Xenocrysts and megacrysts of alkali olivine-basalt-basanite-nephelinite association makhtesh ramon (israel): interaction with transporting magmas and morphological adjustment

Xenocrysts and megacrysts hosted in the rocks of Early Cretaceous olivine-basalt-basanite-nephelinite association that outcropped in erosion crater of Makhtesh Ramon (Natural Reserve of Mishmar ha-Nagev, Israel) are the topic of the current research. Magmatic rock association contains the wide spectrum of xenoliths trapped at different crustal levels. These are upper mantle, lower, and upper crustal xenoliths. Mantle xenoliths are represented by peridotites, olivine clinopyroxenites, clinopyroxenites, olivine websterites, websterites and their amphibole-bearing analogs. Lower crustal xenoliths are mafic granulites, such as metagabbros and plagioclasites, upper crustal xenoliths are the fragments of Neoproterozoic tuffs. Xenocrysts and megacrysts are fragments of xenoliths that chipped from them during their transportation to the surface. Different rate of xenoliths, xenocrysts, and megacrysts alteration by host magma and late fluids is a common petrographic particularity. The fluid alteration occurred at phreatomagmatic stage of magma crystallization. Alteration is observed by the appearance of new textures and products of reactional interaction. Xenocrysts and megacrysts are mainly represented by minerals that compatible with rock magmatic association. These are olivine, clinopyroxene, amphibole, nepheline, plagioclase, anorthoclase, apatite, magnetite, and spinel. Xenocrysts of quartz and orthopyroxene are incompatible to host rock magmatic association under-saturated in SiO2. Main reasons determining interaction between magma and xenolith are rapid decompression, metamorphism and metasomatism. Xenocrysts are subjected to metamorphism that corresponds to high-temperature facies of contact metamorphism, up to the partial melting of xenocrysts. Metasomatism is smoothing out the composition of xenocrysts to the composition of the same minerals that crystallized from host melt. There are several important criterions, which permit to identify xenocrysts and divide them from phenocrysts. These are partial melting, solid-state decomposition, recrystallization of primary (before-trapping) textures, recrystallization and self-faceting of initially anhedral grains into the crystals with perfect habit. Chemical composition of xenocrysts has both mineral - geochemical indications of xenogenic origin and new-formed sings of alteration

Walstromite, BaCa2(Si3O9), from Rankinite Paralava within Gehlenite Hornfels of the Hatrurim Basin, Negev Desert, Israel

Walstromite, BaCa2Si3O9, known only from metamorphic rocks of North America, was found in small veins of unusual rankinite paralava within gehlenite hornfelses of the Hatrurim Complex, Israel. It was detected at two localities—Gurim Anticline and Zuk Tamrur, Hatrurim Basin, Negev Desert. The structure of Israeli walstromite [with P1 space group and cell parameters a = 6.74874(10)Å, b = 9.62922(11) Å, c = 6.69994(12) Å, α = 69.6585(13)°, β = 102.3446(14)°, γ = 96.8782(11)°, Z = 2, V = 398.314(11) Å3) is analogous to the structure of walstromite from type locality—Rush Creek, eastern Fresno County, California, USA. The Raman spectra of all tree minerals exhibit bands related to stretching symmetric vibrations of Si-O-Si at 650–660 cm−1 and Si-O at 960–990 cm−1 in three-membered rings (Si3O9)6−. This new genetic pyrometamorphic type of walstromite forms out of the differentiated melt portions enriched in Ba, V, S, P, U, K, Na, Ti and F, a residuum after crystallization of rock-forming minerals of the paralava (rankinite, gehlenite-åkermanite-alumoåkermanite, schorlomite-andradite series and wollastonite). Walstromite associates with other Ba-minerals, also products of the residual melt crystallization as zadovite, BaCa6[(SiO4)(PO4)](PO4)2F and gurimite, Ba3(VO4)2. The genesis of unusual barium mineralization in rankinite paralava is discussed. Walstromite is isostructural with minerals—margarosanite, BaCa2Si3O9 and breyite, CaCa2(Si3O9), discovered in 2018

Not Only Garnets…

Garnets have been known to man since time immemorial and are used in a wide variety of applications as well as being prototypes of useful synthetic materials. Our investigations show that in nature, garnets and minerals with a langasite-type structure can be very close in composition. Examples are cubic Ti-rich garnets with the common formula Ca3(Ti4+,Fe3+,Al)2(Si,Fe3+,Al)3O12 and the new trigonal mineral qeltite, Ca3Ti(Fe3+2Si)Si2O14, which occur in paralavas of the pyrometamorphic Hatrurim Complex, Israel. Synthetic compounds of the langasite family are important because of their functional properties, such as unique piezoelectricity, high thermal stability, and low acoustic losses, as well as optical nonlinearity and multiferroicity. Qeltite is the first high-temperature terrestrial mineral with a langasite-type structure, the description of which was a catalyst for the discovery in pyrometamorphic rocks of the Hatrurim Complex of a whole series of new natural phases with langasite-type structure and varied composition (A3BC3D2O14, where A = Ca and Ba; B = Ti, Nb, Sb, and Zr; C = Ti, Al, Fe, and Si; and D = Si). We think that qeltite and other minerals with langasite-type structure may be relatively widely distributed in terrestrial rocks that form under similar conditions to those of Ti-rich garnet but are missed by researchers

Molecular Hydrogen in Natural Mayenite

In the last 15 years, zeolite-like mayenite, Ca12Al14O33, has attracted significant attention in material science for its variety of potential applications and for its simple composition. Hydrogen plays a key role in processes of electride material synthesis from pristine mayenite: {Ca12Al14O32}2+(O2)!{Ca12Al14O32}2+(e)2. Apresence of molecular hydrogen in synthetic mayenite was not confirmed by the direct methods. Spectroscopy investigations of mayenite group mineral fluorkyuygenite, with empirical formula (Ca12.09Na0.03)P 12.12(Al13.67Si0.12Fe3+ 0.07Ti4+ 0.01)P 12.87O31.96 [F2.02Cl0.02(H2O)3.22(H2S)0.15 0.59]P 6.00, show the presence of an unusual band at 4038 cm1, registered for the first time and related to molecular hydrogen, apart from usual bands responding to vibrations of mayenite framework. The band at 4038 cm1 corresponding to stretching vibrations of H2 is at lower frequencies in comparison with positions of analogous bands of gaseous H2 (4156 cm1) and H2 adsorbed at active cation sites of zeolites (4050–4100 cm1). This points out relatively strong linking of molecular hydrogen with the fluorkyuygenite framework. An appearance ofH2 in the fluorkyuyginite with ideal formula Ca12Al14O32[(H2O)4F2], which formed after fluormayenite, Ca12Al14O32[ 4F2], is connected with its genesis. Fluorkyuygenite was detected in gehlenite fragments within brecciaed pyrometamorphic rock (Hatrurim Basin, Negev Desert, Israel), which contains reduced mineral assemblage of the Fe-P-C system (native iron, schreibersite, barringerite, murashkoite, and cohenite). The origin of phosphide-bearing associations is connected with the e ect of highly reduced gases on earlier formed pyrometamorphic rocks

New Mineral with Modular Structure Derived from Hatrurite from the Pyrometamorphic Rocks of the Hatrurim Complex: Ariegilatite, BaCa12(SiO4)4(PO4)2F2O, from Negev Desert, Israel

Ariegilatite, BaCa12(SiO4)4(PO4)2F2O (R3m, a = 7.1551(6) Å, c = 41.303(3) Å, V = 1831.2(3) Å3, Z = 3), is a new member of the nabimusaite group exhibiting a modular intercalated antiperovskite structure derived from hatrurite. It was found in a few outcrops of pyrometamorphic rocks of the Hatrurim Complex located in the territories of Israel, Palestine and Jordan. The holotype specimen is an altered spurrite marble from the Negev Desert near Arad city, Israel. Ariegilatite is associated with spurrite, calcite, brownmillerite, shulamitite, CO3-bearing fluorapatite, fluormayenite-fluorkyuygenite and a potentially new mineral, Ba2Ca18(SiO4)6(PO4)3(CO3)F3O. Ariegilatite is overgrown and partially replaced by stracherite, BaCa6(SiO4)2[(PO4)(CO3)]F. The mineral forms flat disc-shaped crystals up to 0.5 mm in size. It is colorless, transparent, with white steaks and vitreous luster. Optically, ariegilatite is uniaxial, negative: ! = 1.650(2), " = 1.647(2) ( = 589 nm). The mean composition of the holotype ariegilatite, (Ba0.98K0.01Na0.01)S1(Ca11.77Na0.08Fe2+ 0.06Mn2+ 0.05Mg0.04)S12(Si3.95Al0.03Ti0.02)S4(P1.70C0.16Si0.10S6+ 0.03 V0.01)S2F2.04O0.96, is close to the end-member formula. The structure of ariegilatite is described as a stacking of the two modules {F2OCa12(SiO4)4}4+ and {Ba(PO4)2}4 along (001). Ariegilatite, as well as associated stracherite, are high-temperature alteration products of minerals of an early clinker-like association. These alterations took place under the influence of pyrometamorphism by-products, such as gases and fluids generated by closely-spaced combustion foci

Uvarovite from Reduced Native Fe-Bearing Paralava, Hatrurim Complex, Israel

A new genetic type of chromium garnet—uvarovite with the simplified formula Ca3(Cr,Al,Ti4+,V3+)2(Si,Al)3O12—was detected in unusual wollastonite-gehlenite-bearing paralava within the Hatrurim Complex in Israel. The pyrometamorphic rocks of that Complex usually formed in the sanidinite facies (low pressure and high temperature) and, as a rule, under oxidized conditions. This paralava contains nodules and grain aggregates of native Fe, usually distributed linearly in the rock or located close to gaseous voids. The presence of native iron droplets in association with the “meteoric” phosphide—schreibersite, suggests that the formation of paralava occurred under high-reducing conditions and high temperature, reaching 1500°C. Uvarovite forms xenomorphic grains either randomly distributed within the rock or flattened crystals on the walls of gaseous voids. Analyzed uvarovite indicates a significant enrichment in Ti4+ (up to 8 wt.% TiO2) and V3+ (up to 4.5 wt.% V2O3), the highest concentrations documented for uvarovite. Unlike known uvarovite from different localities, uvarovite from this study does not contain Fe3+, and Fe2+ is present in insignificant amounts. The obtained structural data reveal that the high contribution of hutcheonite, Ca3Ti4+2SiAl2O12 (up to 18%), and goldmanite, Ca3V3+2Si3O12 (up to 11%), end-members increases the lattice parameter a to >12.00 Å. The crystallization of uvarovite occurs in the narrow interval of oxygen fugacity, a little above the iron-wüstite buffer ƒO2 ≥ ΔIW. Uvarovite xenomorphic grains formed due to the decomposition of wollastonite and chromite, including H2S from the intergranular melt/fluid according to the following reaction: Ca3Si3O9 + Fe2+Cr3+2O4 + H2S → Ca3Cr2Si3O12 + FeS + H2O, while the flattened crystals grew from specific melt that formed on the walls of the voids as a result of exposure of hot gas flow. The comparison of the obtained results with available chemical data from previous studies reveals a gap in the natural isomorphic series between andradite and uvarovite

Kahlenbergite KAl11O17, a new β-alumina mineral and Fe-rich hibonite from the Hatrurim Basin, the Negev desert, Israel

Kahlenbergite, ideally KAl11O17, and Fe-rich hibonite, CaAl10Fe2O19, are high-temperature minerals found in “olive” subunits of pyrometamorphic rocks, in the Hatrurim Basin, the Negev desert, Israel. The crystal structures of both minerals are refined using synchrotron radiation single-crystal diffraction data. The structure of kahlenbergite (P63/mmc; a = 5.6486(1) A; b = 22.8970(3) A; Z = 2) exhibits triple spinel blocks and so-called R blocks. The spinel blocks show mixed layers with AlO6 octahedra and (Al0.56Fe0.44)O4 tetrahedra and kagome layers with (Al0.92Fe0.08)O6 octahedra. One-dimensional diffuse scattering observed parallel to c* implies stacking faults in the structure. Also, in one of the investigated kahlenbergite crystals additional reflections can be identified, which obviously belong to a second phase with a smaller lattice parameter c: Fe3+-rich hibonite. The structure of hibonite contains the same spinel blocks as kahlenbergite. The R blocks in hibonite contain Ca atoms, AlO5 bipyramids, and AlO6 octahedra, whereas the R blocks in kahlenbergite contain potassium atoms and AlO4 tetrahedra

Mineralogical, Geochemical, and Rock Mechanic Characteristics of Zeolite- Bearing Rocks of the Hatrurim Basin, Israel

The Hatrurim Basin, Israel, is located on the western border of the Dead Sea Transform. This is one of the localities of a unique pyrometamorphic complex whose genesis remains problematic. This paper deals with zeolite-bearing rock that is known in the Hatrurim Basin only. The strata subjected to zeolitization is called the “olive unit” and consists of anorthite–pyroxene (diopside–esseneite) hornfels. Zeolitization occurred in an alkaline environment provided by the interaction of meteoric water with Portland-cement-like rocks of the Hatrurim Complex. The resulting zeolite-bearing rocks contain 20–30% zeolitic material. The main zeolitic minerals are calcic: thomsonite-Ca Sr, phillipsite-Ca, gismondine-Ca, and clinoptilolite-Ca. The remainder is calcite, diopsidic pyroxene, garnets (either Ti-andradite and/or hydrogrossular), and less frequently, fluorapatite, opal, and others. Their major mineralogical and chemical compositions resemble carbonated zeolite-blended Portland mortar. Rocks show different values of porosity. Their mechanical characteristics are much better for samples with porosity values below 24%. The related parameters are like those of blended concretes. The minimal age of zeolitization is 5 Ka. The natural zeolite-bearing rocks are resistant to weathering in the Levant desert climate

First <i>In Situ</i> Terrestrial Osbornite (TiN) in the Pyrometamorphic Hatrurim Complex, Israel

AbstractOsbornite (TiN) is extremely rare in nature (commonly found in enstatite meteorites) and has not yet been identified correctly to form naturally in terrestrial settings. Due to its thermodynamic stability and thermal shock resistance, TiN has wide industrial applications, mainly as coatings. However, as the melting temperature of TiN is very high (~3000°С), coatings are produced at much lower temperatures via physical or chemical vapor deposition. Also, anthropogenic analogues of osbornite are often observed in pyrometallurgical slags. Therefore, it is critical to distinguish between anthropogenic and naturally occurring osbornite. A detailed petrographic study was undertaken on in situ osbornite found within unusual gehlenite-bearing breccias from wadi Zohar, Negev Desert of the pyrometamorphic Hatrurim Complex. The Hatrurim Complex, which extends through Israel, Palestine, and Jordan within the Dead Sea Rift zone, mainly comprises larnite, gehlenite, and spurrite rocks. Osbornite, in close association with iron phosphides, barringerite, and schreibersite, occurs at contacts between gehlenite, paralava, and calcinated clasts of host sedimentary rocks. Based on investigation of pseudowollastonite and Fe-P series phases, osbornite is formed at low pressure, extremely high temperatures (~1200-1500°С), and reduced conditions, following pyrolysis of organic matter contained in the sedimentary protolith. This is the first identification of in situ osbornite in terrestrial rocks and indicates that high-temperature and highly reduced conditions, which are common for meteorites, may occur at/near the Earth’s surface as a result of sustained pyrometamorphism in particular settings. Our findings also provide relevant data and criteria for comparing osbornite occurrences elsewhere and ultimately evaluating their origins

Mud volcano origin of the Mottled Zone, South Levant

The Mottled Zone (MZ) or Hatrurim Formation, which occurs near the Levantine Transform in the South Levant, has been studied during the last 150 years but its origin remains debatable. Mottled Zone Complex/Complexes (MZC/MZCs) consist of brecciated carbonate and low-temperature calcium-hydrosilicate rocks, which include unusual high- and ultra-high-temperature low-pressure (HT-LP) metamorphic mineral assemblages. The MZ has been regarded as a product of combustion of bituminous chalks of the Ghareb Fm. of Cretaceous (Maastrichtian) age. In this paper we present detailed geographic, geomorphologic, structural and geological data from the MZCs of the South Levant, which show that the MZCs cannot be stratigraphically correlated with the Ghareb Fm., because MZC late Oligocene–late Pleistocene deposits occur within or unconformably, i.e., with stratigraphic hiatus, overlap both the late Cretaceous and, in places, Neogene stratigraphic units. We propose an alternative model for the formation of MZCs by tectonically induced mud volcanism during late Oligocene–late Pleistocene time. This model explains (i) the presence of dikes and tube-like bodies, which consist of brecciated exotic clastic material derived from stratigraphically and hypsometrically lower horizons; (ii) mineral assemblages of sanidinite facies metamorphism; (iii) multi-stage character of HT-LP pyrometamorphism; and (iv) multi-stage low-temperature hydrothermal alteration. High temperatures (up to 1500 °C) mineral assemblages resulted from combustion of hydrocarbon gases of mud volcanoes. Mud volcanism was spatially and structurally related to neotectonic folds and deformation zones formed in response to opening of the Red Sea rift and propagation of the Levantine Transform Fault. Our model may significantly change the prospects for oil-and-gas deposits in the region