Ye. Vapnik

Gas Fire from Mud Volcanoes as a Trigger for the Appearance of High-Temperature Pyrometamorphic Rocks of the Hatrurim Formation (Dead Sea Area)

Rock complexes of the Hatrurim Formation are largely confined to axial parts of gentle anticlinal uplifts. The rocks are partly localized in the complicating synclines on near-horizontal Campanian strata (Mishash Formation). The platform cover of this area is crosscut by a young rift valley and is divided by faults into blocks. The Hatrurim basin hosted in one of the blocks associates with the synclinal structure (8 × 5 km), the eastern limb of which is bordered by listric walls of the Dead Sea Rift valley (Fig. 3). The block is surrounded by anticlines with small gas (Zoar, Kidod, and Haqanaim) and oil (Zuk-Tamrur and Gurim) traps. The rift valley is characterized by salt diapirism (Sdom Dome). Asphaltene, bitumen, and oil occurrences are observed in coastal areas of the Dead Sea [8]. Numerous natural cataclysms related to bitumen burning and gas explosions are mentioned in biblical history. The landscapes of the Hatrurim, Ma’ale Adummim, Jabel Harmun, and Hyrcania complexes are distinguished in the surrounding cuesta topography characteristic of sedimentary sequences of the Judea Mountains and the Negev Desert. The relief of the Hatrurim basin is marked by several hundred newly formed cones largely composed of mud breccia. In some places, the breccias are characterized by vague bedding discordant with that of host sedimentary rocks. In the southern part of the basin, small individual cones and their chains are located on the eroded surface of the phosphorite and cherty Mishash Formation. In the north, large cones crown the mud breccia. The Ma’ale Adummim and Hyrcania complexes are characterized by a specific relief (truncated cones a few kilometers across at the base and an order of magnitude lower in height). The MZ complexes (particularly, Maqarin) in Jordan are feebly marked. Breccias are distributed through the entire section of the Hatrurim basin (Fig. 4). Rock fragments are composed of chalk, marl, and dolomite with subordinate cherts and phosphorites of the Mishash Formation.

Compositions and formation conditions of fluid inclusions in emerald from the Maria deposit (Mozambique)

Abstract The compositions of fluid inclusions hosted in emerald and quartz (the Maria deposit, Mozambique) were studied using microthermometric and Raman microprobe techniques. The fluid inclusions in the emerald contain fluids within the Na-Ca-Mg-(HCO3)--(CO3)2--Cl-H2O system saturated in carbonic acid brines. Nahcolite is a main daughter solid phase within the fluid inclusions. The mean nahcolite and NaCl contents are 25 and 5 wt.%, respectively. Mg-calcite, magnesite, calcite and aragonite are also identified as daughter phases in the fluid inclusions. Many fluid inclusions show necked-down appearance. Groups of nahcolite crystals often make up ~50 vol.% of necked-down inclusions. It seems that zones of fluid inclusions with numerous birefringent solid phases are distinctive of the Maria emerald deposit. The likely conditions of emerald growth are 400 < T < 500°C and 3 < P < 4 kbar.

Flamite, (Ca,Na,K)2(Si,P)O4, a new mineral from ultrahigh-temperature combustion metamorphic rocks, Hatrurim Basin, Negev Desert, Israel

Abstract Flamite (Ca,Na,K)2(Si,P)O4 (P63; a = 43.3726(18), c = 6.8270(4) Å ; V = 11122.2(9) Å3), a natural analogue of the P,Na,K-doped high-temperature α-Ca2SiO4 modification, is a new mineral from Ca-and Al-rich paralava, an ultrahigh-temperature combustion metamorphic melt rock. The type locality is situated in the southern Hatrurim Basin, the Negev Desert, Israel. Flamite occurs as regular lamellar intergrowths with partially hydrated larnite, together with rock-forming gehlenite, rankinite and Ti-rich andradite, minor ferrian perovskite, magnesioferrite, hematite, and retrograde ettringite and calcium silicate hydrates. The mineral is greyish to yellowish, transparent with a vitreous lustre, non-fluorescent under ultraviolet light and shows no parting or cleavage; Mohs hardness is 5-5½; calculated density is 3.264 g cm-3. The empirical formula of holotype flamite (mean of 21 analyses) is (Ca1.82Na0.09K0.06(Mg,Fe,Sr,Ba)0.02)∑1.99(Si0.82P0.18)∑1.00O4. The strongest lines in the powder X-ray diffraction pattern are [d, Å (Iobs)]: 2.713(100), 2.765(44), 2.759(42), 1.762(32), 2.518(29), 2.402(23), 2.897(19), 1.967(18), 2.220(15), 1.813(15). The strongest bands in the Raman spectrum are 170, 260, 520, 538, 850, 863, 885, 952 and 1003 cm-1.

The Katherina Ring Complex (Sinai Peninsula, Egypt): Sequence of emplacement and petrogenesis

The Katherina Ring Complex (KRC) in the central Sinai Peninsula, Egypt, was formed in three consecutive stages: volcanic, subvolcanic, and plutonic. The outer Katherina ring dike, about 30 km in diameter, marks the contour of a paleocaldera. Volcanic ignimbrite extrusions representing the earliest stage of the KRC were followed by emplacement of subvolcanic peralkaline microgranite bodies. The ring dikes are composed mainly of porphyritic quartz monzonite and plagioclase-rich quartz syenite, with less abundant alkali feldspar quartz syenite and peralkaline granite. The central alkaline granite pluton (ca. 210 km2) was emplaced at ∼595 Ma. The quartz monzonite–syenite group is characterized by positive Eu anomalies (Eu/Eu* = 1.1-1.6), which is consistent with its enrichment in accumulated plagioclase crystals (xenocrysts). These features, along with the positive εNd(T) values in quartz monzonite (up to +5.6) suggest that the initial silicic magma was hybridized by plagiclase-rich mafic magma. Mineral geothermometry and melt inclusion studies point to the formation of the silicic magmas at high temperatures, up to 900 to 1000 °C. Oxygen and Sr-Nd isotope data suggest that the source of the magmas was moderately depleted mantle or young juvenile crust. The trend of compositional change from quartz alkali feldspar syenite to alkali feldspar and peralkaline granite is consistent with a fractional crystallization model. A specific feature of the magma differentiation process is that the residual melt separation could occur when the magma was ∼55 percent crystallized (“rigid percolation threshold”) and clusters of crystals formed a rigid skeleton in the magma. At this stage, residual melt flowed pervasively through the pore space. The suggested model of melt separation alleviates the problem of a differentiation process since it does not require crystal settling that seems unrealistic in highly viscous silicic magmas at shallow depth. Chemical and Nd isotopic distinctions between the leucocratic volcanic–subvolcanic rocks (εNd(T) = 4.2-4.6) and the Katherina pluton granite (2.6-3.9) suggest that the silicic magmas of the volcanic-subvolcanic and the plutonic stages were probably produced from different mantle-derived sources.

Formation of emeralds at pegmatite-ultramafic contacts based on fluid inclusions in Kianjavato emerald, Mananjary deposits, Madagascar

Abstract Kianjavato emerald (Mananjary deposits, East coast of Madagascar) was formed during metasomatic processes at the contact between pegmatites and hornblendites. The metasomatic exchange was related to a Pan-African tectonometamorphic event. Fluid inclusions in the Kianjavato emerald and quartz were studied by means of microthermometry and Raman probe analysis. Three main types of inclusions were revealed: CO2-rich, CH4-rich and aqueous-rich, with a salinity of ~2 wt.% NaCl equiv. The inclusions occurred along the same primary and pseudosecondary trails and were considered to be formed simultaneously. Based on fluid-inclusion data, the conditions of emerald growth were 250°C < T < 450°C and P = 1.5 kbar. The fluid inclusion data for Kianjavato emerald were compared to the data for another Madagascar emerald, Ianapera. The latter is of similar age, but its genesis was determined by a shearing event. Our fluid inclusion data suggested that shearing was also important as a mechanism of introducing CO2-rich fluid for the genesis of the Kianjavato emerald.

Fluid Inclusions in Ianapera Emerald, Southern Madagasca

The Ianapera emerald deposit (South Madagascar) formed by metasomatism along the contact of migmatitic gneiss and lenses of serpentinite and amphibolite, initiated by shearing related to a Pan-African tectono-metamorphic event. We report the results of fluid inclusion studies on Ianapera emerald employing microthermometry, Raman spectrometry, and electron microprobe and SEM analysis. Several types of inclusions are present within the same primary inclusion population: (1) aqueous-rich inclusions containing daughter carbonate phases and NaCl-HCO3 - solution, commonly with a salinity of ∼7 wt% NaCl equiv.; (2) CO2 ± CH4 inclusions mostly of high density (about 1 g/cm3) which usually contain several daughter carbonate phases; (3) multi-aggregate solid inclusions composed of hydrocarbon-sulfur-carbonate aggregates; and (4) oil-inclusions. The conditions of emerald growth determined on the basis of fluid inclusion characteristics and a petrogenetic grid are T = 630-710°C and P = 5.0-5.8 kbars. The Ianapera emerald is unique with regard to its chemical composition, fluid inclusion content, and high P-T conditions of growth.

Melt inclusions in granitoids of the Timma igneous complex, southern Israel

Abstract High temperature microthermometry and Scanning Electron Microprobe (SEM) analyses were used to study natural magmatic remnants in quartz crystals in granitoids from the Timna Igneous Complex, southern Israel, and to constrain physicochemical parameters during their crystallization. For the porphyritic granite, alkali granite and quartz monzodiorite, liquidus temperatures are 710-770, 770-830 and 770-840°C, respectively; solidus temperatures are 690-770, 710-790 and 770°C, respectively. Pressures during crystallization and water content in the magmas were determined using the phase diagram of the modal granite system. The determined P-T-conditions are typical for water-saturated granitoid magmas (>4-8 wt.%) generated and crystallized at a shallow crustal level. SEM data on melt inclusions support conclusions of previous investigations on two types of granitoid magmas exposed in the Timna Igneous Complex: the porphyritic and alkali granites. Different trends of crystallization are proposed for these granites. Crystallization of the porphyritic granite started with cotectic crystallization of plagioclase and terminated in residual K-feldspar-rich crystallization; crystallization of the alkali granite took place at higher temperatures, starting with K-rich alkali-feldspar crystallization and terminating in residual Na-rich eutectic crystallization. Parameters not available from other sources - temperature and pressure of the liquidus and solidus stages, water content, trends of crystallization - were obtained for the porphyritic and alkali granites.