Gahnite and columbite in an alkali-feldspar granite from New Zealand

1981 ◽  
Vol 44 (335) ◽  
pp. 275-278 ◽  
Author(s):  
A. J. Tulloch
Keyword(s):  
New Zealand ◽  
Fractional Crystallization ◽  
Alkali Feldspar ◽  
Mafic Mineral ◽  
Granitoid Rocks ◽  
Highly Evolved

AbstractGahnite and columbite with compositions (Zn5.96Fe1.55Mg0.21Mn0.13)Σ7.85Al16.09O32 and (Nb7.36Ta0.60Mn2.95Fe0.98Ti0.09)Σ11.98O24 occur as accessory phases in a highly evolved garnetiferous muscovite alkalifeldspar granite. Both phases have developed as a result of a concentration of Zn, Nb, and Ta during the fmal stages of the fractional crystallization which led to the formation of the pluton, and the lack of a major mafic mineral such as biotite, in which these elements are normally camouflaged in granitoid rocks.

scholarly journals New Zealand White Rabbits Effectively ClearBorrelia burgdorferiB31 despite the Bacterium’s FunctionalvlsEAntigenic Variation System

2019 ◽  
Vol 87 (7) ◽  
Author(s):  
Maliha Batool ◽  
Andrew E. Hillhouse ◽  
Yurij Ionov ◽  
Kelli J. Kochan ◽  
Fatemeh Mohebbi ◽  
...  
Keyword(s):  
New Zealand ◽  
Persistent Infection ◽  
Antigenic Variation ◽  
Surface Expression ◽  
The United States ◽  
Antimicrobial Treatment ◽  
Current Data ◽  
Content Type ◽  
Highly Evolved

ABSTRACTBorrelia burgdorferiis a tick-borne bacterium responsible for approximately 300,000 annual cases of Lyme disease (LD) in the United States, with increasing incidences in other parts of the world. The debilitating nature of LD is mainly attributed to the ability ofB. burgdorferito persist in patients for many years despite strong anti-Borreliaantibody responses. Antimicrobial treatment of persistent infection is challenging. Similar to infection of humans,B. burgdorferiestablishes long-term infection in various experimental animal models except for New Zealand White (NZW) rabbits, which clear the spirochete within 4 to 12 weeks. LD spirochetes have a highly evolved antigenic variationvlssystem, on the lp28-1 plasmid, where gene conversion results in surface expression of the antigenically variable VlsE protein. VlsE is required forB. burgdorferito establish persistent infection by continually evading otherwise potent antibodies. Since the clearance ofB. burgdorferiis mediated by humoral immunity in NZW rabbits, the previously reported results that LD spirochetes lose lp28-1 during rabbit infection could potentially explain the failure ofB. burgdorferito persist. However, the present study unequivocally disproves that previous finding by demonstrating that LD spirochetes retain thevlssystem. However, despite thevlssystem being fully functional, the spirochete fails to evade anti-Borreliaantibodies of NZW rabbits. In addition to being protective against homologous and heterologous challenges, the rabbit antibodies significantly ameliorate LD-induced arthritis in persistently infected mice. Overall, the current data indicate that NZW rabbits develop a protective antibody repertoire, whose specificities, once defined, will identify potential candidates for a much-anticipated LD vaccine.

The timing of Proterozoic magmatism in the Pinware terrane of southeast Labrador, easternmost Quebec and northwest Newfoundland

2004 ◽  
Vol 41 (2) ◽  
pp. 127-150 ◽  
Author(s):  
L M Heaman ◽  
C F Gower ◽  
S Perreault
Keyword(s):  
Long Range ◽  
Alkali Feldspar ◽  
Geochronological Data ◽  
Grenville Province ◽  
Mafic Magmatism ◽  
Granitoid Rocks ◽  
Red Bay ◽  
High Level ◽  
First Time ◽  
Magmatic Event

The Pinware terrane is located in the easternmost Grenville Province and contains crust of Labradorian (1710–1600 Ma), Pinwarian (1520–1460 Ma), Elsonian (1460–1230 Ma), Grenvillian (1080–985 Ma), and late- to post-Grenvillian (985–955 Ma) age. Newly obtained U–Pb geochronological data enhance understanding of all these evolutionary stages. A Labradorian age of 1632 ± 8 Ma has been obtained for the Brador River granite, thereby establishing the presence of mid- to late- Labradorian rocks in the southernmost part of the region. A maximum age of ~1600 Ma obtained for the Ten Mile Lake granite indicates for the first time that Labradorian crust could continue into the northern Long Range Inlier of western Newfoundland. Pinwarian activity is indicated by ages of ~1526–1504, 1500 ± 14, 1467 ± 44, and 1466 ± 8 Ma from granitoid rocks at Rivière St-Paul, West St. Modeste, Diable Bay, and Pinware, respectively. The first evidence for late Elsonian mafic magmatism in this region is provided by a concordant baddeleyite date of 1248 ± 5 Ma from gabbronorite at Lourdes-de-Blanc-Sablon. This study has also identified an early post-tectonic, high-level, mafic–anorthositic–syenitic magmatic event between 985 and 975 Ma. Recognition of the event relies on previous results and newly obtained ages of 979.5 ± 2.8 Ma from the Red Bay gabbro, 974.5 ± 1.8 Ma from the Vieux Fort anorthosite, and 969 ± 11 Ma from the Lower Pinware River alkali-feldspar syenite. Time, composition, and fabric criteria distinguish these rocks from late-post-tectonic monzonite, syenite and granite emplaced between 966 and 956 Ma.

Petrology of the alkali syenites of the Mundwara magmatic suite, Sirohi, Rajasthan, India

1973 ◽  
Vol 110 (5) ◽  
pp. 457-466 ◽  
Author(s):  
M. K. Bose ◽  
D. K. Das Gupta
Keyword(s):  
Comparative Study ◽  
Alkali Feldspar ◽  
Western India ◽  
Variable Degree ◽  
Deccan Volcanic Province ◽  
Volcanic Province ◽  
Mafic Mineral ◽  
Magmatic Suite ◽  
Calciferous Amphibole ◽  
North Western

SummaryThe alkali syenites of the Mundwara magmatic suite, Sirohi district, Rajasthan, in north-western India, are chiefly developed in the Musala hill of the complex. They comprise three principal varieties representing different stages of crystallization, viz. nepheline-sodalite syenite, nepheline-barkevikite microsyenite, and nepheline poor leucosyenite. The dominant constituent of these hypersolvus syenites is alkali feldspar, an orthoclase microperthite showing a variable degree of exsolution. The chief mafic mineral is a distinctly green and zoned sodic pyroxene, close to aegirine-augite in composition. A brown calciferous amphibole, identified as a barkevikite, is developed in addition in the microsyenites. Reddish brown biotite of the phlogopite-annite series is common to all the syenites. The petrography and mineralogy of the syenites are discussed, and a comparative study of the Mundwara syenites with similar rocks of the Deccan volcanic province is presented. Chemistry and mineralogy of the syenites of the Mundwara suite suggest that they are related to those associated with the Deccan volcanic province.

scholarly journals Compositions of some granitoid rocks from Westland, New Zealand

1989 ◽  
Vol 19 (1) ◽  
pp. 55-58
Author(s):  
Brian Mason
Keyword(s):  
New Zealand ◽  
Granitoid Rocks

scholarly journals Accessory minerals and evolution of tin-bearing S-type granites in the western segment of the Gemeric Unit (Western Carpathians)

2018 ◽  
Vol 69 (5) ◽  
pp. 483-497 ◽  
Author(s):  
Igor Broska ◽  
Michal Kubiš
Keyword(s):  
Mineral Assemblage ◽  
Alkali Feldspar ◽  
Rare Metal ◽  
Tectonic Activity ◽  
Accessory Mineral ◽  
Porphyritic Granite ◽  
Western Segment ◽  
Gemeric Unit ◽  
Highly Evolved

Abstract The S-type accessory mineral assemblage of zircon, monazite-(Ce), fluorapatite and tourmaline in the cupolas of Permian granites of the Gemeric Unit underwent compositional changes and increased variability and volume due to intensive volatile flux. The extended S-type accessory mineral assemblage in the apical parts of the granite resulted in the formation of rare-metal granites from in-situ differentiation and includes abundant tourmaline, zircon, fluorapatite, monazite-(Ce), Nb–Ta–W minerals (Nb–Ta rutile, ferrocolumbite, manganocolumbite, ixiolite, Nb–Ta ferberite, hübnerite), cassiterite, topaz, molybdenite, arsenopyrite and aluminophosphates. The rare-metal granites from cupolas in the western segment of the Gemeric Unit represent the topaz–zinnwaldite granites, albitites and greisens. Zircon in these evolved rare-metal Li–F granite cupolas shows a larger xenotime-(Y) component and heterogeneous morphology compared to zircons from deeper porphyritic biotite granites. The zircon Zr/Hfwt ratio in deeper rooted porphyritic granite varies from 29 to 45, where in the differentiated upper granites an increase in Hf content results in a Zr/Hfwt ratio of 5. The cheralite component in monazite from porphyritic granites usually does not exceed 12 mol. %, however, highly evolved upper rare-metal granites have monazites with 14 to 20 mol. % and sometimes > 40 mol. % of cheralite. In granite cupolas, pure secondary fluorapatite is generated by exsolution of P from P-rich alkali feldspar and high P and F contents may stabilize aluminophosphates. The biotite granites contain scattered schorlitic tourmaline, while textural late-magmatic tourmaline is more alkali deficient with lower Ca content. The differentiated granites contain also nodular and dendritic tourmaline aggregations. The product of crystallization of volatile-enriched granite cupolas are not only variable in their accessory mineral assemblage that captures high field strength elements, but also in numerous veins in country rocks that often contain cassiterite and tourmaline. Volatile flux is documented by the tetrad effect via patterns of chondrite normalized REEs (T1,3 value 1.46). In situ differentiation and tectonic activity caused multiple intrusive events of fluid-rich magmas rich in incompatible elements, resulting in the formation of rare-metal phases in granite roofs. The emplacement of volatile-enriched magmas into upper crustal conditions was followed by deeper rooted porphyritic magma portion undergoing second boiling and re-melting to form porphyritic granite or granite-porphyry during its ascent.

scholarly journals Potassium and Metal Release Related to Glaucony Dissolution in Soils

Soil Systems ◽  
2019 ◽  
Vol 3 (4) ◽  
pp. 70 ◽  
Author(s):  
Oze ◽  
Smaill ◽  
Reid ◽  
Palin
Keyword(s):  
New Zealand ◽  
Solid Phase ◽  
Chemical Analyses ◽  
Metal Release ◽  
Environmentally Sustainable ◽  
Spatially Resolved ◽  
Soil Systems ◽  
Low Concentrations ◽  
K Release ◽  
Highly Evolved

Plant nutrients such as potassium (K) may be limited in soil systems and additions (i.e., fertilizer) are commonly required. Glaucony is a widely distributed and abundant marine-derived clay mineral present in soils worldwide which may serve as a source of potassium. The South Island of New Zealand contains numerous deposits of glaucony-rich rocks and related soils providing an opportunity to explore how glaucony might be a beneficial source of potassium. Here, the geochemistry of glaucony and its suitability as a mineral source of soil K from four deposits in New Zealand was examined using spatially resolved chemical analyses and dissolution experiments. Geochemical and morphological analyses revealed that glaucony from all deposits were K-enriched and were of the evolved (6%–8% K2O) to highly evolved type (>8% K2O). Glaucony derived from growth inside pellets contain elevated K and Fe concentrations compared to bioclast-hosted glaucony. Solubility analysis showed that K was released from glaucony at rates higher than any other metal present in the mineral. Additionally, decreasing the pH and introducing an oxidizing agent (i.e., birnessite which is ubiquitous in soil environments) appeared to accelerate K release. Trace metals including Cr, Zn, Cu, and Ni were present in the solid phase analysis; however, further investigation with a focus on Cr revealed that these elements were released into solution at low concentrations and may present a source of soil micronutrients. These results suggest that glaucony may offer a source of slow releasing K into soils, and so could be used as a locally sourced environmentally sustainable K resource for agriculture, whether in New Zealand or worldwide

Pétrologie du granite peralcalin du lac Brisson, Labrador central, Nouveau-Québec. II. Minéralogie et modalités de cristallisation

1993 ◽  
Vol 30 (12) ◽  
pp. 2423-2435 ◽  
Author(s):  
D. Pillet ◽  
M. Chenevoy ◽  
M. Bélanger
Keyword(s):  
Late Stage ◽  
Fluid Phase ◽  
Alkali Feldspar ◽  
Stability Field ◽  
Residual Liquid ◽  
Accessory Minerals ◽  
Mafic Mineral ◽  
Peralkaline Granite ◽  
Zirconium Silicate

Mineral zonation in the Québec–Labrador Brisson Lake peralkaline granite displays quartzose and feldspathic lithofacies arranged concentrically, the latter occupying the centre of the intrusion. The zonation is the result of successive magmatic pulses. In the feldspathic facies, agpaitic crystallization began under hypersolvus conditions around 720 °C with PF = 0.1 GPa. Subsolvus crystallization involving enrichment of the residual liquid in F continued to below 500 °C. The quartzose facies is more differentiated and its composition was controlled by feldspar fractionation. Early quartz crystallization is partly explained by the high content of F in the magma. The mafic mineral succession is, in both facies: Li- and Zn-rich arfvedsonite with an important ferrorichtérite component, which crystallized along with alkali feldspar under low [Formula: see text]; aenigmatite contemporary of amphibole or anterior, destabilized to form neptunite, astrophyllite, aegirine, or arfvedsonite; primary titaniferous aegyrine, contemporary with the amphibole and replaced by secondary aegyrine; neptunite and astrophyllite replacing aenigmatite. This succession is in accordance with the increase of Na and F in the fluid phase, and the increase of [Formula: see text] near the end of crystallization. Among the accessory minerals, euhedral zircon is indicative of the initial richness of the magma in Zr. Magmatic vlasovite, and elpidite formed from late fluid, are evidence that residual system entered the zirconium silicate stability field. Zircon with a fibrous, radiating texture, and gittinsite are indicative of the postmagmatic evolution of the pluton and the presence of a late stage residual fluid which was enriched in Ca and Sr.

The Petrology of the Tarosero Volcanic Complex: Constraints on the formation of extrusive agpaitic rocks

2021 ◽  
Author(s):  
S Braunger ◽  
M A W Marks ◽  
T Wenzel ◽  
A N Zaitsev ◽  
G Markl
Keyword(s):  
Trace Element ◽  
Water Activity ◽  
Fractional Crystallization ◽  
Genetic Relationships ◽  
Alkali Feldspar ◽  
High Water ◽  
Low Pressure ◽  
Water Soluble ◽  
Volcanic Complex ◽  
Rock Types

Abstract The Quaternary Tarosero volcano is situated in the East African Rift of northern Tanzania and mainly consists of trachyte lavas and some trachytic tuffs. In addition, there are minor occurrences of extrusive basalts, andesites, latites, as well as peralkaline trachytes, olivine trachytes and phonolites. Some of the peralkaline phonolites contain interstitial eudialyte, making Tarosero one of the few known occurrences for extrusive agpaitic rocks. This study investigates the genetic relationships between the various rock types and focuses on the peculiar formation conditions of the extrusive agpaitic rocks using a combination of whole-rock geochemistry, mineral chemistry, petrography, thermodynamic calculations, as well as major and trace element modelling. The Tarosero rocks formed at redox conditions around or below the fayalite-magnetite-quartz buffer (FMQ). During multi-level magmatic fractionation at depths between ∼40 km and the shallow crust, temperature decreased from > 1100 °C at near-liquidus conditions in the basalts to ∼ 700 °C in the peralkaline residue. Fractional crystallization models and trace element characteristics do not indicate a simple genetic relationship between the trachytes and the other rock types at Tarosero. However, the genetic relationships between the primitive basalts and the intermediate latites can be explained by high pressure fractional crystallization of olivine + clinopyroxene + magnetite + plagioclase + apatite. Further fractionation of these mineral phases in addition to amphibole and minor ilmenite led to the evolution towards the peralkaline trachytes and phonolites. The eudialyte-bearing varieties of the peralkaline phonolites required additional low-pressure fractionation of alkali feldspar and minor magnetite, amphibole and apatite. In contrast to the peralkaline trachytes and phonolites, the peralkaline olivine trachytes contain olivine instead of amphibole, thus indicating a magma evolution at even lower pressure conditions. They can be modelled as a derivation from the latites by fractional crystallization of plagioclase, clinopyroxene, magnetite and olivine. In general, agpaitic magmas evolve under closed system conditions which impedes the escape of volatile phases. In case of the extrusive agpaitic rocks at Tarosero, the early exsolution of fluids and halogens was prevented by a low water activity. This resulted in high concentrations of Rare Earth Elements (REE) and other High Field Strength Elements (HFSE) and the formation of eudialyte in the most evolved peralkaline phonolites. Within the peralkaline rock suite, the peralkaline olivine trachytes contain the lowest HFSE and REE concentrations, consistent with mineralogical evidence for a formation at a relatively high water activity. The lack of amphibole fractionation, which can act as a water buffer of the melt, as well as the evolution at relatively low pressure conditions caused the early exsolution of fluids and loss of water-soluble elements. This prevented a strong enrichment of HFSE and REE before the magma finally extruded.

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