Ernst A.J. Burke

Raman microspectrometry of fluid inclusions

Abstract For many kinds of fluid inclusions, the coupling of microthermometry and Raman microspectrometry is still the only viable option to obtain compositions of single fluid inclusions. A review is given on the basis of 16 years of experience and helped with about 120 references of the instrumentation, analytical conditions and methodology of the application of Raman microspectrometry to gaseous, aqueous and hydrocarbon inclusions, and their daughter minerals.

Nomenclature of amphiboles : additions and revisions to the International Mineralogical Association's amphibole nomenclature

The introduction of a fifth amphibole group, the Na-Ca-Mg-Fe-Mn-Li group, defined by 0.50 < B(Mg,Fe2+,Mn2+,Li) < 1.50 and 0.50 ≤ B(Ca,Na) ≤ 1.50 a.f.p.u. (atoms per formula unit), with members whittakerite and ottoliniite, has been required by recent discoveries of B(LiNa) amphiboles. This, and other new discoveries, such as sodicpedrizite (which, here, is changed slightly, but significantly, from the original idealized formula), necessitate amendments to the IMA 1997 definitions of the Mg-Fe-Mn-Li, calcic, sodic-calcic and sodic groups. The discovery of obertiite and the finding of an incompatibility in the IMA 1997 subdivision of the sodic group, requires further amendments within the sodic group. All these changes, which have IMA approval, are summarized.

Nitrogen-bearing, aqueous fluid inclusions in some eclogites from the Western Gneiss Region of the Norwegian Caledonides

AbstractMinerals in eclogites from different localities in the Western Gneiss Region of the Norwegian Caledonides (age ≈425 Ma) contain a variety of fluid inclusions. The earliest inclusions recognized are contained in undeformed quartz grains, protected by garnet, and consist of H2O+N2 (with

Nitrogen-rich fluid in the upper mantle: fluid inclusions in spinel dunite from Lanzarote, Canary Islands

X_{{\text{H}}_{\text{2}} {\text{O}}} \geqslant 0.8

Evidence of magmatic CO2-rich fluids in peraluminous graphite-bearing leucogranites from Deep Freeze Range (northern Victoria Land, Antarctica)

). The reconstructed P-V-T-X properties of these fluid inclusions are compatible with peak or early-retrograde metamorphic conditions. Matrix minerals (quartz, garnet, apatite, plagioclase) contain a complex pattern of mostly truly secondary inclusions, dominated by CO2 and N2. The textural patterns and P-V-T-X properties of these inclusions are incompatible with the high pressures of the eclogite-forming metamorphic event, but suggest that they were formed during uplift, by a combination of remobilization of preexisting inclusions and influx of external fluids. The fluid introduced at a late stage was dominated by CO2, and did not contain N2. The present data agree with theoretical predictions of eclogite fluids from mineral equilibria, and highlight the differences between granulite (CO2) and eclogite (H2O+N2) fluid regimes. The provenance of the nitrogen in the eclogite fluid inclusions represents an important, but unsolved question in the petrology of high-pressure metamorphic rocks.

Origin and structural character of haüyness in spinel dunite xenoliths from La Palma, Canary Islands

Abstract High-pressure metamorphic rocks (eclogites and high-pressure granulites) occur along the entire length of the Norwegian Caledonides, and have formed from a variety of protoliths. In some cases, the relationship between protoliths, high-pressure rocks and their later retrogression products have been preserved in-situ. Fluid-inclusion data suggest a simple correlation between metamorphic grade and metamorphic fluid composition: (1) Eclogites and high-pressure granulites contain N 2 -bearing fluids (pure N 2 , or mixtures with CO 2 or H 2 O, with X N 2 > 5%). In some eclogite-facies rocks, CO 2 /1bN 2 inclusions are associated with aqueous brine inclusions (ca. 30 wt% NaCl), the two compositions representing immiscible fluids at peak metamorphic conditions. (2) Granulite -facies protoliths and eclogites reworked in the granulite-facies contain pure CO 2 or CO 2 -dominated fluids with less than 2.5% N 2 . (3) Rocks retrograded in the amphibolite facies contain H 2 O/1bNaCl fluids. Immiscibility between brine and anhydrous N 2 /1bCO 2 fluid, and between anhydrous fluid and waterbearing aluminosilicate-melt have taken place in some eclogites. During high-grade metamorphism, nitrogen may be incorporated in minerals, as NH 4 substituting for K, or it may occur as N 2 in the free fluid phase. The partitioning of nitrogen between minerals and fluids depends upon the water activity and oxygen fugacity during metamorphism, low a H 2 O and/or high f O 2 partitioning nitrogen to the fluid phase. A rock interacting with a carbonic fluid at granulite-facies PT conditions will be depleted in mineralogically bound nitrogen. In cases where the protoliths of high-pressure rocks have been through a previous, granulite-facies event, a local source for the nitrogen contained in high-pressure fluid is therefore unlikely.

Nomenclature of amphiboles: Additions and revisions to the International Mineralogical Associations amphibole nomenclature

Fluid inclusions, ranging from pure N2 to pure CO2, occur in olivine porphyroclasts in spinel dunite xenoliths (chrome-diopside suite) from two localities within the Quaternary to Historic alkaline lavas of Lanzarote, Canary Islands. This is the first report of fluid inclusions containing major amounts of N2 in mantle xenoliths. The nitrogen-rich fluid inclusions predate at least one generation of nitrogen-free carbon dioxide inclusions; textural evidence indicates that the inclusions were trapped within the upper mantle. Some of the nitrogen-rich fluid inclusions are intimately associated with solid inclusions of spinel. The nitrogen-rich fluid was most likely produced in-situ, by oxidation-dehydration reactions destabilizing ammonium-bearing silicate minerals (phlogopite, amphibole), increasing oxygen fugacity or, possibly, increasing temperature of the mantle. This process could be related to an event of CO2 and silicate melt injection at 6–8 kbar (Neumann et al., in press), or to some earlier event in the evolution of the mantle beneath Lanzarote. The existence of a N2-rich fluid phase in at least some mantle lithology(ies) at certain conditions is demonstrated by these data. This discovery has consequences for the understanding of the evolution of the mantle below the Canary Islands, as well as for the global nitrogen budget.

The IMA-CNMNC dominant-constituent rule revisited and extended

Abstract Felsic extension veins consisting of plagioclase (Ab 91 ), phengite, quartz, clinozoisite and minor/accessory calcite occur in the central parts of Caledonian eclogite-facies shear zones at Holsnoy island in the Bergen Arcs nappe complex. The veins have the field and textural characteristics of syntectonic intrusions and have crystallized at pressures and temperatures compatible with the peak of eclogite-facies metamorphism (ca. 700°C, 16–19 kbar). The quartz contains early (“primary”) fluid inclusions of (a) aqueous brine (31–34 wt.% NaCl) and (b) a CO 2 N 2 mixture with X N 2 ≥ 5 mole percent. The two fluids were present simultaneously and are interpreted as immiscible at the PT conditions of vein formation. Later generations of fluid inclusions comprise nitrogen-rich CO 2 N 2 mixtures and aqueous fluids with low salt contents. The latter were trapped at a late stage of the cooling and uplift history of the nappe complex. At the temperature of the peak of eclogite-facies metamorphism at Holsnoy (ca. 700°C), introduction of a fluid phase with high water activity caused partial melting of the surrounding mafic to intermediate lithologies; the muscovite-granite extension veins represent the crystallization products of anatectic melts migrating through the shear zones at eclogite-facies conditions.