Petrography and Geochemistry of Gabbroic Rock from the Penjwin Ophiolite, Kurdistan Region, Northeastern Iraq

The gabbroic rocks as a part of Zagros ophiolite are exposed in northeastern Iraq, Penjwin area. These rocks with granular to ophitic textures are widely distributed without metamorphic halos. The main minerals are plagioclase (An90-99), olivine, clinopyroxene (Wo27-47 En 45-64 Fs8-14) and orthopyroxene (Wo2 En78 Fs20) respectively based on the abundances. The major elements show a broad range of compositional variations, with SiO2 (46.2–50.9 wt. %), and low concentrations Na2O (0.15–0.62 wt. %), K2O (0.01–0.03 wt. %) and TiO2 (0.06–0.2) and high concentrations, Al2O3 (6.4–19.75 wt. %), total Fe2O3 (6.29–11.6 wt. %), MgO (9.63–24.5 wt. %), CaO (8.02–18 wt. %) and low alkali contents (Na2O + K2O = 0.16–0.65 wt. %). On Ti-V diagram, all of the gabbroic samples have Ti/V less than 10 and consequently fall in the low Ti- Island arc tholeiitic. Whole rocks chemistry shows a depletion of High field strength elements in comparison with the primitive mantle with an arched upward rare earth elements pattern, characterized by light rare earth elements depletion (La N/Sm N = 0.05–0.8) and enrichment in the High field strength elements. Whole rocks chemistry, mineral paragenesis and chemistry of these rocks are more consistent with tholeiitic magma series. Based on our findings in this research, the primary magma has been produced from the depleted mantle with a high degree of partial melting.

Petrology and geochemistry of high-Al chromitites from the MedellÍn Metaharzburgitic Unit (MMU), Colombia

The Medellin Metaharzburgitic Unit (MMU), emplaced onto the western continental margin of Pangea during Triassic time, is located in the Central Cordillera of Colombia and consists of metaharzburgites, minor metadunites and chromitite bodies (Patio Bonito and San Pedro ore deposits). The ultramafic rocks contain relicts of mantle-derived olivine, chromian spinel and minor orthopyroxene, and a later metamorphic mineral assemblage composed by tremolite, chlorite, talc, fine-grained recrystallized olivine, serpentine-group minerals, magnetite, and secondary chromian spinel, formed during the thermal evolution of the unit. The Cr# [Cr/(Cr+Al) atomic ratio] of the accessory primary chromian spinel in the metaperidotites ranges from 0.58 to 0.62 and overlaps those of supra-subduction peridotites from ophiolites. According to textural and compositional variations, the accessory chromian spinel in the metaperidotites can be classified into three groups: i) partially altered chromian spinel with an Al-rich core, ii) porous, Cr-Fe2+-enriched and Al-Mg-depleted chromian spinel, and iii) homogeneous Fe3+-rich chromian spinel. These variations can be related to superimposed medium-T metamorphism that reached amphibolite facies (ca. 600 ºC). Chromitite bodies associated with the metaperidotites have massive and semi-massive textures, and mainly consist of chromian spinel crystals, which show large unaltered cores surrounded by thin alteration rims of ferrian chromian spinel and chlorite. Chromitites are Al-rich (#Cr <0.6) and strongly depleted in platinum group elements (ΣPGE <41 ppb). The primary petrological and geochemical characteristics preserved in the metaperidotites and chromitites indicate that the MMU formed at shallow levels of a suboceanic lithospheric mantle related to a supra-subduction zone (back-arc basin/incipient arc scenario), and that the chromitites crystallized from a tholeiitic magma (back-arc basin basalt type).

U–Pb zircon geochronology and phase equilibria modelling of HP-LT rocks in the Ossa-Morena Zone, Portugal

The Ossa-Morena Zone (OMZ) has a complex geological history including both Cadomian and Variscan orogenic events. Therefore, the OMZ plays an important role in understanding the geodynamic evolution of Iberia. However, the P–T–t evolution of the OMZ is poorly documented. Here, we combine structural and metamorphic analyses with new geochronological data and geochemical analyses of mafic bodies in Ediacaran metasediments (in Iberia known as Série Negra) to constrain the geodynamic evolution of the OMZ. In the studied mafic rocks, two metamorphic stages were obtained by phase equilibria modelling: (1) a high-pressure/low-temperature event of 1.0 ± 0.1 GPa and 470–510 °C, and (2) a medium-pressure/higher-temperature event of 0.6 ± 0.2 GPa and 550–600 °C. The increase in metamorphic temperature is attributed to the intrusion of the Beja Igneous Complex (around 350 Ma) and/or the Évora Massif (around 318 Ma). New U–Pb dating on zircons from the mafic rocks with tholeiitic affinity yields an age between 815 and 790 Ma. If the zircons crystallised from the tholeiitic magma, their age would set a minimum age for the pre-Cadomian basement. The ca. 800 Ma protolith age of HP-LT tholeiitic dykes with a different metamorphic history than the host Série Negra lead us to conclude that: (1) the HP-LT mafic rocks and HP-LT marbles with dykes were included in the Ediacaran metasediments as olistoliths; (2) the blueschist metamorphism is older than 550 Ma (between ca. 790 Ma and ca. 550 Ma, e.g., Cadomian).

Origin and Geodynamic significance of opx granitoids from Bunger Hills Area, East Antarctic

&lt;p&gt;The information on magmatic orthopyroxene (opx) granitoids (charnockites) is essential for geodynamic models of continent collision, amalgamation, and postorogenic events. There is also the petrological issue - the role of the crust and mantle material in the formation of opx granitoids in orogenic and post-orogenic settings. Our research objects are three multiphase coeval plutons of the opx granitoids in the Banger Oasis, East Antarctica. Only two phases can be distinguished: the first phase comprising of silica and potassium rich middle-coarse grained qz opx monzodiorites, monzonites and granites with porphyric perthite alkali feldspar, whereas the second phase is more basic and comprises of alkali feldspar less fine-middle grained qz gabbroes and qz-opx diorites and gabbro-diorites with gabbroic and ophitic microstructure. &amp;#160;These plutons intrude granulite facies metamorphic bedrock. The age of those plutons is around 1170 &amp;#177; 10 Ma. The first phase has the age around 1170-1190 Ma, whilst the second phase has the age of 1150 1170 Ma. The interval of peak metamorphism is constrained by 1250-1170 Ma. We combine together thermodynamic modelling and geochemistry (isotope geochemistry in Sm-Nd, Rb-Sr and Pb-Pb systems, Hf and O stable isotopes data on zircons) to create a petrological model for opx granitoids formation. As a result of such modelling we are able to prove that pluthons were crystallized at grnulitic facies and dry conditions. Within the first phase of the crystal fractionation the process is traced. These phases have also different isotope characteristics. For example, the &amp;#949;(Nd)&lt;sub&gt;0&lt;/sub&gt; is around -7 to -12 for the second more basic phase and &amp;#8211; 16 to -22 for the first opx granitoids phase. It is assumed that the structures of the Banger oasis are the result of the reworking of the Yilgarn craton in the Early Proterozoic. Afterwards there was a collision and amalgamation of the supercontinent Rodinia, and at the final stage, the intrusion of opx granitoids occurred. We consider a presence of mantle material in the formation of charnockite melts. It is possible that the differentiation of tholeiitic magma and the mixing with the crustal component took place. &amp;#160;That might also go along with delamination of the thickened continental crust after the completion of collisional orogeny. Mixing with mantle material could occur at lowest levels of the crust and afterwards the mixed melt moves consequently to the higher levels and differentiates in chambers. Last phases are more enriched in mantle component according to modelling and geochemistry.&lt;/p&gt;

Physical and chemical conditions of basaltic magmatism of archipelago Franz Josef Land

As a result of mineralogical and thermobarogeochemical researches of different-age basaltic complexes of Archipelago Franz Josef Land (FJL) regular changes in time of compositions of plagioclases, clinopyroxenes and melt inclusions are established. Chemical compositions of inclusions directly testify to prevalence in Early Jurassic of plateau basaltic melts similar (according to the content of the basic components, and also trace and rare-earth elements) to typical basalt tholeiitic magma of the Siberian platform. In Early Cretaceous melts already had the enriched subalkaline character. Calculations of conditions of magma generation, spent on the basis of the data on melt inclusions, have shown evolution from Early Jurassic to Early Cretaceous (with allocation of three peaks of magmatic activity: 192.2±2.8, 157.4±3.5 and 131.5±0.8 million years) depths and temperatures (accordingly: 70-110 km and to 120 km, 1430-1580°С; 60-110 km, 1390-1580°С; 50-140 km, 1350-1690°С) of mantle melting with formation of deep sources of the FJL magmas.

Rapid cooling history of a Neotethyan ophiolite: Evidence for contemporaneous subduction initiation and metamorphic sole formation

The Beyşehir-Hoyran Nappes, including Mesozoic carbonate platform rocks, deep-sea sediments, and ophiolite-related units, crop out extensively on the western limb of the Isparta Angle in the Central Taurides, Turkey. The ophiolite-related rocks are represented by variably serpentinized harzburgitic mantle tectonites, tectonically underlain by a subophiolitic metamorphic sole and mélange. The harzburgitic mantle tectonites and metamorphic sole are intruded by undeformed isolated dikes. Protoliths of the metamorphic sole are similar to within-plate alkali basalts and associated sediments. The isolated dikes were geochemically derived mainly from tholeiitic magma and, to a lesser extent, from alkaline magma. Five isolated dike samples yielded U-Pb ages ranging from 90.8 ± 1.6 Ma to 87.6 ± 2.1 Ma (zircon) and from 102.3 ± 7.4 Ma to 87.5 ± 7.9 Ma (titanite). Seven amphibolite samples yielded U-Pb age ranges of 91.1 ± 2.1–88.85 ± 1.0 Ma (zircon) and 94.0 ± 4.8–90.0 ± 9.4 Ma (titanite) and a 40Ar-39Ar age range of 93.7 ± 0.3–91.4 ± 0.4 Ma (hornblende). U-Pb and 40Ar-39Ar ages of mineral phases with different closure temperatures (∼900–500 °C) from the isolated dikes and metamorphic sole rocks are almost identical and overlapping within 1σ, suggesting that both the magmatic growth of oceanic crust and formation of metamorphic sole were contemporaneous and cooled very rapidly. Hence, all the data should be interpreted as the crystallization ages of the ophiolite and metamorphic sole pair. Genesis of suprasubduction zone–type oceanic crust, genesis and exhumation of the metamorphic sole, and postmetamorphic dike emplacement within the Inner Tauride Ocean can be best explained by subduction initiation and rollback processes during the Late Cretaceous based on petrological and geochronological data obtained from the ophiolitic rocks of the Beyşehir-Hoyran Nappes.

Petrology, mineral chemistry, and geochemistry of Late Triassic Ni–Cu ore-bearing mafic–ultramafic intrusions, Hongqiling, northeastern China: petrogenesis and tectonic implications

The Hongqiling magmatic Ni–Cu sulfide deposit, situated on the southern margin of the eastern Central Asian Orogenic Belt (CAOB), is composed of over 30 mafic–ultramafic intrusions. These ore-bearing intrusions are composed mainly of harzburgite, lherzolite, websterite, orthopyroxenite, and norite (gabbro). The constituent minerals are olivine, diopside, bronzite, calcic-hornblende, plagioclase, and spinel with orthopyroxene as a dominant mineral in these intrusions. These ore-bearing intrusions are not Alaskan-type complexes. Spinel and clinopyroxene both exhibit different chemical compositions from those in the Alaskan-type complexes. The rocks that make up the intrusions have high contents of MgO (average value = 25.20 wt.%) and low TiO2 (average value = 0.58 wt.%). The high MgO contents of the minerals and the high Mg# (71) of the calculated melt in equilibrium with olivine demonstrate that the parental magma of the Hongqiling mafic–ultramafic intrusions was a high-Mg tholeiitic magma. The Hongqiling ore-bearing mafic–ultramafic intrusions and the calculated “trapped liquids” for the olivine-orthopyroxene cumulate rocks are all enriched in large-ion lithophile elements and depleted in high field strength elements. The Ce/Pb, Ta/La, Th/Yb, and (La/Sm)PM values and the depletion of Nb and Ta suggest that the magma experienced crustal contamination. The Hongqiling ore-bearing intrusions display many similarities with mafic–ultramafic intrusions that formed in a post-collisional extensional environment in the western CAOB (e.g., Huangshanxi). Common features include their whole-rock compositions and mineral chemistry. Combined with the evolutionary history of the eastern segment of the CAOB, we believe that the Late Triassic Hongqiling mafic–ultramafic intrusions formed in a post-collisional extensional environment.

Mineralogy and Geochemistry of Titaniferous Gabbros of Ophiolitic Fanouj Zone (Sistan & Baluchestan, Iran)

<p><span lang="EN-US">Ophiolite complex in the west of Fanuj is 200 Km south west of Iranshahr in Sistan and Baluchestan province. This ophiolite complex lies in the uplift zone of the oceanic crust of Oman between Makran and Fanuj faults. Ophiolite of the west part of Fanuj is consisted of three parts including gabbro, diabase dikes and small quantity microdiorite masses. Ilmenite is the main mineral of titanium which along with magnetite has been formed independently or inter-crystalline way after crystallization of plagioclase, pyroxene and often along with amphibole in gabbro rocks. The formation of the broad gabbro masses which is associated with plagioclase and pyroxene crystallization in High Oxygen fugacity condition formed a fluid rich in iron and titanium during the formation of ferro gabbro rocks as the main host of the ilminite reserves. Gradual crystallization process and decrease in compatible elements such as </span><span lang="EN-US">Cr, Ni, Mg and increase in incompatible elements such as Mn</span><span lang="FA" dir="RTL">،</span><span lang="EN-US"> Na</span><span lang="FA" dir="RTL">،</span><span lang="EN-US"> Ti from the bottom to the upper parts of ophilite complex shows that </span><span lang="EN-US">the formation of the complex has been occurred through the process of crystal fractionation from a tholeiitic magma which is rich in titanium.</span></p>

EVALUATION OF COPPER DEPOSITS PROSPECT IN WAI WAJO AREA OF SIKKA REGENCY, EAST NUSA TENGGARA PROVINCE

Lowo Deba prospect in Sikka Regency, East Nusa Tenggara Province shows significant evidences for copper deposit. The prospect is discovered by joint cooperation activity between Directorate of Mineral Resources Inventory (DMRI) and Korea Resources Corporation (KORES) in the systematic exploration program. The evaluation based on the quantitative analysis of rock and mineral characteristics as well as geologic mapping, petrography, mineragraphy, fluid inclusion, spectra analysis (PIMA), geochemical and geophysical data. The geology of the prospect area consists of Miocene volcanics of Kiro Formation and Tanahau Formation, intrusion of granodiorite and Quaternary volcanics. The volcanic rock shows the characteristic of tholeiitic magma. The predominant system of lineaments in the prospect area tends to be NE-SW trend. This fault structure appears to have closely relationship with the mineralization in Lowo Deba prospect. The mineralization and alteration outcrops appear to be structural controlled to form epithermal deposit type. Most of the mineralizations are hosted by phyllic – argillic altered andesitic to dacitic tuff which is intruded by granodiorite. Rock samples indicate the mineralization type is quartz vein containing chalcopyrite, galena, sphalerite, covellite and pyrite. The best grade revealed from these altered rocks of 6,980 ppm Cu and 50 ppb Au, and from quartz vein of 4,868 ppm Cu and 57 ppb Au. Mineralization stages evolved from initial higher temperatures (> 320° C) to later lower temperatures (near 170° C). Soil geochemical analysis identify two zones of combined anomaly i.e. Au-Cu-Mo and AgPb-Zn. Those anomalies are concentrated in the phyllic and argillic altered andesitic tuff. These soil anomaly coincide with IP anomalies which are found in electrode separation index of n=5 and n=7 in line WA7 with chargeability value up to 405.7 Msec and resistivity value of 37.7 Ohm-m. In general high chargeability and low resistivity anomalies are developed in the direction of southwest to northeast and still open to the northeast. The high chargeability value allows to predict the occurrence of copper deposits potential. Some bore holes are proposed for the next survey to confirm the presence of new copper deposits in the prospect area.