maximum 2.67 kg) sparid endemic to southern Africa. It is an important target in South Africa's Western Cape traditional linefishery, particularly in the absence of more valuable pelagic species (such as Thyrsites atun and Seriola lalandi). In 2000, South Africa's linefishery was declared to be in a state of emergency, and commercial fishing effort was consequently reduced by 70%. A subsequent increase in stock biomass and intraspecific competition, coupled with environmental changes, were hypothesised to have thereafter altered the growth rate of hottentot, from 2000 to 2010. This study aimed to revise outdated age–growth models for the hottentot by using modern techniques (sectioned otoliths), and to compare age–growth relationships before and after the declared linefish state of emergency. The maximum age observed was 19 years, with no difference in the growth rate between sexes (p = 0.39–0.43) or time-periods (p = 0.96). Although the growth rate did not change, there is evidence that the age structure of the stock changed between time-periods as a result of changes in fishing pressure between 2000 and 2010. The enhanced recent growth model for hottentot, described as L_t = 418.063 (1 – e^{?0.104(t – [?4.709])}) (pooled sexes; n = 206), indicates a considerably slower growth rate for this species than was proposed previously using whole otoliths and has major implications for effective stock management.     

Five thousand years of sediment transfer in a high arctic watershed recorded in annually laminated sediments from Lower Murray Lake,Ellesmere Island,Nunavut, Canada

Sediments in Lower Murray Lake, northern Ellesmere Island, Nunavut Canada (81°21′ N, 69°32′ W) contain annual laminations (varves) that provide a record of sediment accumulation through the past 5000+ years. Annual mass accumulation was estimated based on measurements of varve thickness and sediment bulk density. Comparison of Lower Murray Lake mass accumulation with instrumental climate data, long-term records of climatic forcing mechanisms and other regional paleoclimate records suggests that lake sedimentation is positively correlated with regional melt season temperatures driven by radiative forcing. The temperature reconstruction suggests that recent temperatures are ~2.6°C higher than minimum temperatures observed during the Little Ice Age, maximum temperatures during the past 5200 years exceeded modern values by ~0.6°C, and that minimum temperatures observed approximately 2900 varve years BC were ~3.5°C colder than recent conditions. Recent temperatures were the warmest since the fourteenth century, but similar conditions existed intermittently during the period spanning ~4000–1000 varve years ago. A highly stable pattern of sedimentation throughout the period of record supports the use of annual mass accumulation in Lower Murray Lake as a reliable proxy indicator of local climatic conditions in the past.

A contribution to the migration of gold in the biosphere of the humid mild zone

The content of gold in plants has been used as an indicator in the prospecting for gold. For this purpose non-destructive analytical methods have been developed. In the humid mild zone — where the process of weathering is of a kaolinitic character — there is practically no migration of gold, and consequently its increased content indicates the presence of a gold deposit.     

Impacts of Invasive <Emphasis Type="Italic">Phragmites australis</Emphasis> on Diamondback Terrapin Nesting in Chesapeake Bay

The range expansion of exotic plant species, including the invasive reed Phragmites australis, causes widespread structural and functional changes to coastal ecosystems along the Atlantic and Gulf Coasts of North America. Native estuarine species, such as the diamondback terrapin (Malaclemys terrapin), are at risk of adverse effects from rapid habitat changes due to exotic invasions. Diamondback terrapins currently face population threats including by-catch mortality in crab pots, predation, and habitat loss, and populations may continue to suffer if deleterious plant invasions into preferred nesting habitats are left unchecked. We examined the extent to which Phragmites affects nesting of a breeding population of diamondback terrapins at Fisherman Island National Wildlife Refuge on the eastern shore of Virginia, where Phragmites has recently expanded into known areas of terrapin nesting. With data collected from the 2015 nesting season, we quantified the extent to which Phragmites shading could impact nest incubation temperature and determined how Phragmites density impacts the risk of rhizome invasion into nests. We conclude that Phragmites cover greater than 50% would decrease incubation temperatures of terrapin nests sufficiently to produce predominantly male hatchlings. Phragmites cover had no observed effect on root growth into simulated nests, but cover by other dune plant species explained observed trends in root growth. These results suggest that terrapins may be negatively impacted by Phragmites expansion into open nesting sites. Breeding site fidelity exhibited by terrapins and other estuarine species could limit the ability of their populations to adjust to rapid coastal expansion of invasive plant species.     

Shoshonitic lamprophyre dykes and their relation to mesothermal Au---Sb veins at Hillgrove, New South Wales, Australia

The Hillgrove mineral field, in the southern part of the New England Orogen of northeastern New South Wales, Australia, contains numerous mesothermal Au---Sb vein systems. Calc-alkaline (shoshonitic) lamprophyre (CAL) dykes are also associated with mineralisation with dilational lode structures acting as conduits for dyke intrusion, which has occurred before and after major quartz-stibnite veining. Dykes include minette and vogesite compositions and were emplaced in the late Permian (247–255 Ma), at the same time as regionally extensive I-type magmatism in the New England Orogen. Least-altered dykes are enriched in Mg, K, Ba, Rb, Sr, Zr, Th, Cr and Ni relative to I-type intrusives although chemical affinities are evident between lamprophyres and the more mafic members of the high-K Moonbi Plutonic Suite.

Hillgrove lamprophyres are commonly enriched in Sb, As, Hg, Au, W and Bi with respect to average CAL compositions. Evidence indicates this is most likely due to contamination of magma during intrusion through mineralised structures, rather than a primary magmatic feature. Partially resorbed xenocrystic stibnite occurs in dykes which have intruded lode structures, probably facilitated by the low melting point of stibnite (550°C) and its incorporation into the magma. Carbon and oxygen isotopic data from carbonates in least-altered, post-lode lamprophyres are indistinguishable from carbonate in altered dykes and veins, implying that hydrothermal interaction continued after dyke intrusion. Although it is unlikely that lamprophyre dykes have been a direct source for mineralisation at Hillgrove, the close temporal and spatial relation of dykes, mesothermal Au---Sb veins and I-type intrusions are interpreted to be manifestations of the post-collisional setting and influx of mantle-derived heat and partial melts into the New England Orogen during the late Permian.     

Mineralogy and textural relationships among sulphosalts and related minerals in the Bleikvassli Zn-Pb-(Cu) deposit, Nordland, Norway

Several distinct assemblages of Pb-Sb, Pb-As, Cu-Pb-Sb and Cu-Fe-Zn-Sn sulphosalts are identified in sulphide samples from Bleikvassli mine, Norway. Detailed optical microscopy and electron probe microanalysis have permitted investigation of textural relationships between minerals and compositional variations between different ore types. Tetrahedrite, typically containing 10–16?wt.% Ag (rare freibergite containing 25–30?wt.% Ag has also been identified in two samples), stannite (Cu₂(Fe>Zn)SnS₄), and meneghinite, CuPb₁₃Sb₇S₂₄, are widely distributed as trace constituents throughout massive pyritic and galena-rich ores. Native antimony and pyrargyrite occur in trace amounts in all ore types, as the breakdown products of earlier sulphosalts. Several distinct types of wall-rock mineralisation are present at Bleikvassli. Of considerable mineralogical interest are the coarse-grained sulphide mobilisates within the wall rock which contain a distinct?and characteristic suite of Pb-As sulphosalts:?tennantite?+?jordanite (Pb₁₄As₆S₂₃)?+?seligmannite (CuPbAsS₃) ± dufrenoysite (Pb₂As₂S₅). Bournonite (CuPbSbS₃) is the only Sb-bearing sulphosalt recognised in significant amounts within the mobilisates, meneghinite and tetrahedrite being conspicuously absent. These mobilisates display considerable Au enrichment; electrum can be confirmed, intimately associated with jordanite and tennantite. Appreciable Sb (up to 3?wt.%) is contained within galena in the mobilisates, in contrast to galena from massive ores which contains only negligible Sb. Contents of Ag and Bi in galena vary considerably in all ore types, but confirm earlier suggestions that galena is a major Ag-carrier at Bleikvassli. Boulangerite (Pb₅Sb₄S₁₁), jamesonite (FePb₄Sb₆S₁₄) and gudmundite (FeSbS) occur in trace amounts. Sn-sulphosalts are represented by kësterite, (Cu₂(Zn> Fe)SnS₄), but commonly zoned with respect to Zn/Fe ratio, in the mobilisates, rather than by stannite. A rare type of mobilisate, also in the wall rock, in which chalcocite and bornite are the main minerals, contains native Ag, stromeyerite (AgCuS), mckinstryite ((Ag,Cu)₂?S), Ag-free tetrahedrite, an unnamed Cu-Ag-Fe sulphide (Cu₃Ag₂FeS₄) and native Bi, myrmekitically intergrown with chalcocite. Although a comprehensive genetic model for the wall-rock mineralisation at Bleikvassli is largely impossible given the limitations in the present state of knowledge regarding mechanisms involved in remobilisation processes, a multi-stage model of remobilisation during regional metamorphism is considered to best explain the observations. An interplay of different solid- and liquid-state remobilisation mechanisms, in various combinations, is required to account for the macro- and microscopic observations. Remobilisation probably began during the earlier stages of metamorphism, with crystallisation and further remobilisation taking place during the entire metamorphic cycle, giving rise to the extensive chemical and mineralogical diversity observed today. Preserved mineral assemblages and their textural relationships reflect a complex sequence of replacement and decomposition reactions taking place during the latest phase of late-metamorphic crystallisation and subsequent cooling.     

Trace and minor elements in sphalerite: A LA-ICPMS study

Sphalerite is an important host mineral for a wide range of minor and trace elements. We have used laser-ablation inductively coupled mass spectroscopy (LA-ICPMS) techniques to investigate the distribution of Ag, As, Bi, Cd, Co, Cu, Fe, Ga, Ge, In, Mn, Mo, Ni, Pb, Sb, Se, Sn and Tl in samples from 26 ore deposits, including specimens with wt.% levels of Mn, Cd, In, Sn and Hg. This technique provides accurate trace element data, confirming that Cd, Co, Ga, Ge, In, Mn, Sn, As and Tl are present in solid solution. The concentrations of most elements vary over several orders of magnitude between deposits and in some cases between single samples from a given deposit. Sphalerite is characterized by a specific range of Cd (typically 0.2-1.0 wt.%) in each deposit. Higher Cd concentrations are rare; spot analyses on samples from skarn at Baisoara (Romania) show up to 13.2 wt.% (Cd²⁺ ↔ Zn²⁺ substitution). The LA-ICPMS technique also allows for identification of other elements, notably Pb, Sb and Bi, mostly as micro-inclusions of minerals carrying those elements, and not as solid solution. Silver may occur both as solid solution and as micro-inclusions. Sphalerite can also incorporate minor amounts of As and Se, and possibly Au (e.g., Magura epithermal Au, Romania). Manganese enrichment (up to ∼4 wt.%) does not appear to enhance incorporation of other elements. Sphalerite from Toyoha (Japan) features superimposed zoning. Indium-sphalerite (up to 6.7 wt.% In) coexists with Sn-sphalerite (up to 2.3 wt.%). Indium concentration correlates with Cu, corroborating coupled (Cu⁺In³⁺) ↔ 2Zn²⁺ substitution. Tin, however, correlates with Ag, suggesting (2Ag⁺Sn⁴⁺) ↔ 3Zn²⁺ coupled substitution. Germanium-bearing sphalerite from Tres Marias (Mexico) contains several hundred ppm Ge, correlating with Fe. We see no evidence of coupled substitution for incorporation of Ge. Accordingly, we postulate that Ge may be present as Ge²⁺ rather than Ge⁴⁺. Trace element concentrations in different deposit types vary because fractionation of a given element into sphalerite is influenced by crystallization temperature, metal source and the amount of sphalerite in the ore. Epithermal and some skarn deposits have higher concentrations of most elements in solid solution. The presence of discrete minerals containing In, Ga, Ge, etc. also contribute to the observed variance in measured concentrations within sphalerite.