Detrital Tourmaline Research Articles

Provenance and paleodrainage patterns of Upper Jurassic and Lower Cretaceous synrift sandstones in the Flemish Pass Basin, offshore Newfoundland, east coast of Canada

Upper Jurassic to Lower Cretaceous synrift sandstones from two industry exploratory wells in the Flemish Pass Basin were studied for provenance using heavy mineral proxies. These sandstones were deposited during the North Atlantic rifting stage, at which time rifting intensified between Iberia and the Grand Banks. Several heavy mineral methods were used, including in-situ U-Pb geochronology and morphological and chemical analysis of detrital zircons, chemical discrimination of detrital tourmalines, and heavy mineral ratios.Clastic bed-load material entering the northern Flemish Pass Basin during the Tithonian to Berriasian was connected to transport systems reaching west, as far as 400 to 500 km (249–311 mi). Source areas to the west included igneous rocks and associated cover sequences of the Avalon zone, as well as the magmatic rocks, metasedimentary rocks, and associated cover sequences present in the Central mobile belt. The eastward-directed input of bed-load material into the basin is considered to have resulted in the concentration of sandstone units along its western margin, with deteriorating reservoir grade toward the east. Given the regional extent of drainage systems, it is likely that similar constraints apply to equivalent sandstones in the adjacent East Orphan Basin.By the Valanginian–Barremian, paleodrainage orientations had switched and bed-load material began to enter the Flemish Pass Basin from more proximal areas to the southeast with the Avalon zone basement.Overall, no evidence exists to support sediment sourcing from the Iberian margin or the Flemish Cap-Galicia Bank continental fragment to the east, and material from these areas is instead interpreted to have been shed into the incipient Atlantic Ocean or Bay of Biscay. Also, no evidence exists to support sourcing from Grenville basement farther to the west, implying that a drainage divide may have existed somewhere between central and western Newfoundland, west of which material was presumably being transported to the south or southwest.

Mineral chemistry and chemical zoning in tourmalines, Pampa del Tamboreo, San Luis, Argentina

Tourmalinites that are distally associated with tungsten deposits of the Pampa del Tamboreo area, San Luis, Argentina, contain tourmalines retaining evidence for its origin and evolution. Tourmaline grains uncommonly contain small grains of detrital tourmaline. Analysis of a single detrital tourmaline grain reveals that it is a Ca-rich “oxy-dravite”. Proximal to the detrital cores there are inner domains of asymmetric tourmaline overgrowths that developed during low grade metamorphism. Volumetrically dominant tourmaline overgrowths in the outer domain are concentrically zoned aluminous dravite and “oxy-dravite” with Al/(Al + Fe + Mg) = 0.71–0.74 and Mg/(Mg + Fe) = 0.64–0.71. Variability of Al is primarily controlled by the deprotonation substitution R + OH − = Al + O 2− (where R = Fe + Mg), and is a function of the activity of H 2O. A likely evolutionary scenario is one in which volcanogenic material is altered by hydrothermal fluids in the sea floor resulting in an aluminous and magnesian residuum. With further hydrothermal circulation and incipient metamorphism, boron-rich fluids are expelled from metasedimentary and metavolcanic basement rocks and develop Mg-rich tourmalinites in the aluminous, magnesian host rocks. The tourmalinization process occurs over a range of metamorphic conditions and with fluids of variable activity of H 2O.

The texture and composition of tourmaline in metasediments of the Sinai, Egypt: Implications for the tectono-metamorphic evolution of the Pan-African basement

AbstractAccessory tourmaline in metasediments from the Sinai crystalline basement exhibits textural and chemical signatures that relate to the evolution of regional metamorphism and deformation during the Pan-African orogeny and testifies to differentP-Tpath segments. Tourmaline inclusions in various porphyroblasts were formed during the prograde phase of metamorphism; acicular to prismatic crystals in the matrix, oriented sub-parallel to, and enveloped by, the main foliation crystallized syntectonically under prograde and peak metamorphic conditions; tourmaline cross-cutting the main foliation may have formed just after the peak or during the retrograde phase of metamorphism. Some of the cores in tourmaline crystals, showing different colours, are interpreted as former detrital grains. The abundance of tourmaline decreases with increasing peak metamorphic conditions. The tourmaline investigated belongs to the schorl-dravitessgroup, generally withXMgof 0.42–0.73 and XCa= Ca/(Ca+Na+K+□) of 0.02–0.24, typical of tourmalines in metapelites and metapsammites; whereas detrital cores have been derived from various sources, including former tourmaline-quartz and pre-existing high-metamorphic rocks. Tourmaline of the Sinai metasediments was formed during metamorphism of the sedimentary precursors, essentially in a closed system, where clay minerals and organic matter, together with detrital tourmaline, served as the source of boron. Although a metamorphic facies should be defined by characteristic mineral assemblages present in metamorphic rocks, tourmaline chemistry is a good monitor ofP-Tconditions in the metapelites and semi-metapelites investigated, showing an increase inXMgwith increasing metamorphic grade, whereXturMg= 0.60 distinguishes between greenschist and lower-amphibolite facies, whileXturMg= 0.65 could distinguish lower- from middle- to upper-amphibolite facies. The results of tourmaline-biotite geothermometry compare well with our former temperature estimates using conventional geothermometry and phase-diagram modelling.

Epigenetic to low-grade tourmaline in the Gdoumont metaconglomerates (Belgium): A sensitive probe of its chemical environment of formation

This study reports the first observation and compositional data of tourmaline overgrowths in the post-Caledonian basal Gdoumont conglomerates of the Belgian part of the Rhenohercynian basin. Authigenic tourmaline occurs as monopolar hemimorphic and bipolar asymmetrical foitite overgrowths within fractures and along the margins of detrital tourmaline grains and tourmalinite pebbles. Formulae calculated from electron-microprobe analyses reveal high amounts of vacancies in the X-site (61 to 84%), placing this tourmaline amongst the most alkali-deficient tourmaline recorded to date. Besides the alkali-deficiency, Gdoumont overgrowths are characterized by high Al, low Na and Ca, and low-to-moderate Mg/(Fe + Mg) ratios. These characteristics reflect the composition of the host conglomerates and suggest local derivation of the chemical components. Slightly differing zoning patterns (sample scale) and differences between localities (regional scale) indicate heterogeneity of the low-grade host rock. Host tourmaline grains as well as tourmaline occurring in quartz-veins crosscutting the Gdoumont metasediments have distinctly different compositions. The absence of discontinuous zoning suggests growth of the authigenic tourmaline in just one stage. It is most likely that tourmaline formed from boron released by metamorphic breakdown of detrital minerals, e.g. illite and/or K-feldspar. Based on their crystal chemistry and the observed optical properties, the overgrowths must have developed during diagenetic to lower-greenschist facies conditions. Scarce concurrency of bipolar overgrowths, isolated neoblasts and cryptocrystalline nests of tourmaline indicates limited growth until middle-greenschists facies conditions.

Provenance of Carboniferous sedimentary rocks in the northern margin of Dabie Mountains, central China and the tectonic significance: constraints from trace elements, mineral chemistry and SHRIMP dating of zircons

A suite of slightly metamorphosed Carboniferous sedimentary strata occurs in the northern margin of the Dabie Mountains, central China. It consists, in ascending order, of the upper Huayuanqiang Formation (C 1), the Yangshan Formation (C 1), the Daorenchong Formation (C 1–2), the most widely distributed Huyoufang Formation (C 2) and the Yangxiaozhuang Formation (C 2). The provenance of the Carboniferous sedimentary rocks is constrained by the integration of trace elements, detrital mineral chemistry and sensitive high resolution ion microprobe (SHRIMP) dating of detrital zircons, which can help to understand the connection between the provenance and the Paleozoic tectonic evolution of the Qinling–Dabie Orogen. The trace element compositions indicate that the source terrain was probably a continental island arc. Detrital tourmalines were mainly derived from aluminous and Al-poor metapelites and metapsammites, and some are sourced from Li-poor granitoids, pegmatites and aplites. Detrital garnets, found only in the uppermost Huyoufang Formation, are almandine and Mn-almandine garnets, indicating probable sources mainly from garnetiferous schists, and partly from granitoid rocks. The detrital white K-micas are muscovitic in the Huayuanqiang, Daorenchong and Huyoufang Formations, and phengitic with Si contents (p.f.u.) from 3.20 up to max. 3.47–3.53 in the uppermost Huyoufang and the Yangxiaozhuang Formations, a meta-sedimentary source. Major components in the detrital zircon age structure for the Huyoufang Formation range from 506 to 363 Ma, centering on ∼400 and ∼480 Ma, which is characteristic of the Qinling and Erlangping Groups in the Qinling and Tongbai Mountains, central China. Evidently, the major source of the Carboniferous sedimentary rocks in the northern margin of Dabie Mountains was from the southern margin of the Sino-Korean Craton represented by the Qinling and Erlangping Groups. The source area was an island-arc system during the Early Paleozoic that collided with the Sino-Korea plate towards the end of the Early Paleozoic or during the Devonian. A prominent feature in the detrital zircon age structure of the Huyoufang Formation is the Neoproterozoic detritus, which could be derived only from the Yangtze Craton. Reasonable interpretation of the two distinct source materials for the Huyoufang Formation is that the two plates were juxtaposed through collision before the late Carboniferous.

飛騨外縁帯上広瀬層にみられる電気石の産状と化学組成

Tourmaline-bearing hydrothermal veins and metamorphic tourmalines occur in the Kamihirose Formation, circum-Hida terrane. The Kamihirose Formation was intruded by the Funatsu granitic rocks and underwent the contact metamorphism. Two types of tourmaline-bearing hydrothermal veins were distinguished: (1) tourmaline vein, which consists mostly of tourmaline with quartz and minor apatite; (2) potassium feldspar vein, which consists mostly of orthoclase with quartz, plagioclase and acicular tourmaline. Metamorphic tourmalines are found in sandstone and tonalite porphyry and tuffaceous sandstone clast of conglomerate. There are three types of sandstones that yield metamorphic tourmalines: black, white and acidic tuffaceous sandstones. In the black sandstone, the metamorphic tourmalines occur in shale fragments and occur as overgrowth on detrital tourmalines, whereas, in the white sandstone, those occur in acidic tuff fragments. In the acidic tuffaceous sandstone, metamorphic tourmalines occur in the tuffaceous matrix. The electron-microprobe analyses of tourmalines revealed the facts as follows ; (1) The tourmalines from the Kamihirose Formation are members of schorl-dravite solid solutions. (2) The tourmalines in the hydrothermal veins probably contain Fe3+, which substitutes for Al. (3) The metamorphic tourmalines have a wide compositional range reflecting various chemical features of host rocks.

Evolution of compositional polarity and zoning in tourmaline during prograde metamorphism of sedimentary rocks in the Swiss Central Alps

The compositional evolution of tourmaline from diagenetic to lower amphibolite-facies conditions was investigated in two metasedimentary units (redbed and black shale formations) along a traverse across the Central Alps. With increasing metamorphism, three distinct rim zones grew around detrital tourmaline cores, simultaneously with the development of prismatic neoblasts. Detrital cores and all successive rim zones are preserved in the amphibolite-facies rocks. As indicated by whole-rock data, the B required for tourmaline growth was released from illite and muscovite and was not introduced from external sources. The studied samples of tourmaline exhibit compositional polarity, i.e., their compositions are different at the opposite ends of the c axis. The compositional difference between the two poles can be expressed by the substitutions Na + Mg ;= 0 + Al and 2Al ;= Ti + Mg, with the positive pole always richer in Al and having more X-site vacancies. Both chemical and optical polar effects are most pronounced in the internal rim zones and become less prominent toward the external zones. The systematic prograde compositional trends are depicted in a vector space for Li-poor tourmaline. At low-grade conditions, the tourmaline composition is clearly controlled by the host-rock composition, but with increasing metamorphic grade the compositions of tourmaline from a variety of rocks converge. The data show that in the Central Alps, increasing metamorphic grade is reflected by increases in Ca/(Ca + Na) and Mg/(Mg + FeH), a decrease in Fe3+, and an increase in the occupancy of the X site of tourmaline.

An interpretation of boron contents within a Palaeoproterozoic volcano-sedimentary succession: Pretoria Group, Transvaal Supergroup, South Africa

Boron contents of sedimentary rocks were measured in three profiles through the Palaeoproterozoic Pretoria Group. Enhanced boron values occur at a number of stratigraphic levels across much of the preserved basin, and only these anomalies are considered significant. Evaluation of the various possible factors controlling these high boron concentrations suggests that inherited boron, sedimentation rate, detrital tourmaline, silica and carbonate dilution, metamorphism and evaporitic borates were relatively unimportant. A major role is indicated for the preferential uptake of boron by clay minerals, and for both andesitic volcanic and related hydrothermal activity as a source of boron. The dilution of boron concentrations due to organic coating of clay minerals may also be important in the case of the Pretoria Group. Stratigraphically expressed boron anomalies which cannot be explained by these various factors, are inferred to represent enhanced palaeosalinity of the waters of deposition. The suggested marine transgression is supported by sedimentological data.

Origin of hematite carrying a Late Paleozoic remagnetization in a quartz sandstone bed from the Silurian Rose Hill Formation, Virginia, USA

Paleomagnetic and petrographic studies of a quartz sandstone bed from the Silurian Rose Hill Formation of the Central Appalachians show that hematite carrying a Late Paleozoic remagnetization is authigenic. Comparison of paleopole positions from the Rose Hill Formation with Late Paleozoic poles for North America suggests a synfolding remagnetization. The sandstone cement is characterized by pore-lining hematite, pore-filling berthierine and intergrowths of hematite, berthierine and quartz. These cements postdate pressure solution of detrital quartz grains. Late Paleozoic cementation is a consequence of diagenesis associated with Alleghanian deformation. Detrital FeMg silicate grains are believed to have been a local source of Fe for some authigenic hematite and berthierine, although mass balance calculations suggest that an external source is also required. Some berthierine aggregates are pseudomorphic after detrital Fe-bearing silicate grains. Trace amounts of detrital tourmaline are the only remnants of the detrital FeMg silicates.

Tourmaline in a low grade clastic metasedimentary rock: an example of the petrogenetic potential of tourmaline

Detrital tourmaline grains and their associated tourmaline overgrowths provide a means to unravel the provenance and petrogenetic history of low grade clastic metasedimentary rocks. Evidence derives from tourmaline grains found in a lithic wacke metamorphosed to chlorite zone conditions. The detrital tourmaline cores are diagnostic indicators of the source rocks of the sediment whereas the overgrowths record both diagenetic and metamorphic reactions in the rock. Tourmaline grains consist of a detrital core surrounded by asymmetric overgrowths comprised of inner and outer rims. Abrupt chemical discontinuities between each of these zones implies that volume diffusion within tourmaline was minor under the conditions of formation. Compositions of the detrital cores vary widely, yet can be correlated with source rock types that are consistent with lithic fragments recognizable in the metawacke. At either the analogous or antilogous pole, inner rim compositions proximal to the detrital cores converge, despite the substrate tourmaline composition, indicating an approach to chemical equilibrium. However, significant dufferences in Al and X-site vacancies at the expense of Mg, Na and Ti between the analogous and antilogous poles of the inner rims demonstrate the presence of significant amounts of compositional polarity. Outer rim compositions at either pole also converge but compositional polarity between the analogous and antilogous poles persists. The presence of the inner and outer rims separated by a compositional discontinuity suggests punctuated evolution of the overgrowth. This implies that boron was sporadically available during diagenesis and metamorphism. Based on boron contents of minerals, this may correspond to a mechanism such as boron release due to polytypic change of illite or consumption of illite and/or muscovite. As such, tourmaline growth stages may serve as a monitor of chemical reactions in low grade metamorphic rocks.

The application of lithogeochemistry in the search for unconformity-type uranium deposits, Northern Saskatchewan, Canada

Lithogeochemical-mineralogical haloes around unconformity-type uranium deposits in northern Saskatchewan can expand the size of drill targets up to fifteen times. The deposits are located at or near the unconformity between Aphebian metamorphosed basement rocks in close proximity to Archean granitoids and overlying unmetamorphosed sandstones of the Helikian Athabasca Group. Deposits studied include Key Lake (Deilmann), Midwest Lake and Eagle Point. Unconformity-type deposits are associated with broad alteration haloes in the overlying sandstones and more restricted haloes in the basement rocks. The haloes in the sandstone are localized around steeply dipping fault structures and are characterized by zones of intense leaching of specular hematite and detrital heavy mineral layers and by changes in chemistry related to clay mineral alteration and tourmalinization. Clay mineral alteration haloes are common in the sandstone and basement host rocks. Interstitial clays consist mainly of kaolinite and illite with lesser amounts of chlorite. The ratio K 2O/AI 2O 3 proved useful in delineating illite-kaolinite patterns in the sandstone and in the uppermost portions of the paleoweathering profile in basement rocks. The Midwest deposit is characterized by a broad bell-shaped zone (500 m across strike) of high K 2O/AI 2O 3 ratios (>0.18) in which illite is the dominant clay mineral. The sandstone above the Deilmann deposit, on the other hand, is characterized by silicification and kaolinitization with low K 2O/AI 2O 3 ratios (<0.04). This kaolinite cap overprints a preexisting illite zone. Anomalously high boron values are characteristic of the three deposits considered in this study. Boron anomalies are similar in extent to the anomalous clay mineral alteration haloes. Altered sandstones commonly contain aggregates of radiating magnesium-rich dravite needles within the clay matrix. The interpretation of boron patterns is problema tical however, mainly because of the detrital tourmaline component in sandstones and metamorphic tourmalines present in the Aphebian metasediments. Trace elements such as U, Ni, As and Co are generally of limited use in expanding targets in sandstone because their haloes are restricted to a few tens of metres horizon-anomalies along the steeply dipping zones of mineralization related to fault structures. Uranium (>3 ppm) does form an anomaly more than 200 metres laterally across the Midwest deposit. At the Deilmano deposit anomalous uranium dispersion is restricted to within a few metres of high grade ore. In the basement rocks, the various layers of the paleoweathering profile are geochemically overprinted up to 250 m from mineralization. Bleaching related to illitization and chloritization is associated with enrichment in K 2O, MgO, B, S, U, As, Ni and P 2O 3. The ratio Fe 2O 3/MgO is useful in delineating chloritization in the upper portion of the paleo weathering profile. Deposits with large root extensions in the Aphebian metasediments such as Eagle Point, have intense dravite-chlorite-illite alteration zones which are restricted to within a few metres of mineralization across strike. ‘Quartzite” units are alteration related. The complexity of the basement lithology inhibits the use of individual elements as alteration guides other than in the intensely altered zone. The application of multivariant techniques, element ratios and clay mineralogical work prove useful in identifying the mineralogical changes at Eagle Point.

Preliminary Report of Authigenic, Euhedral Tourmaline Crystals in a Productive Gas Reservoir of the Tiger Ridge Field, North-central Montana

ABSTRACT Crystals of authigenic, euhedral tourmaline are present in a core from a productive shallow gas reservoir in the Tiger Ridge field, Montana. Overgrowths on detrital tourmaline grains have been reported by many authors, but only one report is known of discrete euhedral crystals, and these were interpreted as having a detrital origin. The tourmaline crystals discussed in this report are clearly authigenic. The tourmaline occurs as acicular or prismatic crystals, 10 to 120 microns in length, usually in intergranular pore spaces. The crystals display distinctive optical properties and typical tourmaline morphological development. Their formation appears to be controlled by access to larger pore spaces. The Upper Cretaceous Eagle Sandstone, in which the tourmaline occurs, displays abundant evidence of infrastratal alteration, and the tourmaline crystals are often associated with authigenic quartz and clays, Detrital grains of tourmaline are also present, and most display evidence of authigenic overgrowths similar to the euhedral crystals. The authigenic tourmalines probably exert several negative effects upon reservoir quality. Waters associated with Bearpaw Mountains volcanism are a likely causative agent in the formation of the authigenic crystals. This hypothesis apparently presents several constraints involving the timing of tourmalinization and gas emplacement in the Tiger Ridge field.

Authigenic Tourmaline Crystals in Pore Spaces of Upper Cretaceous Gas-Productive Sandstone, North-Central Montana: ABSTRACT

End_Page 456------------------------------Authigenic, euhedral tourmaline crystals are present in a core from a productive shallow gas reservoir in the Upper Cretaceous Eagle Sandstone of the Tiger Ridge field, north-central Montana. Detrital tourmaline is a common constituent of sands and sandstones, and although overgrowths on detrital grains have been reported elsewhere, discrete euhedral crystals of authigenic tourmaline formed in an unmetamorphosed sandstone have not been described. The tourmaline occurs as acicular or prismatic crystals of dravite which are 10 to 20 µ in length and 1 to 5 µ in diameter. The dravites usually occur in intergranular pore spaces and exhibit typical tourmaline crystal habit. An authigenic origin for these crystals is suggested by their (1) delicately euhedral morphology, (2) unabra ed appearance, (3) occurrence in growth positions, (4) similarity to dravite overgrowths within the same rock, and (5) close association with other authigenic phases. The presence of igneous rocks in the vicinity of the well, combined with the absence of tourmaline in several wells not associated with igneous rocks at Tiger Ridge field, suggests that Eocene volcanism in the Bearpaw Mountains was the source for boron, which facilitated tourmalinization. This interpretation has implications relative to the timing of gas emplacement in the Eagle Sandstone at Tiger Ridge. The gas was generated by bacteria during Late Cretaceous time; then adjacent Eocene volcanism caused tourmalinization. The gas was then remigrated into gravity-slide fault blocks in response to the Bearpaw Mountains intrusion and uplift. End_of_Article - Last_Page 457------------

Wealden detrital tourmaline: implications for northwestern Europe

Wealden detritus in S England and NW France suggests ultimate derivation from an ancient complex. This had affinities with present-day Cornubia, Armorica and NW Iberia, which apparently represent its relict flanks. Westwards, lay a Cadomian-Caledonian core. Repeated tourmalinizations occurred from pre-Cambrian times onward. These were postdeformational and may have followed separate orogenies. Geographically, the massif probably focussed on what is now the continental margin, over the Southwestern Aproaches. Structurally, it was the Cadomian-Hercynian-Galician-Caledonian convergence. Eastwards the hills diverged to encompass a lowland depression, divided into northern and southern basins by the Cornubian island. After the first sediment arrived in the ?Permian there were important fluctuations of supply and composition during the late Trias/early Jurassic, late Jurassic/early Cretaceous and Hastings Beds/Weald Clay. These may have been related to movements of the massif generated by changes in North Atlantic spreading rates and opening of Biscay.

Authigenic tourmalines from the lower Kaladgi sandstones, Jamkhandi, Mysore state

ABSTRACT The presence of different varieties of tourmaline with authigenic growths has been observed in the lower Kaladgi sandstones of Jamkhandi. Their details, origin, and significance have been discussed. The authigenesis is due to the development of minerals of complex isomorphous series of tourmaline group on any of the detrital tourmaline grains, irrespective of chemical composition. Based on the physical characters of the detrital tourmalines, the nature of the provenance has been suggested.

Mineralogy and Petrology of the Rocks Near the Quadrant-phosphoria Boundary in Southwest Montana

ABSTRACT A petrographic study was made of the rocks near the boundary of the lower Pennsylvanian Quadrant and the Permian Phosphoria formations. The mineralogy is described in detail and some of the detrital minerals, quartz, chert, tourmaline, and zircon, are subdivided into a variety of species. The chemical minerals described in detail are chert, calcite, dolomite, collophane, kaolinite, and illite. The Quadrant in this area is composed largely of fine-grained siltstones (dolomitic, illitic, and kaolinitic) and carbonate rocks. There is little significant difference in the detrital minerals of the two formations. However, the Phosphoria contains a much larger percentage of chemical rocks than the Quadrant. The detritus of the two formations was primarily derived by the reworking of older sediments. The minerals of the two formations, in this basin-edge area, comprise a quartzite-limestone series and are typical of a period of near peneplaination in the source area and belong in the shallow water marine facies of sedimentation. It is indicative of epeirogenic tectonic control both in the source area and in the locus of deposition. The rocks in the Phosphoria are modified by the deposition of an abundance of authigenic minerals and a decrease in detrital minerals. This modification was likely caused by an abundance of volcanic material in the source area.

Oolitic Limestone in the Triassic of Virginia

ABSTRACT Oolitic limestone of Manassas (Triassic) age occurs in a quarry near Culpeper, Virginia. Limestones are rare in the Virginia Triassic, and no other oolitic occurrences are known in this area. The major constituent of the rock is primary calcite; whereas illite, chlorite, and talc predominate in the insoluble residue. The heavy minerals as a group appear to be nondiagnostic as to provenance. However, the characteristics of the detrital tourmaline suggest an eastern source. The oolitic limestone apparently represents deposition in a fresh-water lake of limited areal extent. Shallow water deposition is indicated by well developed mudcracks, and minor disconformities within the bed.