Titanite Research Articles

Trace and Rare Earth Element Compositions of Lawsonite as a Chemical Tracer of Metamorphic Processes in Subduction Zones

AbstractLawsonite is a major host mineral of trace elements (TEs; e.g. REE, Sr, Pb, U, Th) and H2O in various rock types (metabasite, metasediment, metasomatite) over a wide range of depths in subduction zones. Consequently, the composition of lawsonite is a useful archive to track chemical exchanges that occurred during subduction and/or exhumation, as recorded in high-pressure/low-temperature (HP/LT) terranes. This study provides an extensive dataset of major element and TE compositions of lawsonite in HP/LT rocks from two mélanges (Franciscan/USA; Rio San Juan/Dominican Republic), two structurally coherent terranes (Tavşanlı/Turkey; Alpine Corsica/France), and the eclogite blocks of the Pinchi Lake/Canada complex. Bulk major and TE compositions were also determined for lawsonite-bearing host rocks to understand petrogenesis and assess compositional evolution. Most analyzed mélange and coherent-terrane metabasalts have normal mid-ocean ridge/back-arc basin basalt signatures and they preserve compositional evidence supporting interactions with (meta)sediment ± metagabbro/serpentinite (e.g. LILE/LREE enrichments; Ni/Cr enrichments). Most lawsonite grains analyzed are compositionally zoned in transition-metal elements (Fe, Ti, Cr), other TEs (e.g. Sr, Pb), and/or REE, with some grains showing compositional variations that correlate with zoning patterns (e.g. Ti-sector zoning, core-to-rim zoning in Fe, Cr-oscillatory zoning). Our results suggest that compositional variations in lawsonite formed in response to crystallographic control (in Ti-sector zoning), fluid–host rock interactions, modal changes in minerals, and/or element fractionation with coexisting minerals that compete for TEs (e.g. epidote, titanite). The Cr/V and Sr/Pb ratios of lawsonite are useful to track the compositional influence of serpentinite/metagabbro (high Cr/V) and quartz-rich (meta)sediment (low Sr/Pb). Therefore, lawsonite trace and rare earth element compositions effectively record element redistribution driven by metamorphic reactions and fluid–rock interactions that occurred in subduction systems.

Host rock peculiarities and influence of major structures on gold and base metal sulfide mineralization in northern Pakistan

For decades, the streams and rivers in northern areas of Pakistan are being explored for gold but the source rock for primary gold is yet to be located. Recent geological surveys have identified several areas for follow-up study for Cu-Au mineralization in Chitral and Gilgit-Baltistan regions. The rocks exposed at various localities are variably altered and/ or mineralized and intensely deformed, which mostly include diorite, granodiorite, greenschists, limestones and undeformed volcanic rocks and granitoids of the Kohistan island arc. The results of petrographic and X-ray diffraction (XRD) analyses of a variety of representative rock samples from a number sites have revealed that mineralization in the Chitral and Gilgit-Baltistan regions is dominantly in the form of pyrite, tetrahedrite, chalcopyrite and galena with subordinate amounts of magnetite, malachite and azurite. The associated/ gangue minerals include albite, quartz, actinolite, biotite, chlorite, epidote, calcite, garnet, illite and titanite (sphene). Diffraction patterns of glycolated samples did not show the existence of swelling clay (e.g., smectite). Sericitic, chloritic and carbonatic alterations have been observed in the studied altered rocks. Mass balance calculations indicate that most of the sulfide-bearing samples are enriched in Cu, Au, Sb, As and Pb and depleted in the rest of the metals reflecting differences in elements mobility during the ore-forming processes. Some of the mineralized rocks especially limestone have experienced a significant volume change due to mobilization of some of the major element oxides e.g. CaO, Fe2O3, SiO2 and ore-forming components e.g. Cu and Pb. The mineralization is of epithermal type in most of the investigated sites, however a few areas show ore formation though orogenic processes and very rarely the ore deposit displays features of the volcanogenic massive sulfide type. Some of the areas are quite promising with respect to their ore element contents and the highly mineralized zones lie in close proximity to major structures in the region. Besides, results from the current study indicate that the mineralization shows close spatial association and hence a strong genetic link with strike slip faults especially where they bend and merge together.

Melt-rock interaction between granitic pegmatites and hosting amphibolites from the Chiavenna Ophiolitic Unit (Tanno Pegmatitic Field, Central Alps, North Italy)

The Tanno pegmatitic field, placed southward of Chiavenna (Central Alps, Sondrio, Italy), develops a large number of subplanar dykes that crosscut the Chiavenna Unit, an ophiolitic complex mainly composed, in the study area, of amphibolite rocks. This study focuses on the contact between a pegmatitic dyke and the amphibolitic country rock. We distinguished four zones across the contact: I) inner amphibolite, II) contact amphibolite, III) contact pegmatite, IV) inner pegmatite. The inner amphibolite, not affected by melt-rock interaction, is composed of amphibole, phlogopite, ilmenite, titanite and rutile. Two amphibole generations occur, both of them showing a patchy compositional zoning. Amphibole I are Mg-hornblende, whereas Amphibole II have a pargasitic composition. The contact amphibolite shows an enrichment of mica belonging to the phlogopite-biotite series, titanite and the presence of fluorapatite and plagioclase (Ab45-60), that is absent in the inner amphibolite. Close to the contact, amphiboles display no zoning and gain an Mg-horneblenditic composition. The contact pegmatite has quartz, albitic plagioclase, garnet (almandine-spessartine series), muscovite, K-feldspar and fluorapatite. It shows a comb texture, with elongation of plagioclase crystals normal to the contact itself. Far from the contact, the inner pegmatite has an increasing grain-size and a less organized texture. In this zone several accessory phases occur, including gahnite, columbite-(Fe), monazite-(Ce), xenotime-(Y), uraninite and betafite. Whole rock analyses suggest that a chemical exchange, concerning both major elements and trace elements, occurred between the pegmatitic melt and the hosting amphibolite. A considerable increase of SiO2, Na2O and, to a lesser extent, of Al2O3 is observed from the amphibolite towards the pegmatite; K2O and CaO show a decrease at the same extent. The REE pattern in the pegmatite highlights an enrichment in HREE at the contact. Mineral chemistry confirms this trend with variations observable in plagioclase, gradually more albitic from the amphibolite to the pegmatite. Mineralogical characters and geochemical features allow to classify the Tanno pegmatite in the LCT (Lithium, Cesium, Tantalium) family. Based on the metamorphic peak conditions reported from the Lepontine Dome the ambient conditions during pegmatite intrusion were ca. 550°C and 5 kbar. The reduced thermal difference between pegmatite and wall rock explains the diffuse contact observed by X-ray micro-computed tomography. The collected data suggest a chemical interaction between melt and wall rock, according to the following reaction taking place in the amphibolite Amphibole I + Amphibole II + Ilmenite + Pegmatitic melt → Amphibole III + Plagioclase + Phlogopite + Titanite + Fluorapatite

Titanite (Sphene) Inclusions in Ruby Identified by Infrared Spectroscopy

Titanite (Sphene) Inclusions in Ruby Identified by Infrared Spectroscopy

Titanite-centered ocellar texture: A petrological tool to unveil the mechanism facilitating magma mixing

The titanite-centered ocellar texture is a rarely observed texture from magma mixing and mingling zones. This work provides a synthesis of petrographical observations and mineral-chemical data to understand the genesis of this texture. The rock with titanite ocelli is from the mafic-felsic interaction zone of the Nimchak Granite Pluton (NGP) of Chotanagpur Granite Gneiss Complex (CGGC) of Eastern India. Interpretations reveal that when mafic (basaltic) magma intrudes a crystallizing felsic (granite) magma chamber the first interaction that takes place between the two phases is diffusion of heat from the relatively hotter mafic magma to the colder felsic magma followed by diffusion of elements. When thermal equilibrium is reached between the two magmas the rheological contrasts between the two phases gets drastically reduced, allowing the felsic melt to back-vein the mafic magma. The influx of felsic melt results in breakdown of minerals like amphibole and biotite in the mafic system resulting in liquids of titanite composition. These liquids get incorporated into the incoming felsic melt as an immiscible phase and flow with it. The felsic melt and the immiscible titanite-liquid occupy the void spaces left behind by escaping gases/volatiles in the mafic system ultimately forming rounded titanite ocelli.

U-Th-Pb “multi-phase” approach to the study of crystalline basement: application to the northernmost sector of the Ivrea-Verbano Zone (Alps)

In situ U-Pb geochronology was carried out on amphibolites and siliciclastic metasediments of the Kinzigite Formation exposed in the northernmost sector of the Ivrea-Verbano Zone (Finero area). The aim is to shed light on the tectono-metamorphic evolution of this intermediate-lower crustal section and its bearing with the evolution of the southern and better known sectors of the IVZ. Based on field observation and petrography a metamorphic gradient gently increasing from amphibolite to upper amphibolite facies (from SE to NW) characterizes the whole metamorphic sequence. Metapelites consist mainly of biotite, quartz, plagioclase, garnet, and sillimanite; muscovite progressively disappears as K-feldspar appears and becomes abundant. Amphibolites are made of green-brown hornblende and plagioclase and may contain clinopyroxene defining thin layers together with plagioclase and titanite. Both metapelites and amphibolites show mylonitic deformation which is more intense towards NW, i.e. towards the lower structural levels. The mylonitic deformation strongly affected the lower crustal metabasic rocks of External Gabbro unit (Finero Mafic Complex). Zircon, monazite and titanite U-Pb geochronology was carried out with laser ablation (LA)-ICP-MS on amphibolites, migmatitic paragneiss and mafic granulites occurring as slivers of the Kinzigite Formation in the External Gabbro unit of the Finero Mafic Complex. The multi-chronological approach allowed recognizing three discrete tectono-metamorphic events, at Permian, Triassic and Jurassic. Zircon and monazite yielded Permian ages suggesting (re)crystallization during an high temperature event characterized by both metamorphism and magmatism. Titanite dating provided Triassic and Jurassic ages that were interpreted as U-Pb resetting ages. A Triassic perturbation of the U-Pb system was also recorded by zircon and monazite as rare domains. The tectono-metamorphic reconstruction of the evolution of the northernmost IVZ, as revealed by the new geochronological data, is only partially in agreement with the temperature-time evolutions depicted for the southern sectors of the IVZ. Permian ages indicating magmatism and high temperature metamorphism are common throughout the IVZ, as well as the Jurassic ages related to local thermal pulses and tectonic activity. Conversely, the occurrence of well-constrained Triassic ages is in fact peculiar of the Finero area. Two possible explanations may account for this Triassic event: Triassic ages are possibly related to the thermal effect and fluid circulation during the emplacement of the External Gabbro unit; or alternatively, they are the response to the ductile deformation largely recognized in the whole area. This study is a further evidence of the necessity of approaching crystalline basement with multiple geochronometers in order to unravel the complete tectono-metamorphic evolution.

Geochemical heterogeneity and reconstruction of the source of Upper Jurassic sandstone in the western part of West Siberia

The Shaim region located in the western part of the West Siberian Megabasin is the most wellstudied in this large and very important area. The crystalline basement is relatively shallow (1.5-2.2 km) there. A complex geological and geophysical study of this area was performed (1), and a geological map (1 : 200 000) of the preJurassic basement was compiled; a fragment of it is shown in Fig. 1. Two large structures are mapped there: the Danilov graben mostly composed of cenotypal basalt and rarely rhyolite of the Triassic age and the Shaim-Kusnetsov megaanticlinorium represented by a chain of Late Carboniferous-Early Permian monzodiorite-granosyenite massifs and their metamorphic schist frame (also known as a "granite-schist axis"). The preJurassic basement is overlain by the Upper Jurassic Vogulkinskaya Forma� tion mostly composed of sandstone. Within the Danilov graben, this formation is revealed by holes in the Tal'nikovaya, Symor'yakhskaya, Danilovskaya, and SeveroDanilovskaya areas, where it occurs on the Triassic rhyolite-basalt complexes. The same sedi� ments are observed on the territory of the "granite- schist axis" within the Tolumskaya, Teterevskaya, Mortym'yaTeterevskaya, and Trekhozernaya areas. In this study, we report a set of the chemical and geochemical analyses only from the Danilovskaya, Tal'nikovaya, Teterevskaya, and Trekhozernaya areas. The Vogulkinskaya Formation in the western part of West Siberia is mostly composed of sandstone (including glauconiterich), as well as gritstone, con� glomerate, rarely argillite, calcic sandstone, and orga� nogenic detrital limestone, which are almost not observed in other formations of the sedimentary cover in West Siberia (2). The thickness of the Vogulkinskaya Formation reaches 70 m. It is oilbearing and replaced by argillite of the Abalakskaya Formation. Sandstones from the Vogulkinskaya Formation are visually indistinguishable from each other; they have a lightgray up to brownish color and are almost always finegranular with a clay-carbonate cement. The mineralogy of sandstones of the Vogulkinskaya For� mation is considered for the area of the "granite- schist axis." They are composed of quartz and plagio� clase fragments; cement is clay-carbonate. Carbonate prevails, and its composition corresponds to calcite with admixtures of MgO (up to 1.07 wt %) and FeO (up to 0.79 wt %); sometimes the portion of carbonate reaches 50-60%, which allows us to attribute these rocks to sandy limestone. Glauconite, mica, plagio� clase, rutile, pyrite, and tourmaline are registered among the minor and accessory minerals. Quartz forms isometric grains with a size up to 1 mm. Albite is represented by tabular individuals with a size of 0. n mm. Mica often forms individual laths and aggregates, usually deformed. According to the composition, it corresponds to the muscovite-aluminoseladonite series (most analyses plot in the muscovite field) and contains up to 6% of the paragonite endmember. Tourmaline is characterized by individual wellformed prismatic grains with a size up to 0.5 mm; its chemical composition corresponds to that of dravite (48-50% of endmember) with a high concentration of foitite and magnesiofoitite (in total, up to 30-35%), olenite (up to 12%), and uvite (up to 10%). Rutile does not contain impurities and sometimes is replaced by titan� ite from the margins.

CHARACTERISTICS OF HEAVY MINERALS IN PEARL RIVER SEDIMENTS AND THEIR IMPLICATIONS FOR PROVENANCE

Heavy minerals in the Pearl River sediments have excellent correlation with their source rocks.Obvious differences in heavy minerals assemblages and their diagnostic minerals have been studied in different branches of the River.The source of the river deposits can be divided into three provinces from west to east on the basis of heavy minerals assemblage types,mineral index(ATi,ZTi,ZTR) values and their correlation.The western province includes the upper reaches of the Xijiang River,where occurs a magnetite-ilmenite-zircon-leucoxene-apatite assemblage characterized by magnetite,ilmenite,apatite and chromite,indicating a provenance dominated by carbonate,with some metamorphic and basic rocks,and scarce ultrabasic and acid rocks.The middle province is located in the lower reaches of the Xijiang River,which is featured by a zircon-ilmenite-magnetite-tourmaline-leucoxene-epidote assemblage,characterized by pyroxene,leucoxene,zircon and epidote,indicating a provenance of clastic rocks and other sedimentary rocks with some metamorphic,basic and acid igneous rocks,as a mixture of local sources and the heavy minerals from upper reaches.The eastern province is the source area of the Dongjiang and Beijiang Rivers dominated by the assemblage of hornblende-tourmaline-magnetite-ilmenite-epidote-garnet characterized by hornblende,tourmaline,garnet,titanite and sillimanite,indicating a provenance of acid rocks with some metamorphic and small amount of sedimentary rocks.The results demonstrate that the characteristics of heavy minerals assemblages are useful tools to trace the provenance evolution of the Pearl River,and of significance in revealing the erosion-transportation-sedimentation pattern in the Pearl River region for source-sink comparison and analysis.

Aluminum-fluorine sphene (Titanite) as an indicator of fluorine fluid

Aluminum-fluorine sphene (Titanite) as an indicator of fluorine fluid

Mineralogical, IR-spectral and geochemical monitoring of hydrothermal alteration in a deformed and metamorphosed Jurassic VMS deposit at Arroyo Rojo, Tierra del Fuego, Argentina

Fil: Biel, C.. Universidad de Zaragoza; Espana. Productos Minerales para la Industria S.A.; Espana

Karst bauxites in the Campania Apennines (southern Italy): a new approach

In this study new data on two bauxite districts in the Campania region (southern Italy) are reported: the Matese Mts. and the Caserta province, exploited in the first part of the XX century. The nature and distribution of diagenetic and detrital mineral phases were investigated by means of transmitted-light and scanning electron (SEM) microscopy, X-ray powder diffraction (XRPD) and energy dispersive spectroscopic microanalysis (EDS), whole-rock geochemical analyses (ICP-OES and ICP-MS), complemented by preliminary QEMSCAN ® investigation. The textures of the bauxite ore range between oolitic and oolitic-conglomeratic and arenitic. Boehmite is the most abundant phase, while other Al-bearing phases (gibbsite and diaspore) are very subordinate. The Fe-minerals hematite, goethite and lepidocrocite occur, and Ti-minerals anatase and rutile are ubiquitous. Among clay minerals, kaolinite is prevailing at the Regia Piana (Matese Mts.) and illite-montmorillonite in the Caserta province. Most recorded trace minerals are quartz, calcite, zircon and monazite. Small clusters of not previously detected qandilite [(Mg, Fe 2+ ) 2 (Ti, Fe 3+ , Al) O 4 ], and of hercynite-type spinels also occur. By means of QEMSCAN ® it has been possible to better recognize some diagenetic textures (e.g. mainly matrix- or ooids-supported bauxite, the clay/Al-hydroxides distribution etc.) and to detect other detrital minerals (feldspar, muscovite, olivine, titanite and possibly a serpentine/talc-like phase). A similar detrital mineral association has been found also in the Aptian “Orbitoline ” marls, which are marine sediments supposed to be the non-weathered equivalent of bauxites. Very detailed data about major, minor and trace element (comprising “bauxitophile ” and REEs) concentrations and some significant geochemical ratios are reported for the bauxite samples, and a new interpretation on the possible source of the parent material has been proposed. The detrital heavy mineral association may suggest not only a windblown volcanic source material (Dinarides explosive volcanism?), as hypothesized in literature, but also a partial origin from an exposed terrain. The exact nature and paleogeographic position of this source could not be determined by chemical analyses of major and trace elements (including REE), Eu/Eu* and TiO 2 /Al 2 O 3 ratios and Ni-Cr contents. However, due to the isolated position of the Appennine carbonate platform during the Cretaceous, the paleogeographic model precludes any possible fluviomarine transport for the source material (windblown?) of the bauxites.

METAMORPHIC HISTORY OF ECLOGITIC METAGABBRO BLOCKS FROM A TECTONIC MÉLANGE IN THE VOLTRI MASSIF, LIGURIAN ALPS, ITALY

Iron/titanium-rich metagabbros, derived from the Beigua serpentinite unit, were collected from a tectonic melange along the contact between the Beigua serpentinite unit and the underlying Voltri-Rossiglione calcschist unit of the Voltri Group in the Ligurian Alps of northern Italy. Petrographic study and microchemical analysis have been undertaken to unravel the details of their metamorphic history. The metagabbros formed during Jurassic oceanisation in the Piedmont-Ligurian realm, and show local evidence of rodingitisation during ocean-floor metamorphism. Together with the country rock serpentinites, they were subjected to high-pressure metamorphism during Alpine subduction and eventual collision. The high-pressure assemblage in the metagabbro blocks consists of garnet, omphacite, glaucophane, and locally white mica, rutile or titanite. Peak metamorphic conditions, estimated using garnet-omphacite-phengite thermobarometry, were 500 ± 50°C and 17.5 ± 0.5 kbar, i.e. higher peak pressures than previously estimated for these rocks. The rocks cooled continuously during decompression. Exhumation initially proceeded along a low-AET/AEP trajectory, followed by final exhumation along a higher gradient close to that of a continental geotherm. The Voltri Massif had arrived at the Earth’s surface by 34 million years ago, because exhumed rocks of the massif are covered by early Oligocene continental scree breccias and conglomerates. We propose a combination of buoyancy of the serpentinites in the Beigua unit and corner flow in the orogenic wedge on top of the subducting Piedmont- Ligurian oceanic lithosphere as a plausible mechanism to drive exhumation of the high-pressure rocks of the Voltri Massif.

The Occurrence of Wollastonite and Titanite

The Occurrence of Wollastonite and Titanite

Scandium titanite and scandium vanadite

Scandium titanite and scandium vanadite

Notes on alunite, psilomlanite, and titanite

Notes on alunite, psilomlanite, and titanite