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New U–Th–Pb chemical data from both electron probe microanalysis and U–Pb laser ablation-inductively coupled plasma mass spectrometry on monazite inclusions in giant andalusite porphyroblasts indicate that the lowermost subdivision of the Rocky Cape Group in northwest Tasmania underwent metamorphism at ca 1100 Ma. The Proterozoic Rocky Cape Group is a ∼10 km-thick succession of quartz arenite, siltstone and pelite. These sediments were deposited between ca 1450 and ca 1010 Ma. Metamorphism within the Rocky Cape Group ranges from the prehnite–pumpellyite to upper greenschist facies, locally reaching garnet grade. In the lowermost formation of the Rocky Cape Group, andalusite-bearing mineral assemblages in the Pedder River Siltstone formed prior to or synchronously with monazite development. The andalusite-bearing mineral assemblage indicates relatively low-pressure conditions of <200 MPa, consistent with the stratigraphic thickness of the Rocky Cape Group (∼10 km). However, the presence of the intermediate-temperature biotite–andalusite mineral assemblages (500 °C) in the study area suggests the contribution of additional heat sources. Garnet porphyroblasts were observed ∼2 km away. Similar-age medium-grade metamorphism and magmatism at about 1100 Ma have been observed regionally in the South Tasman Rise and East Tasman Plateau, and in areas that are thought to have been contiguous with northwestern Tasmania such as Dronning Maud Land, central Arizona (Yavapai–Mazatzal) and Belt–Purcell Basin in the southwestern and northwestern Laurentian crustal sequences. The pressure and temperature relationships, mineral associations and regional data suggest additional heat flow was present through the lower part of the Rocky Cape Group. The higher geothermal gradient could be attributed to burial during basin development and deposition of the upper Rocky Cape Group or associated magmatism on the margin of Laurentia during assembly of Rodinia. Low-pressure, intermediate-temperature mineral associations occur in the Rocky Cape Group. Heat sources are unrelated to nearby Devonian granite. Robust ages reveal the first discovery of 1100 Ma metamorphism in Tasmania. These provide data for a missing link in Rodinian paleogeographic reconstructions. [ABSTRACT FROM AUTHOR]

In this article, dumortierite from Croatia is described for the first time. Dumortierite formed in a pegmatite dyke cutting through Cretaceous two-mica leucogranite of the magmatic-metamorphic complex of Mt. Moslavačka Gora. The pegmatite dyke shows a magmatic mineral association of coarse-grained quartz, orthoclase, microcline and albite, less abundant muscovite, biotite, pinkish andalusite and blue-coloured prismatic dumortierite I crystals. Subsequent alteration by titanium-rich hydrothermal fluids led to partial replacement of dumortierite I and andalusite by secondary fibrous to acicular purple dumortierite II enriched in Mg and Ti. During temperature decrease perthite developed in feldspars and at a still later stage, sericite partially replaced not only feldspars but also andalusite and both types of dumortierite along grain boundaries and cracks. Final alteration at very low temperatures caused formation of clay minerals at the expense of feldspars. According to mineral chemical analyses, the feldspars are represented by albite and K-feldspar with a low albite component. Biotite corresponds to annite and its subhedral shape and chemical composition point to magmatic crystallisation from a peraluminous melt derived from a crustal source. Coarse muscovite flakes contain 1.31-1.48 wt.% FeO and 0.56-0.70 wt.% TiO2. Their Na/(Na+K) ratios (0.08-0.09) prove a magmatic origin, whereas lower ratios in sericite (0.04-0.06) indicate formation during retrogression. Magmatic muscovite is in textural equilibrium with andalusite, also implying an igneous origin for the latter, which belongs to the S3 textural type of andalusite in felsic igneous rocks. Electron microprobe analyses clearly show a strong positive correlation between Si tetrahedral deficiency (3-Si) and the sum of Al+Ti, (R²= 0.85) in both types of dumortierite, implying Al replacement by Ti. However, Al replacement by Ti is not restricted to Al in the octahedral position, as generally accepted, but most probably also in the tetrahedral position. Distinct pleochroic colours in dumortierite are usually explained by the [Fe/(Fe+Ti)]x100 factor, but according to this study, elevated Mg contents stabilize red to violet coloured dumortierite at higher [Fe/(Fe+Ti)] x100 factors than those previously suggested. Dumortierite-bearing pegmatite and host two-mica leucogranite show strong chemical similarities in their major, minor and trace element contents. Both rock types have a strong peraluminous character (ASI = 1.6 in pegmatite vs 1.8 in leucogranite), low CaO/Na2O ratios (0.11 vs 0.14), high Rb/Ba (74.5 vs 16.4) and Rb/Sr ratios (78.4 vs 43.3) as well as relatively high Al2O3/TiO2 ratios (261 vs 210). For the leucogranitic melt these characteristics indicate derivation from a pelitic source and low melting rates at relatively low temperatures. With respect to the field relationships and the chemical similarities, formation of the pegmatitic melt by fractional crystallisation during solidification of the two-mica leucogranite is inferred. Based on the mineralogical composition, the dumortierite-bearing pegmatite from Mt. Moslavačka Gora may be a member of the abyssal pegmatite class and the AB-BBe subclass. However, its formation by fractional crystallisation from a granitic melt argues against this interpretation, as all other dumortierite-bearing granitic pegmatites occur in high-grade metamorphic host rocks and are thought to be products of anatectic melting of country rocks. Therefore, the investigated pegmatite is quite unique and not fully comparable with any previously described dumortierite-bearing pegmatite worldwide. [ABSTRACT FROM AUTHOR]

Fe- and Al-rich metapelite from the Transangarian segment of the Yenisey Ridge (East Siberia, Russia) is a potential new source of high-alumina refractories. The rocks have relatively high average contents of Al2O3 (20 wt%) and Fe2O3 (7.91 wt%), moderate K2O (3.44 wt%), and low CaO (0.74 wt%). Their dominant mineral assemblages are andalusite + muscovite + margarite + chlorite + biotite + quartz or staurolite + kyanite or/and andalusite + chlorite + muscovite + biotite + quartz with ±garnet and ±plagioclase. Al2SiO5 polymorphs occur as up to 1.5 cm andalusite porphyroblasts and partial or complete pseudomorphs after andalusite (kyanite and staurolite). Accessories include abundant Fe–Ti oxides and sporadic REE-, Y-, Ca-phosphates; sulfides are negligible. The composition of Al2SiO5 concentrates obtained in laboratory by heavy-media and magnetic separation from ≥0.06 mm fractions meet all requirements for raw material of this type: >56 wt% Al2O3, <42 wt% SiO2, <1 wt% Fe2O3, <1.2 wt% TiO2, and <0.2 wt% (CaO + MgO). The andalusite, kyanite, and mixed ores yield 0.7–4.1 wt%, 0.7–2.2 wt%, and 1.9–6.0 wt% of concentrate, respectively. The best-quality ores rich in Al2SiO5 polymorphs reside in zones of contact and/or dynamic metamorphism superimposed over regional metamorphism of Al-rich rocks. [ABSTRACT FROM AUTHOR]

The main problem affecting the life of refractory linings in furnaces is alkaline corrosion formed during biomass combustion, especially in systems with SiO2–Al2O3. This corrosion effect is very intensive compared to using conventional technologies designed for burning traditional fuels. This study focuses on the development of a new type of andalusite refractory material with a higher corrosion resistance to K2CO3 and fly ash after biomass combustion. The original andalusite refractory material is labeled A60PT0, with an oxide content of 60 wt.% Al2O3 and 37 wt.% SiO2, a compressive strength parameter of 64 MPa, and an apparent porosity of 15%. In the experiment, four mixtures (labeled A60PT1–A60PT4) were modified primarily using the raw materials and granulometry. The fly ash was characterized by an X-ray diffraction analysis with the following phases: quartz, calcite, microcline, leucite, portlandite, and hematite. According to the X-ray fluorescence analysis, the samples contained the following oxides: 47 wt.% CaO, 12 wt.% K2O, 4.6 wt.% SiO2, 3.5 wt.% MgO, and some minority oxides such as P2O5, MgO, MnO, and Fe2O3 between 2 and 5 %. The tendency for slagging/fouling of the ash was determined with the help of the indexes B/A, TA, Kt, and Fu. The final material was a shaped andalusite refractory material labeled A60PT4 with a content of 65 wt.% Al2O3 and 36 wt.% SiO2. The properties of the andalusite material were a compressive strength of 106.9 MPa, an apparent porosity of 13%, and the recommended temperature of use up to 1300 °C. For corrosion testing, a static crucible test was performed according to the norm ČSN CEN/TS 15418 and the company's internal regulation. The exposure time of the samples was 2 h and 5 h at temperatures of 1100 °C and 1400 °C for K2CO3 and ash, respectively. For the evaluation of tested samples, an X-ray powder differential analysis, an X-ray fluorescence analysis, scanning electron microscopy, and energy-dispersive X-ray spectroscopy were used. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fe- and Al-rich metapelite from the Transangarian segment of the Yenisey Ridge (East Siberia, Russia) is a potential new source of high-alumina refractories. The rocks have relatively high average contents of Al2O3 (20 wt%) and Fe2O3 (7.91 wt%), moderate K2O (3.44 wt%), and low CaO (0.74 wt%). Their dominant mineral assemblages are andalusite + muscovite + margarite + chlorite + biotite + quartz or staurolite + kyanite or/and andalusite + chlorite + muscovite + biotite + quartz with ±garnet and ±plagioclase. Al2SiO5 polymorphs occur as up to 1.5 cm andalusite porphyroblasts and partial or complete pseudomorphs after andalusite (kyanite and staurolite). Accessories include abundant Fe–Ti oxides and sporadic REE-, Y-, Ca-phosphates; sulfides are negligible. The composition of Al2SiO5 concentrates obtained in laboratory by heavy-media and magnetic separation from ≥0.06 mm fractions meet all requirements for raw material of this type: >56 wt% Al2O3, 2, 2O3, 2, and 2SiO5 polymorphs reside in zones of contact and/or dynamic metamorphism superimposed over regional metamorphism of Al-rich rocks.

Gorundum-mullite materials were prepared with homogeneous bauxite chamotte, andalusite fine powder, Guangxi white clay as raw materials firing at 1 400 °C for 4 h. The effect of the andalusite fine powder addition (0,5%,10%,and 15%,by mass) on their properties such as the density, the strength, the refractoriness under load, the thermal shock resistance, the hot creep resistance was studied. The results show that: (1) with the increase of the andalusite fine powder addition, the bulk density of the samples gradually decreases, the thermal shock resistance and the hot creep resistance gradually enhance, the refractoriness under load gradually rises, and the cold crushing strength basically remains unchanged; the sample added with 15% of andalusite has the best comprehensive performance; (2)after firing at 1 400 °C for 4 h,the surface layer of andalusite fine powder particles shows complete mullitization,and the mullitization degree gradually decreases from the surface to the inside, which enables further mullitization during subsequent high-temperature heating, thus playing a positive role to the thermal shock resistance, the hot creep resistance and the refractoriness under load of the materials. [ABSTRACT FROM AUTHOR]

Our previous research showed that the addition of andalusite aggregates can enhance the oxidation resistance of Al2O3‐SiC‐C castables; this is attributed to the transformation of andalusite into a silica‐rich glass phase that blocks pores. Theoretically, andalusite with a smaller particle size would achieve a higher extent of conversion and generate more silica‐rich glass, which would be more conducive to blocking pores. Therefore, this study evaluates the influence of andalusite fine powder on the oxidation resistance of Al2O3‐SiC‐C castables containing a reduced amount of Si antioxidant. The results show that introducing a small amount of andalusite fine powder endows the Al2O3‐SiC‐C castables with significant oxidation resistance so that the traditional addition of Si metal as an antioxidant can be substantially reduced or even completely eliminated. Meanwhile, the thermal shock stability and strength of the castables were also enhanced. [ABSTRACT FROM AUTHOR]

The present work aims to prepare mullite‐based ceramics at low temperature mainly from andalusite and marble byproduct by a solid‐state interaction method. Marble powder byproduct was used, in the prospect of waste management, as a sintering aid. The influence of marble powder byproduct (5 wt.%) on the phase formation, microstructure‐temperature evolution, densification, and mechanical strength was evaluated by means of XRD, TGA‐DTA, and SEM. The results revealed that the andalusite remained present with mullite up to 1400°C, while the addition of 5 wt.% of marble byproduct involved its complete transformation into mullite and a trace of anorthite. The transformation of andalusite into mullite upon the heating in the range 1300–1400°C involved the densification of the matrix body and a significant increase in mechanical strength from 60 to 170 MPa, which promoted its application for refractory materials. [ABSTRACT FROM AUTHOR]

Syn-tectonic quartz veins are widely present in low- to medium-grade metapelitic belts, however, dating these veins is challenging due to the lack of suitable target minerals for most geochronological methods. Andalusite is a common K-poor aluminosilicate mineral in these quartz veins. In this study, we demonstrate the feasibility of dating fluid inclusions in andalusite using the 40Ar/39Ar gentle stepwise crushing technique. Three andalusite samples in syn-tectonic quartz veins from the Chinese Altai, Central Asia yielded similar gas release patterns. The first crushing steps generated significant excess 40Ar which likely originated from secondary gas inclusions. These steps gave anomalously old and quickly declining apparent ages. The following crushing steps generated less significant excess 40Ar and yielded concordant and well-defined Early Permian ages of 282–277 Ma. These steps were likely dominated by the degassing of intra-crystal liquid-rich fluid inclusion planes. Two of the crushed powder samples from the stepwise crushing experiments were selected for additional 40Ar/39Ar stepwise heating using a furnace and yielded a much younger age of 216 Ma. Laser stepwise heating of muscovite flakes in two of the investigated andalusite samples and one chloridized biotite sample from a different andalusite-bearing quartz vein yielded 40Ar/39Ar ages of 243–241 Ma and 214 Ma, respectively. Compared with gases released from the crushing experiments, gases extracted from the heating experiments showed distinct Cl–K–Ca compositional characteristics and younger ages with near atmospheric initial 40Ar/36Ar value. These observations suggest that 1) contrary to common wisdom, excess 40Ar in K-poor nesosilicates are preferably preserved in fluid inclusions rather than mineral lattices, and 2) K (Ar) contamination from K-bearing solid phases is negligible during gentle stepwise crushing. As such, the 282–277 Ma fluid inclusion 40Ar/39Ar ages could be considered as the timing of andalusite growth in the quartz veins. The younger muscovite 40Ar/39Ar ages likely record more recent cooling events. The youngest 40Ar/39Ar ages of the crushed andalusite powder and the biotite sample could reflect the timing of sericitization and chloritization of the samples, which is evidenced by petrologic observations and x-ray K mapping results. Furthermore, andalusite 40Ar/39Ar ages agree with the monazite/zircon U–Pb ages (280–273 Ma) of syn-tectonic leucogranite and pegmatite dykes and metamorphic ages (299–262 Ma) for the low-pressure metamorphic rocks of the region. These results suggest that fluid inclusion 40Ar/39Ar geochronology of andalusite can be used to constrain the timing of deformation and associated metamorphism in low-pressure metapelitic terranes, which can also provide more complete pictures of the tectono-thermal evolution in combination with traditional 40Ar/39Ar stepwise heating geochronology. [ABSTRACT FROM AUTHOR]

Detailed microstructural, microfabric and chemical analyses of felsic granulite within and around a ductile shear zone at the Plešovice quarry in the southern Bohemian Massif revealed deformation-induced, retrograde transformation of kyanite to andalusite. Although andalusite is absent outside the shear zone, its fraction among Al 2 SiO 5 polymorphs significantly increases up to ∼59% inside the shear zone, while the fraction of kyanite significantly decreases from ∼98% outside the shear zone down to ∼22% inside the shear zone. Three examples of andalusite and the relict kyanite pair suggest a common topotaxial relationship such that andalusite (010) is parallel to the precursory kyanite (100), while andalusite [100] and [001] are parallel to the precursory kyanite [010] and [001], respectively, indicating that the growth of andalusite was crystallographically controlled by the precursory kyanite. The felsic granulite in the ductile shear zone at the Plešovice quarry has been repeatedly subjected to brittle shearing accompanied by pseudotachylite formation and plastic shearing with mylonitization, suggesting development of the ductile shear zone at the brittle–plastic transition zone. Mylonitization of the felsic granulite was promoted by deformation-induced K-feldspar replacement by myrmekite at temperatures of 390–440 °C assuming a pressure of 250 MPa. • Deformation-induced, retrograde transformation of kyanite to andalusite revealed. • Andalusite growth was crystallographically controlled by the precursory kyanite. • Transformation occurred at temperatures of 390–440 °C assuming a pressure of 250 MPa. [ABSTRACT FROM AUTHOR]

The main problem affecting the life of refractory linings in furnaces is alkaline corrosion formed during biomass combustion, especially in systems with SiO2–Al2O3. This corrosion effect is very intensive compared to using conventional technologies designed for burning traditional fuels. This study focuses on the development of a new type of andalusite refractory material with a higher corrosion resistance to K2CO3 and fly ash after biomass combustion. The original andalusite refractory material is labeled A60PT0, with an oxide content of 60 wt.% Al2O3 and 37 wt.% SiO2, a compressive strength parameter of 64 MPa, and an apparent porosity of 15%. In the experiment, four mixtures (labeled A60PT1–A60PT4) were modified primarily using the raw materials and granulometry. The fly ash was characterized by an X-ray diffraction analysis with the following phases: quartz, calcite, microcline, leucite, portlandite, and hematite. According to the X-ray fluorescence analysis, the samples contained the following oxides: 47 wt.% CaO, 12 wt.% K2O, 4.6 wt.% SiO2, 3.5 wt.% MgO, and some minority oxides such as P2O5, MgO, MnO, and Fe2O3 between 2 and 5 %. The tendency for slagging/fouling of the ash was determined with the help of the indexes B/A, TA, Kt, and Fu. The final material was a shaped andalusite refractory material labeled A60PT4 with a content of 65 wt.% Al2O3 and 36 wt.% SiO2. The properties of the andalusite material were a compressive strength of 106.9 MPa, an apparent porosity of 13%, and the recommended temperature of use up to 1300 °C. For corrosion testing, a static crucible test was performed according to the norm ČSN CEN/TS 15418 and the company’s internal regulation. The exposure time of the samples was 2 h and 5 h at temperatures of 1100 °C and 1400 °C for K2CO3 and ash, respectively. For the evaluation of tested samples, an X-ray powder differential analysis, an X-ray fluorescence analysis, scanning electron microscopy, and energy-dispersive X-ray spectroscopy were used.

The high content of the AAEMs in Zhundong (ZD) coal causes easily slagging on the heating surface of boilers, and the addition of rice husk hydrochar (RHC) is expected to alleviate slagging by introducing SiO2 content. ZD coal is co‐fired with RHC according to different blend ratios, co‐combustion ashes are prepared subsequently at different temperatures. The co‐combustion characteristics of blends are studied firstly by using TGA, considering the combustion process can bring impacts on ash characteristics. Then the effects of the blend ratio and ashing temperature on the ash characteristics are discussed. The ash samples are characterized by XRF, ICP‐AES, XRD and SEM. The results show that an increase in the blend ratio of the RHC reduces the ignition temperature and lengthens the burnout time, which transforms the ash characteristics. The contents of quartz, gehlenite and andalusite greatly increase. The number of fine particles in the ash decreases, while the particle size increases. The ash fusion temperatures (AFTs) are at the lowest value at 8:2 and exceed totally that of ZD coal at 7:3. Considering to increase the AFTs of ZD coal, at least the blend ratio of 7:3 of ZD coal and RHC is recommended for co‐combustion. [ABSTRACT FROM AUTHOR]

In our previous study, high amounts of andalusite aggregates (about 19%) were used to improve the oxidation resistance of Al2O3-SiC-C castables, attributed to the transformation of andalusite. However, for andalusite aggregates with large particle size, only a small part of the silica-rich glass phase (about 20%) is extruded onto the surface of the particles to block the pores. Theoretically, the smaller particle size promotes the conversion of andalusite, and more silica-rich glass phase would be extruded to the particle surface to block the pores in the castables, which is speculated to favor the enhancement of the oxidation resistance of the castables. Therefore, in this work, andalusite fine powder (<0.055 mm) was employed to substitute the same-weight proportion of fused brown corundum fine powder in the castables. The results demonstrate that a small amount of andalusite fine powder can achieve the similar antioxidation enhancement compared with high addition content of andalusite aggregate. And the properties of castables fired at different temperatures proved that the thermal decomposition of andalusite fine powder into silica-rich glass and mullite is the key reason of elevated oxidation resistance as well as the improvement of strength and thermal shock stability. [ABSTRACT FROM AUTHOR]

This work deals with the chemical, physical, thermal and mechanical characterization of andalusite rich schist from Oulmes area (Central Morocco) for potential application in traditional ceramics. A homogeneous powder was sintered up to 1200 °C and was evaluated for their possible ceramic applications. Thermal analysis (TG), X-ray diffraction (XRD), scanning electron microscopy (SEM) and physical-mechanical analyses (bending strength, water absorption and bulk density) were used to assess the thermal behavior, phase evolution and microstructure of the fired mixtures. The formations of the anorthite and mullite beside andalusite and vitreous phase have improved the final technological specifications required by the European Normative reference (EN 14411) for ceramic products. Our results indicated ceramics belong to the BIII group at 1100 °C and BIIb at 1200 °C which are suitable for the production of cottoforte and majolica materials respectively.

In order to verify the thermal expansion behaviour of andalusite aggregates with different mullitization degrees and its influence on the properties (thermal shock resistance and especially volume stability) of mullite-corundum refractories, the properties of mullite-corundum refractories with uncalcined and different pre-calcined andalusite aggregates (1–3 mm) are investigated in terms of permanent liner change, thermal shock resistance, cold modulus of rupture, modulus of elasticity and apparent porosity. The experimental results show the volume stability of samples increases when the pre-calcining temperature of andalusite is improved (1300–1500 °C), as less residual andalusite in the pre-calcined aggregates leads to smaller volume expansion in the refractory samples during firing at high temperatures. Meanwhile, mullite-corundum refractories with andalusite aggregates (1–3 mm) pre-calcined at higher temperature have better cold modulus of rupture, because the increase of pre-calcining temperature could promote mullization degree and thereby bring down the length of microcracks and also enhance the densification of these as-prepared refractories. Moreover, mullite-corundum refractories with uncalcined and pre-calcined andalusite aggregates present good thermal shock resistance; the corresponding residual strength ratio of mullite-corundum refractories containing 1500 °C or 1600 °C pre-calcined andalusite aggregates is still higher than 90%. Overall, the volume stability and cold modulus of rupture of the mullite-corundum refractories could be significantly enhanced through the incorporation of 1500 °C pre-calcined andalusite aggregates (1–3 mm), and all mullite-corundum refractories with uncalcined and pre-calcined andalusite aggregates (1–3 mm) exhibit good thermal shock resistance. [ABSTRACT FROM AUTHOR]

Copyright of Geologia USP: Série Científica is the property of Geologia USP and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: This paper compares the thermal shock damage resistance and the slag corrosion resistance of a high-alumina and an alumina-containing andalusite refractory castable. Thermal shock damage resistance was analyzed through thermal cycling and thermal shock damage resistance parameters. Thermal shock cycling damage was analyzed using the dynamic modulus of elasticity (E) and the modulus of rupture (MOR) before and after the thermal shock cycles. The alumina-containing andalusite castable showed superior thermal shock damage resistance in both parameters. The high-alumina castable showed a higher resistance to slag corrosion. These results were linked to material selection for specific industry applications. [ABSTRACT FROM AUTHOR]

The northernmost part of the Australian continent is exposed in a basement high in the Bird's Head Peninsula at the NW tip of New Guinea. This basement consists of Silurian–Devonian turbidites that were regionally metamorphosed in the lower greenschist facies. Along its eastern margin, the basement high is intruded by numerous granitoid bodies and records a second, higher‐grade metamorphic overprint. We present the first detailed study of metamorphic rocks from this eastern part of the basement high, supported by field and petrographic observations, bulk rock and mineral chemistry, and phase equilibria modelling. Lower‐grade basement rocks include chlorite‐mica schists, slates, silt‐, and sandstones, which give way to andalusite‐ and cordierite‐bearing pelites and psammites, interspersed with layers of quartzite. The dominating pelitic phase assemblage is biotite+white mica±andalusite±cordierite+plagioclase+quartz+ilmenite; incipient sillimanite (fibrolite) is present in some rocks and replaces andalusite in baked margins around the numerous dykes and sills. Other rock types include metasedimentary migmatites, metacarbonates and calcsilicate concretions, rare metavolcanics, and kyanite‐bearing segregation veins. Metamorphism is of regional extent and often unrelated to granitoid intrusions. Our observations support the previous notion of an increase in peak metamorphic temperature from west to east. Microstructural relations suggest two phases of metamorphism, which are tentatively correlated with two phases of magmatic activity in the Devonian–Carboniferous and the Permian–Triassic. Based on petrographic observations and phase equilibria modelling, we propose that during the Permian–Triassic, metamorphism proceeded under high temperature/low pressure (HT/LP) or Abukuma‐type conditions along a narrow, counter‐clockwise P–T–t path with peak metamorphic conditions of the amphibolite facies (~520–650°C and ~2–4 kbar), potentially in an active continental margin setting. While much less evidence is available, similar metamorphic conditions are proposed for the Devonian–Carboniferous metamorphic event. [ABSTRACT FROM AUTHOR]

Our work previously found that the addition of andalusite aggregate enhanced the oxidation resistance of Al 2 O 3 –SiC–C castable. Therefore, it is speculated that the addition of andalusite can reduce the dosage of anti-oxidant. In this work, decreasing amounts of anti-oxidant Si (1.5 wt% - 0 wt%) are employed to further reveal the influence of andalusite aggregate on the oxidation resistance of Al 2 O 3 –SiC–C castable. The oxidation resistance of the specimens is evaluated by the oxidation index after the thermal shock resistance test. The phases composition of the castables were characterized via XRD, and its microstructures were tested via SEM. The Al 2 O 3 –SiC–C castables containing andalusite aggregate and reduced amount of antioxidant Si demonstrate better oxidation resistance as the SiO 2 -rich liquid glass from andalusite transformation enters the pores under capillary force, blocks the pore channels and thus prevents the inward diffusion of oxygen. Additionally, partial silica-rich liquid glass produced by the converted andalusite particle would have a reaction with Al 2 O 3 in the castables to form secondary mullite, contributing to a denser structure, which is also conducive to blocking oxygen entry and consequently improving the oxidation resistance of the castables. [ABSTRACT FROM AUTHOR]

Adsorption of lead(II) as a major heavy metal pollutant onto nano-adsorbents of Andalusite, Kyanite and Sillimanite was studied in a batch system. Nano­-adsorbents were prepared via crushing, using a planetary ball mill and then characterized by different analyses such as: SEM, XRD, XRF and FT-IR. Major factors affecting the adsorption process were studied including pH, adsorbents dosage, initial metal concentration and temperature. Afterward, the adsorption process was studied isothermally, kinetically, and thermodynamically. The results show that aluminum silicates polymorphs are efficient adsorbents for removal of lead(II) and the removal exceeds 90%. The Freundlich isotherm model was best fitted with the experimental data. Chemisorption may control the rate of adsorption due to following the pseudo-second-order kinetic model. Thermodynamic investigation proved low randomness, exothermic and spontaneous nature of the process.

Chiastolite-type andalusite, whose genesis occurred in the currently unexploited deposit of Sidi Bou Othman (Morocco), has been extensively characterized. The phase composition, microstructure, thermal behavior, sinterability, and evolution of the crystallographic structure associated with the transformation of andalusite to mullite were accurately analyzed. Parallelepiped-shaped crystal grains exhibited off-white X crosses, typical of the chiastolite group. The chemical composition is closely dependent on the crystal size and proportion of alumina. The crystal structure was successfully refined using XRD, and chemical analysis was performed for different crystal sizes up to 30 mm. Powder compacts were prepared from these chiastolites for further characterization after various thermal treatments. According to the Rietveld refinement analysis, the mullization ranges from 1200 to about 1500 °C, and crystallographic parameters have been compared with other andalusites reported in literature. In agreement with this phase transformation, variations related to different material properties such as thermal expansion, pore volume fraction, and mechanical strength were evaluated. These results highlight the potential for further exploitation of the Sidi Bou Othman deposit to produce refractory materials.

The study of flotation interaction between andalusite and quartz found that when the pH value is 8 and the dosage of FeCl$ * 6H2O is 20 mg/L and the dosage of sodium oleate is 150 mg/L? with the interaction distance between the andalusite and quartz particles is smaller，the negative value of the total E DLVO potential energy is larger ?indicating that the force of each grade of quartz and different grades of andalusite is attractive，and there is an adhesive cover between each other. Microscopic observations further verified that adhesion between andalusite and quartz did occur. The main effect form of the interactive effect of andalusite and quartz flotation is the mutual adhesion cover between minerals ? including fine grained quartz，it can adhere to coarse grained andalusite? which is represented by the slime cover?fine grained andalusite can adhere to coarse grained quartz，fine grained andalusite can adhere to and aggregate with fine grained quartz. In the sodium oleate system ? citric acid can be used to effectively weaken the adhesion and cover between quartz and andalusite. The better effect of citric acid on the separation of andalusite and quartz is concentrated at -- 106 + 45 ptm and -- 45 + 18 ptm. [ABSTRACT FROM AUTHOR]

In the present work, the effects of the pre-firing temperature of andalusite aggregates (5–3 mm) on the conversion of andalusite as well as the volume stability and oxidation resistance of the Al 2 O 3 –SiC–C castables were investigated. The phases of the andalusite aggregates were tested via X-ray diffraction, and their microstructures as well as those of the castables were characterized via scanning electron microscopy. The linear expansion of the castables decreased with increase in the pre-firing temperature of andalusite, as less residual andalusite in the pre-fired aggregates lowered its transformation in the castables during firing at high temperatures. Moreover, the higher amounts of SiO 2 -rich glass produced by andalusite pre-fired at high temperatures and secondary mullite generated between andalusite and the matrixes were both favorable to the production of castables with denser structure. This prevented the diffusion of O 2 into the castables and improved their oxidation resistance. [ABSTRACT FROM AUTHOR]

High-temperature Raman spectra of natural sillimanite, andalusite and kyanite were measured in the temperature range of 296–1273 K at ambient pressure. No phase transition was observed over the temperature range in this study. Raman modes for the three samples vary with temperature linearly. The temperature and pressure dependence of the force constants for Si–O stretching vibrations in Al2SiO5 polymorphs were determined. The isobaric mode Grüneisen parameters of sillimanite, andalusite, and kyanite were determined from the temperature dependent of present high-temperature Raman spectra and previous results of thermal expansion coefficients. The intrinsic anharmonic mode parameters were estimated and nonzero, indicating the existence of intrinsic anharmonicity for sillimanite, andalusite and kyanite. Based on Kieffer model, the thermodynamic parameters, including isochoric heat capacity and entropy, were calculated. [ABSTRACT FROM AUTHOR]

This work investigates the effect of andalusite with different particle sizes (8-5 mm, 5-3 mm, 3-1 mm) on the properties of Al 2 O 3 –SiC–C castables. It has been found that the addition of andalusite aggregates not only improves high-temperature strength and thermal shock resistance of the materials, but additionally favors the oxidation resistance of the castables. The phases and microstructure of the castables were characterized by X-ray diffraction and scanning electron microscopy, respectively. The microstructural observation suggests that the enhanced oxidation resistance of Al 2 O 3 –SiC–C castables with andalusite aggregates addition results from the obstruction of the pore channel and improved densification of the castables caused by andalusite mullitization, which prevent oxygen diffusion inside the castables. [ABSTRACT FROM AUTHOR]

The separation of andalusite and quartz was investigated in the sodium oleate flotation system, and its mechanism was studied by solution chemical calculation, zeta-potential tests, Fourier transform infrared spectroscopic (FTIR), and X-ray photoelectron spectroscopic (XPS). The flotation tests results show that FeCl3·6H2O has a strong activation effect on andalusite and quartz and citric acid has a strong inhibitory effect on activated quartz, thus increasing the floatability difference between quartz and andalusite when the pulp pH is approximately 8. The FTIR, Zeta potential, and XPS analyses combined with the chemical calculation of flotation reagent solutions demonstrate that Fe forms hydroxide precipitates on the surface of andalusite and quartz and that oleate anions and metal ions adsorb onto the surface of the minerals. The elements Al and Fe can be chemically reacted. The anions in citric acid have different degrees of dissolution of Fe on the andalusite and quartz surfaces, thereby selectively eliminating the activation of the elemental Fe on andalusite and quartz and increasing the floatability of andalusite, leading to a better separation effect between andalusite and quartz. [ABSTRACT FROM AUTHOR]

The conventional refractory sagger materials, e.g., mullite, cordierite, and magnesium aluminum spinel, employed to calcine Li-ion battery (LIB) cathode materials, are easily attacked by the LIB material and thus have short lifetimes. To improve the corrosion resistances of refractory saggers to LIB materials, andalusite–KAlSi 2 O 6 (KAS 4) materials with different contents of in-situ KAS 4 were synthesized using andalusite and KAS 4 precursor calcined at 1300 °C. The microstructure evolution, phase development, corrosion resistances to Li(Ni x Co y Mn z)O 2 (LNCM) cathode materials and thermomechanical properties of the designed andalusite-KAS 4 materials were characterized. The results show that the corrosion resistances of the prepared andalusite–KAS 4 material were superior to those of the LNCM materials owing to the in–situ KAS 4 wrapping andalusite grains. The prepared andalusite–corundum–KAS 4 materials also exhibited improved strengths and appropriate thermal shock resistances compared with mullite-based refractories. • Andalusite-KAS 4 -based material has superior corrosion resistance to Li(Ni x Co y Mn z)O materials. • KAS 4 was formed in situ around andalusite grains as protection layer. • Andalusite-KAS 4 -based material exhibited proper thermomechanical properties. [ABSTRACT FROM AUTHOR]

The matrix lightweight porous reticulated materials (matrix LPRMs) were fabricated with fly ash, alumina and andalusite by the polymer sponge replica technique. Further, the matrix LPRMs were immersed in recoated slurries for vacuum infiltrated process, followed by sintering at 1400 °C to obtain vacuum infiltrated lightweight porous reticulated materials (vacuum infiltrated LPRMs). The rheological behavior, microstructure, composition of phases and mechanical properties of the matrix LPRMs and vacuum infiltrated LPRMs were examined. The results confirmed that andalusite had a positive influence on the mechanical properties, microstructure and thermal shock stability of the lightweight porous reticulated materials. Finally, the effect of the amount of andalusite added on the residual stress of the lightweight porous reticulated material been studied by a calculated model. [ABSTRACT FROM AUTHOR]

Powder and single-crystal diffraction data measured from the three geologically important Al2SiO5 polymorphs, kyanite, andalusite and sillimanite, over the last six decades have given varying accounts of each polymorph's thermal expansion, the scatter between and even within experimental datasets often being quite large. Furthermore, there are no lattice parameter determinations below 273 K, where the thermodynamic functions vary substantially, and few measurements above 1200 K. Accurate and precise lattice parameters of natural kyanite, andalusite and sillimanite have therefore been obtained in the range 10–1573 K using the high-resolution powder diffractometer (HRPD) at the ISIS neutron spallation source. Accuracy is ensured by the use of an internal standard (NIST silicon SRM640c) and use of a bulk probe (neutrons) to avoid the specimen-displacement corrections required by typical back-reflection X-ray diffraction methods. Precision is ensured by use of the time-of-flight method on one of the longest primary neutron flightpath instruments in the world. For kyanite, the improved precision reveals the true temperature dependence of the three inter-axial angles for the first time, permitting derivation of accurate thermal expansion tensor coefficients. For both andalusite and sillimanite, the measurements reveal hitherto unknown regions of substantial negative linear expansivity below room temperature, along the c-axis in andalusite and along the a-axis in sillimanite. Above 1200 K, sillimanite exhibits an anomalous increase in thermal expansion that may be due to a change in the Al/Si tetrahedral site ordering. [ABSTRACT FROM AUTHOR]

Andalusite and kyanite are two polymorphic minerals with the same formula but different crystal structures. Despite of their high economic values, selectively recovering them by flotation is a challenge. The flotation recovery of andalusite is higher than that of kyanite with sodium oleate. Sodium oleate adsorbs onto the surfaces mainly through the chemical interaction of oleate ions with aluminum atoms. The higher adsorption of sodium oleate on andalusite surface between the two minerals is related to the higher chemical activity of the aluminum atoms which leads to the better affinity and therefore the lower adsorption energy of sodium oleate. [ABSTRACT FROM AUTHOR]

Pressure–temperature–time (P–T–t) estimates for the Montresor Belt, obtained using phase equilibria and geospeedometry modelling integrated with in situ U–Th–Pb monazite geochronology, shed new light on the tectonometamorphic effects of the Snowbird phase of the Trans-Hudson orogeny. Typical metapelitic assemblages of the lower Montresor group consist of white mica, biotite, plagioclase, quartz, and andalusite, which in some rocks is partly or completely pseudomorphed by white mica. The observed assemblages reflect peak P–T conditions centring at approximately 575 °C and 3 kbar. Rocks with high bulk Fe/Mg contents contain compositionally zoned garnet, permitting the addition of further constraints on the conditions of metamorphism in the Montresor Belt: Core compositions of earliest-grown garnets indicate initial garnet crystallization at approximately 535 °C and 2.3 kbar, suggesting a nearly isobaric P–T path of prograde metamorphism with a gradient of approximately 50 °C·kbar–1. Chemical age-dating of monazite inclusions in garnet yields ages of ca. 1870 ± 9 to 1837 ± 9 Ma. Retrograde, pseudomorphic andalusite replacement by white mica at approximately 540 °C is inferred to have been controlled by variations in bulk rock chemistry. Morphologically corroded and chemically heterogeneous monazite adjacent to white mica pseudomorphs suggests that andalusite replacement took place at ca. 1792 ± 10 Ma, possibly associated with extension and movement along the detachment fault separating the upper and lower Montresor groups. Simulations of diffusion across chlorite- and biotite-filled cracks in garnet assumed to be coeval with andalusite replacement suggest that the rocks have experienced the retrograde event for at least 20 My. [ABSTRACT FROM AUTHOR]

Migmatitic rocks in the Hamedan area, Sanandaj-Sirjan Zone, Iran, contain symplectite that has partially replaced andalusite. In metatexite, symplectite typically consists of spinel + cordierite + Ca-rich plagioclase ± orthoamphibole, but in diatexite, symplectite consists of spinel + Ca-rich plagioclase; cordierite is typically absent from symplectite although it is present in the matrix of the rock. A calculated P-T pseudosection for an average, nonmigmatitic bulk-rock composition indicates that the whole-rock composition was not the effective bulk composition during the formation of symplectite. Therefore, effective bulk compositions (EBCs) were calculated using modal abundance and the average composition of minerals in contact with Al2SiO5 in metatexite and diatexite. The EBC pseudosections predict a stability field for spinel + plagioclase ± cordierite in both types of migmatite and estimate peak conditions at ~740 °C, 4.3 kbar, the same results for peak P-T conditions obtained by the average, nonmigmatitic rock composition. P-XH2O diagrams calculated assuming different H2O contents indicate that the effect of additional H2O on reaction history could resemble the effect of decompression. The Simin spinel-bearing symplectite associated with andalusite is similar to other examples reported in the literature in that it contains Ca-rich plagioclase, although the Simin rocks lack other Ca-rich phases such as garnet. The role of migmatization, including the introduction of external melt, is therefore considered as a possible agent in the generation of Ca-rich plagioclase. Based on calculated pseudosections, migmatite of the Simin area of the Hamedan metamorphic sequence exhibits an anticlockwise P-T path, and its formation could be linked to that of the granitoid intrusion during the main plutonic phases in the middle Jurassic under hightemperature - low-pressure metamorphic conditions. [ABSTRACT FROM AUTHOR]

The reaction process of zircon (ZrSiO4) in the andalusite (Al2SiO5)-zirconia system was studied at the temperatures from 1270 to 1460 °C. Phase compositions and microstructures of reaction products were analyzed by X-ray diffraction analysis, scanning electron microscopy and energy-dispersive spectrometer. The results show that andalusite starts to react with ZrO2 to form zircon and mullite at 1270 °C. As the temperature rises, the amount of zircon gradually increases. The reaction process is in accordance with the nuclei and growth models: Amorphous silica formed by the decomposition of andalusite reacts with zirconia to form zircon crystal nucleus, and the nucleus continues to develop and encapsulate the ZrO2. Then, the amorphous silica reacts with zirconia through the product layer of zircon. The time exponent of m illustrates that the reaction between andalusite and zirconia is not an isokinetic process. The reaction rate constant increases with the rise of temperature. The activation energy of the reaction is 127.28 kJ mol−1. [ABSTRACT FROM AUTHOR]

Metapelitic migmatites in the Hamedan area of Sanandaj–Sirjan Zone, Iran, contain spinel + gedrite + cordierite (± biotite, ± staurolite, ± ilmenite) symplectite, replacing andalusite in metatexite and diatexite. P-T conditions of metamorphism for cordierite-hornfels, andalusite-cordierite-hornfels and migmatites were estimated as 600°C, 2.2 kbar; 645°C, 2.9 kbar and 760°C, 3.7 kbar respectively, using calculated pseudosections for an average composition in the NCKFMASH system. Calculated pseudosection is in accordance with field and petrographic observation, except that symplectite minerals does not appear in the model, suggesting that formation of symplectite was affected by effective bulk compositions (EBC), rather than whole-rock composition. So EBC model was calculated using modal abundance and average composition of symplectite minerals. In pseudosection calculated for EBC, spinel + gedrite + cordierite is stable over wide range of P and T. Peak metamorphic condition for symplectites are estimated as 750°C at 4.1 kbar. Staurolite-bearing symplectites appeared during retrograde isobaric path at 600°C and 4.1 kbar. Based on calculated pseudosections and estimated P and T, an isobaric retrograde anticlockwise P-T path is proposed for the Sarabi migmatites. Metamorphism and migmatization in the area is linked to the major plutonism phases of the Sanandaj–Sirjan Zone in Middle-Jurassic under high T-low P conditions, during the evolution of Neo-Tethys. [ABSTRACT FROM AUTHOR]

Abstract We found in our research that andalusite aggregate fired in a reducing atmosphere exhibits a lower mullitization rate than that fired in an air atmosphere. For investigating the effect of atmosphere on the transformation of andalusite and the properties of andalusite-containing refractories, andalusite powder (≤0.074 mm) and refractories containing andalusite aggregate (3–1 mm) were fired in air and carbon embedding, respectively. The phases and microstructure of the andalusite fired in both atmospheres were characterized by X-ray diffraction and scanning electron microscopy, respectively. The correlations of the properties of the andalusite-bearing refractories with the firing atmospheres were investigated in terms of volume stability, mechanical strength, and thermal shock resistance. The difference in the properties of the refractories was discussed with respect to the varied transformation rates of andalusite, and in terms of the different viscosities of the silica-rich glass caused by the different atmospheres. [ABSTRACT FROM AUTHOR]

The variety of sizes and morphology of grains and chemical composition of native Au, and the diversity of mineral productive associations in the new ore occurrences of the Western and Central Taimyr (the Minina–Bolshevik miogeocline and the Shrenk–Faddeevskaya accretionary mineragenic zones) indicate the complex multicomponent composition of ore-forming systems and different physicochemical conditions of the formation of gold ore mineralization. The native Au characteristics and specific features of the geological structure of the objects point to the significant gold ore potential of the Central Sector of the Russian Arctic. [ABSTRACT FROM AUTHOR]

Abstract Bauxite-SiC refractories as the working lining of cement rotary kiln are subjected to severe alkali attack due to alternative fuel combustion. Herein, the present work aims to enhance their alkali attack resistance via incorporation of different types of andalusite (aggregates and powder). Results show that addition of andalusite reduces penetration of alkali vapor by decreasing their pore size. In particular, the presence of andalusite aggregate traps alkali vapor inside its pore network, retarding the corrosion of refractory matrix. By comparison, the presence of andalusite powder contributes to formation of liquid corrosion products to block the pores, which prevent alkali vapor from further penetration. Incorporation of andalusite into BSRs is straightforward and sought-after, providing an effective approach for high-performance refractory materials with excellent alkali attack resistance. [ABSTRACT FROM AUTHOR]

We document a dichromatism effect in gem andalusite that shifts from light brownish pink at low thickness to medium green at high thickness. This is roughly reverse to that usually observed in other dichromatic materials. We show that this is due to a very strong pleochroism in andalusite, when dichromatism in other materials is due to an alexandrite effect. Here, colors varies from a strongly absorbing orangey-brown in the c direction to much less absorbing medium green in a and b directions. The brown absorption is so strong that it becomes opaque (total absorption) for thickness above about 1.5 mm (this value may vary according to concentration of the chromophore and intensity of the light source), and hence does not contribute to coloration anymore. For such high thicknesses, only the a and b directions remain transparent and hence only the green component contributes to the color: the sample appears green. For lower thicknesses, the green color combines with the orangey-brown color that becomes transparent along the c direction, resulting in a light brownish pink. From trace elements analysis in zoned samples, we also confirm that the dark orangey-brown color is due to Fe 2+ -Ti 4+ , and bring evidences that the light green color is mostly due to Fe, either in the form of isolated Fe 3+ or Fe 2+ -Fe 3+ IVCT, with possibly some contributions from isolated Mn 3+ . [ABSTRACT FROM AUTHOR]

Petrographic comparison of andalusite in the contact aureole of the Fangshan pluton, Zhoukoudian, Beijing, China, and hornfels in the aureole of the Markfield diorite, Leicestershire, England, shows that spots characteristic of the outer zones of contact metamorphic aureoles did not form during the progressive stage of contact metamorphism, but are pseudomorphs after earlier andalusite with characteristic chiastolite microstructure. The baked margin produced by contact metamorphism of syenite against a dyke in the Houshihushan ring complex, Shanhaiguan, Hebei Province, China, is an unusual feature caused by the dyke’s role as a feeder to a family of cone-sheets. [ABSTRACT FROM AUTHOR]

Introduction The area studied is located north of Azna (Lorestan Province) in a small portion of the Sanandaj – Sirjan structural zone (Mohajjel et al., 2003).This area is part of the Zagros orogenic belt, formed by the opening and closure of Neotethyan ocean. From NE to SW, it consists of three parallel tectonic regions: the Orumieh-Dokhtar magmatic belt, the Sanandaj-Sirjan structural zone and the Zagros thrust-fold belt (Ghasemi and Talbot, 2005). The Sanandaj-Sirjan structural zone is a metamorphic belt composed mostly of greenschist, amphibolite and eclogite facies rocks. The development of the zonetook placeduring the opening of the Tethys ocean and its subsequent closing during the Cretaceous and earlyTertiary convergence of the Afro-Arabian and Eurasian plates (Mohajjel and Fergusson, 2000). The second stage of metamorphism and deformation of the zone, designated D2, is the most important, resulting from the opening and closure of the Neotethyan ocean and the collision of the Arabian plate with the southwestern part of central Iran in the Late Cretaceous to Tertiary (Laramideorogenic phase) (Ghasemi and Talbot, 2005; Aghanabati, 2004; Mohajjel et al., 2003; Mohajjel and Fergusson, 2000; Alavi, 1994). In the Sanandaj-Sirjanzone, which includes the Azna area, Cretaceous granitic intrusions into the schists were followed byfolding and faulting. The intrusions produced contact metamorphism, and have lens-shaped outlines, trendingNW-SE. Consequently, the Azna area has a varied petrologic assemblage with polyphase metamorphism and deformation, including schists, metabasites and mylonitic granites. The phases include: 1. Deformation D1, and dynamothermal metamorphism (M1),a result of the subduction of Neotethysoceanic crust beneath the Iranian plate in the Late Jurassic. 2.Deformation D2, and thermal metamorphism (M2),a result of Paleocene continental collision and 3. Deformation D3, and dynamic metamorphism (M3). This deformation is a progressive deformation that hasproduced the current morphologyof the Sanandaj-Sirjan zone (Shabanian Borujeni, 2008). In this paper we focused on petrography and mineral chemistry and thermodynamic conditions of the metapelites. Materials and methods The chemical compositions of minerals were determined by a CAMECA SX100 electron microprobe (EMP) at Universität Stuttgart (Germany). The instrument is equipped with five wavelength dispersive spectrometers. The beam current and acceleration voltage were 15 nA and 15 kV, respectively. v Discussion and Results The Azna regional metamorphic rocks include quartz-feldspar schists, mica schists, andalusite-bearing schists and quartzites. The Azna metapelites are schists, containing quartz, feldspars, andalusite, muscovite, biotite, muscovite, chlorite and garnet, in variable proportions, characterized byporphyroblastic and lepidoblastic textures. Based on mineralogy, minerals of these rocks contain andalusite, garnet, feldspar, muscovite, biotite, quartz and chlorite. Microprobe analyses show that the mineral compositions are as follows: White micas in the andalusite-bearing schists are muscovite, plagioclases are albite-oligoclase, garnets are almandine-spessartine with weak chemical zoning and biotites are siderophylite-annite. Based on geothermobarometry, these rocks formed in the hornblende-hornfels facies and the low pressure part of the amphibolite facies,with temperatures about 562-692 °C and pressures1.07-4.12 kbar. After the regional metamorphism of these rocks,granitoidintrusions causedthermal metamorphism of these rocks and the formation of andalusite-bearing schists. Acknowledgments The authors wish to thank the Office of Graduate Studies of the University of Isfahan for their support. We also thank Prof. Hans-JoachimMassonne, who played major roles during the microprobe analysis of minerals at the InstitutfürMineralogie und Kristallchemie, Universität Stuttgart (Germany). References Aghanabati, A., 2004. Geology of Iran. Geological Survay of Iran, Tehran, Iran, 586 pp (in Persian). Alavi, M., 1994. Tectonics of the Zagros Orogenic Belt of Iran: New Data and Interpretations. Tectonophysics, 22(1): 211–238. Ghasemi, A. and Talbot, C.J., 2005. A new tectonic scenario for the Sanandaj-Sirjan Zone (Iran). Journal of Asian Earth Scines, 5(1):1-11. Mohajjel, M. and Fergusson, C.L., 2000. Dextral transpression in Late Cretaceous contatinetal collision, Sanandaj-Sirjan Zone (Western Iran). Journal of Structural Geology, 22(1): 1125-1139. Mohajjel, M., Fergusson, C.L. and Sahandi, M.R., 2003. Cretaceous-Tertiary contatinetal collision, Sanandaj- Sirjan Zone, Western Iran. Journal of Asian Earth Sciences, 21(1): 397-412. Shabanian borujeni, N., 2008. Petrology and tectonic setting of the Azna granitoid masses (Sanandaj-Sirjan Zone, Iran). Ph.D. Thesis, University of Isfahan, Iran, 192 pp.

Mullite and alumina are common in high-temperature applications because of their low thermal expansion coefficient and good thermal shock resistance. Evolution of SiC in the matrix and using it as reinforcing phase can improve thermo-mechanical properties of these materials. Also, in-situ formation of the reinforcing phases by using inorganic materials is an economical process. In this work, crystallization of SiC as reinforcing phase in the matrix of mullite-alumina by carbothermal reaction processes of inorganic materials (andalusite and kaolinite) was studied. According to the ratio of C/SiO2 and process conditions, some properties of the composite such as phase transformation, microstructure and physical and mechanical properties were investigated. The results showed that optimal ratio of C/SiO2 and firing temperature of densification to form SiC crystals were 3.5 and 1600°C for andalusite and 5.5 and 1500°C for kaolinite.

The distribution and textural features of staurolite--Al2SiO5 mineral assemblages do not agree with predictions of current equilibrium phase diagrams. In contrast to abundant examples of Barrovian staurolite--kyanite--sillimanite sequences and Buchan-type staurolite--andalusite--sillimanite sequences, there are few examples of staurolite--sillimanite sequences with neither kyanite nor andalusite anywhere in the sequence, despite the wide (~2.5 kbar) pressure interval in which they are predicted. Textural features of staurolite--kyanite or staurolite-- andalusite mineral assemblages commonly imply no reaction relationship between the two minerals, at odds with the predicted first development (in a prograde sense) of kyanite or andalusite at the expense of staurolite in current phase diagrams. In a number of prograde sequences, the incoming of staurolite and either kyanite, in Barrovian sequences, or andalusite, in Buchan-type sequences, is coincident or nearly so, rather than kyanite or andalusite developing upgrade of a significant staurolite zone as predicted. The width of zones of coexisting staurolite and either kyanite, in Barrovian sequences, or andalusite, in Buchan-type sequences, is much wider than predicted in equilibrium phase diagrams, and staurolite commonly persists upgrade until its demise in the sillimanite zone. We argue that disequilibrium processes provide the best explanation for these mismatches. We suggest that kyanite (or andalusite) may develop independently and approximately contemporaneously with staurolite by metastable chlorite-consuming reactions that occur at lower P--T conditions than the thermodynamically predicted staurolite-to-kyanite/andalusite reaction, a process that involves only modest overstepping (<15°C) of the stable chloriteto- staurolite reaction and which is favoured, in the case of kyanite, by advantageous nucleation kinetics. If so, the pressure difference between Barrovian kyanite-bearing sequences and Buchan andalusite-bearing sequences could be ***1 kbar or less, in better agreement with the natural record. The unusual width of coexistence of staurolite and Al2SiO5 minerals, in particular kyanite and andalusite, can be accounted for by a combination of lack of thermodynamic driving force for conversion of staurolite to kyanite or andalusite, sluggish dissolution of staurolite, and possibly the absence of a fluid phase to catalyse reaction. This study represents an example of how kinetic controls on metamorphic mineral assemblage development have to be considered in regional as well as contact metamorphism. [ABSTRACT FROM AUTHOR]