Fluid and Solid Inclusions in Host Minerals of Permian Pegmatites from Koralpe (Austria): Deciphering the Permian Fluid Evolution during Pegmatite Formation

Fluid inclusions (FIs) and associated solids in host minerals garnet, tourmaline, spodumene, and quartz from six pegmatite fields of Permian origin at Koralpe (Eastern Alps) have been investigated. Although pegmatites suffered intense Eoalpine high-pressure metamorphic overprint during the Cretaceous period, the studied samples originate from rock sections with well-preserved Permian magmatic textures. Magmatic low-saline aqueous FIs in garnet domains entrapped as part of an unmixed fluid together with primary N2-bearing FIs that originate from a host rock-derived CO2-N2 dominated high-grade metamorphic fluid. This CO2-N2 fluid is entrapped as primary FIs in garnet, tourmaline, and quartz. During host mineral crystallization, fluid mixing between the magmatic and the metamorphic fluid at the solvus formed CO2-N2-H2O–rich FIs of various compositional degrees that are preserved as pseudo-secondary inclusions in tourmaline, quartz, and as primary inclusions in spodumene. Intense fluid modification processes by in-situ host mineral–fluid reactions formed a high amount of crystal-rich inclusions in spodumene but also in garnet. The distribution of different types of FIs enables a chronology of pegmatite host mineral growth (garnet-tourmaline/quartz-spodumene) and their fluid chemistry is considered as having exsolved from the pegmatite parent melt together with the metamorphic fluid from the pegmatite host rocks. Minimum conditions for pegmatite crystallization of ca. 4.5–5.5 kbar at 650–750 °C have been constrained by primary FIs in tourmaline that, unlike to FIs in garnet, quartz, and spodumene, have not been affected by post-entrapment modifications. Late high-saline aqueous FIs, only preserved in the recrystallized quartz matrix, are related to a post-pegmatite stage during Cretaceous Eoalpine metamorphism.

Quantification of major and trace elements in fluid inclusions and gas bubbles by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) with no internal standard: a new method

Recent advances in laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) open new perspectives for quantification of trace metals and metalloids in mineral-hosted fluid inclusions and glass-hosted gas bubbles. This work is devoted to a new method applied to quantify element concentrations (at parts-per-million and weight percent levels) in natural and synthetic fluid inclusions and gas bubbles by using only an external calibrator in cases where internal standardization is unavailable. For example, this method can be applied to calculate element (metal and metalloid) concentrations in carbonic (C–O–H) fluid inclusions and bubbles. The method is devoted to measuring incompatible (with the host mineral and glass) trace elements originally dissolved into the trapped fluid. The method requires precise estimation of the fluid density, the inclusion/bubble volume or average radius, and measurement of the laser ablation crater radius by independent microanalytical techniques as well as accurate data on the concentration of major/minor elements compatible with the host mineral (or host glass). This method, applicable for analyses of hydrous carbonic fluid inclusions and gas bubbles hosted in silicate minerals and glasses, relies on the absence of a matrix effect between fluid, host mineral and daughter phases (silicate, oxide or sulfide) and the external calibrator (e.g., reference silicate glasses) during the LA-ICP-MS analysis, an assumption validated by the use of femtosecond lasers.

Metal-Selective Processing from the Los Sulfatos Porphyry-Type Deposit in Chile: Co, Au, and Re Recovery Workflows Based on Advanced Geochemical Characterization

Sulfides extracted from porphyry-type deposits can contain a number of metals critical for the global energy transition, e.g., Co and precious metals such as Au and Re. These metals are currently determined on composite mineral samples, which commonly results in their dilution. Thus, it is possible that some metals of interest are overlooked during metallurgical processing and are subsequently lost to tailings. Here, an advanced geochemical characterization is implemented directly on metal-bearing sulfides, determining the grade of each targeted trace metal and recognizing its specific host mineral. Results show that pyrite is a prime host mineral for Co (up to 24,000 ppm) and commonly contains Au (up to 5 ppm), while molybdenite contains high grades of Re (up to 514 ppm) and Au (up to 31 ppm). Both minerals represent around 0.2% of the mineralized samples. The dataset is used to evaluate the possibility of extracting trace metals as by-products during Cu-sulfide processing, by the addition of unit operations to conventional plant designs. A remarkable advantage of the proposed workflows is that costs of mining, crushing, and grinding stages are accounted for in the copper production investments. The proposed geochemical characterization can be applied to other porphyry-type operations to improve the metallic benefits from a single deposit.

Amphibole lamellae formation in the upper mantle due to interaction of fluid inclusions and host minerals: a case study from Persani Mountains Volcanic Field, Transylvania

<p>Amphibole is one of the most abundant ’water’-bearing minerals in the Earth’s upper mantle. Amphiboles occur as interstitial grains, lamellae within pyroxenes or as daughter minerals within fluid inclusions.  Most commonly amphibole formation is related to mantle metasomatism, where the agent has a subducted slab (e.g. Manning 2004) or an asthenospheric origin (e.g. Berkesi et al. 2019).  After the formation of fluid inclusions, a subsolidus interaction can take place where the H<sub>2</sub>O content of fluid inclusions may crystallize pargasite (e.g. Plank et al. 2016).</p><p>Here we present amphibole lamellae formation in mantle xenoliths from the Persani Mountains Volcanic Field that is interrelated to a reaction between fluid inclusions and host clinopyroxene.  Newly formed amphibole lamellae occur only in the surroundings of the fluid inclusions and grow within the host clinopyroxene in a preferred crystallographic direction.  Studied lamellae do not reach the rim of the host mineral implying that components needed for formation of amphibole lamellae in clinopyroxene could have only originated from the fluid inclusion itself.  We measured the major element composition of amphibole lamellae and host clinopyroxene (1) and used Raman spectroscopy and FIB-SEM on fluid inclusion study situated next to the lamellae (2).  Results support the hypothesis that chemical components (dominantly H<sup>+</sup>) migrated sub-solidus from the fluid inclusion into the host mineral after fluid entrapment via subsolidus interaction.  Beyond the clinopyroxene-hosted fluid inclusions, fluid inclusions in orthopyroxenes were also studied as a reference.  Our study shows that post-entrapment diffusion from a fluid inclusion into the host mineral changes the solid/fluid ratio of the mantle  which could modify the rheology of the lithospheric mantle.</p><p>Berkesi, M. et al. 2019. Chemical Geology, 508, 182-196.</p><p>Kovács et al. (2017) Acta Geodaetica et Geophysica, 52(2), 183-204.</p><p>Manning C. E. 2004. Earth and Planetary Science Letters, 223, 1-16.</p><p>Plank, T. A. et al. 2016. In AGU Fall Meeting Abstracts.</p>

High Sensitivity Mapping of Melt Inclusions in Miocene Zircons of Central Anatolian Volcanic Province (CAVP), Cappadocia, Turkey

<p>Melt inclusions originate from small juvenile melt droplets trapped at magmatic pressures and temperatures during crystallization of their host mineral. Thus, melt inclusions retained by their host crystals can uniquely preserve evidence for the thermochemical conditions in the magma during crystal growth. Zircon is a resistant mineral even under magmatic conditions, and it is common in many different rock types (igneous, metamorphic, and sedimentary). Moreover, zircon crystallization significantly affects trace element concentrations of the melt during processes such as fractionation, melt separation, and/or retention of accessory phases in the residual melt. Its potential as a host mineral for melt inclusions, however, has not been fully realized, mainly because of the small size of zircon and its inclusions.</p><p>Here, we developed a new technique for ion imaging of elemental distributions in melt inclusions in zircon, and applied it to melt-inclusion bearing zircon crystals from selected Miocene ignimbrites of the Central Anatolian Volcanic Province, Turkey. The high-sensitivity ion imaging of zircon provides information about the 2-D distribution of critical elements in the crystal and its inclusions, and element distributions can be directly compared to cathodoluminescence (CL) patterns of the host. High-sensitivity element maps were obtained using a CAMECA 1280-HR IMS at Heidelberg University for areas of 25×25 µm at 2-3 µm lateral resolution. Ion images for each element containing 128×128 pixels raw intensity values were initially processed using instrumental software (WINImage©) to accumulate data from measurement cycles into a single image data. Each element map was then recorded as a grayscale image with intensities encoded in each pixel. The raster images for each element was further processed using ImageJ© and ARCGIS© programs, where each element map was converted to a color scale expressing the appropriate value ranges and the data obtained on the same trace element for each zircon in different units were reduced to the same legend values. The color ion images obtained from the grayscale images of each map were overlaid onto CL images to correlate trace element abundances with growth regions visible in CL images.</p><p>Imaging has the important advantage compared to spot analyses of melt inclusions that contamination from the wall of the host mineral can be mitigated. For this, Zr ion images were used as controls for selecting ROIs (Regions of Interest) in order to eliminate pixels with mixed signals at the interface between zircon and the inclusion due to the finite width of the ion beam. High resolution imaging of melt inclusions and zircon allowed re-evaluating zircon-melt partitioning behavior of important trace elements for natural melt compositions. Partitioning values for elements with comparatively low abundances in the melt relative to zircon (Y, Th, U and Dy) are slightly lower than spot analyses and previously published results but they all follow a similar trend with predicted partitioning coefficients. </p><p>This research was financed by The Scientific and Technological Research Council of Turkey within the research program number of 2214/A. </p>

The Experimental Research on the Separation for Floatation of the Sulfur and Arsenic in a Refractory Gold Ore

The ore belongs to a kind of refractory gold ore cotaining arsenic and high-sulfur, contains high-sulfur and low-gold, and arsenopyrite is the main host mineral for Au. Because the floating gold fine with arsenic from sulfur floatation. lead to high content of arsenic in sulfur concentrate. This part of the gold loss in the sulfur concentrate. By optimizing the structure of floatation flow and using the new inhabitor LY100 for arsenic, the indexes of small-scale closed circuit test were obtained: the sulfur concentrate grading at 48.78% with a recovery of 44.76% and with As 0.47%, the arsenic concertrate grading at 15.95% with a recovery of 75.14%.