Search

Apatite is an accessory phase in all the units of the internally zoned Berry-Havey complex pegmatite. This body presents a highly fractionated core zone, enriched in Li, F, B, Be, and P, which hosts three different types of pockets, some of them often containing tens to hundreds of gemmy euhedral Li-rich tourmaline crystals, together with other mineral phases such as lepidolite. Processes involved in the complex internal evolution of pegmatitic melts that give rise to zoned bodies containing pockets are not completely understood. To shed light on these processes, apatite from all the different units of the Berry-Havey pegmatite (wall zone, intermediate zone, core margin, and core zone pods) and from the three pocket types (Li-poor, Li-rich, and apatite seams) has been characterized petrographically and later analyzed for major (electronic microprobe) and trace elements (LA-ICP-MS). Results indicate that apatite chemistry changed significantly during the crystallization of the Berry-Havey pegmatite, reflecting the conditions at each stage and mainly depending on the fractionation degree, fO2, and paragenetic association. Fluorapatite is found in all the units except the core margin, the Li-poor pockets, and the seams, where Mn-bearing fluorapatite is present. A gradual increase of the Mn content in apatite from the pegmatite border (wall zone) inward, up to the formation of subrounded masses of Mn-Fe phosphate in the core zone pods, parallels the increasing fractionation of the melt. Phosphate crystallization would deplete the residual melt in Mn, probably causing the significant Mn-decrease observed in apatite from the core zone pods and Li-rich pockets. The late depletion of Mn could also be related to an increase of fO2 in the melt during the later stages of its evolution. Main trace element variations in apatite at both pegmatite and crystal scales correspond to REE, Y, and Sr. Yttrium and REE behave in a very similar way, decreasing inward, i.e., with fractionation of the pegmatitic melt (ΣREE from 1796 ppm in the apatite from the wall zone to 0 ppm in the core zone; and Y from 1503 ppm in the apatite from the wall zone to 0 ppm in the core zone); which could be due to early crystallization of REE-bearing phosphates such as monazite and xenotime. Strontium shows a more complex trend, with an initial depletion in apatite from the wall zone (52 ppm) to the intermediate zone (3 ppm) and a pronounced increase from the core margin (23–87 ppm) up to the core zone and pockets (up to 2.87 wt%). This increase of Sr at the latest fractionation stages of the pegmatite is interpreted to be associated with a late, incompatible character of this element in highly fractionated melts, related to the composition of feldspars from the core margin (mainly pure albite). The lack of Ca in feldspars would decrease affinity for Sr incorporation into their structure and, consequently, Sr would go preferentially to apatite in the core zone pods and, more markedly, in the pockets. Apatite also records changes in the redox conditions during crystallization, with the highest fO2 at the end of the crystallization, mainly reflected in the Eu and Ce anomalies. The chemistry of apatite also reflects the evolution of the pegmatitic melt during crystallization regarding the fluids saturation and pockets generation. Accordingly, at least two exsolution events took place during the Berry-Havey crystallization history: (1) at the beginning of the core zone crystallization, giving rise to the Li-poor pockets, and (2) after the crystallization of the Li-rich pods of the core zone, resulting in the Li-rich pockets. The apatite-rich seams may have crystallized between these two exsolution events or later, at a subsolidus stage, after a Na-autometasomatism episode. This study shows how a detailed petrographic and chemical characterization of apatite associated with different units of a highly fractionated, internally zoned pegmatite may help understand the crystallization history of pegmatitic melts. It is also evidenced that during the internal evolution of pegmatites, apatite chemistry records variations in the fO2, elemental fractionation, interaction with competing mineral phases, fluids activity and exsolution events. In addition, it is shown how apatite chemistry may be useful as an exploration tool for pegmatites. [ABSTRACT FROM AUTHOR]

This paper addresses the study of a pillow lava interbedded with Late Albian-Early Cenomanian sediments that crops out in Armintza (Bizkaia, Northern Spain). The lava flow is an alkaline basalt with abundant macrocrysts of clinopyroxene, kaersutite, Ca-rich plagioclase (50-86% An) and ilmenite, which display a variety of textures and complex zoning patterns indicative of open-system magmatic behaviour. Macrocryst cores are likely to be inherited antecrysts that underwent complex processes under deep pre-eruptive conditions (≈ 700-800 MPa). Microcrysts and macrocryst rims formed during magmatic ascent and emplacement at shallower levels (≈ 35 MPa). Hypothetical melts in equilibrium with clinopyroxenes and amphiboles have trace element compositions like metasomatic vein melts containing amphibole, and their patterns overlap with those of the Armintza pillow lava. This suggests a metasomatised lithospheric mantle with amphibole-rich veins as a potential source for the alkaline basaltic melt. It is even conceivable that the Armintza pillow lava and other alkaline volcanic manifestations of the Basque-Cantabrian Basin were part of the same magma plumbing system through which a series of time-limited eruptions of different batches of magma ascended from the lithospheric mantle to the upper crust during the Albian to the Santonian. [ABSTRACT FROM AUTHOR]

A new type of Li mineralisation in hard rock has been found to occur in the Valdeflórez area (Cáceres, Spain), where there is 111.3 Mt of resources and a mean value of 0.61 wt% of Li2O. Lithium is mainly held by very fine-grained micas, important constituents of Ordovician psammopelitic rocks belonging to the Palaeozoic metasedimentary sequence of the Cáceres syncline. The mineralised zone has an elliptical surface shape with a dimension of ~ 700 × 500 m. Lithium-bearing rocks show a characteristic layered appearance, in which light grey quartz-micaceous laminae < 1 mm to some centimetres in thickness, with a variable ratio of quartz to mica, alternate with fine to very fine-grained, dark grey to black tourmalinite laminae parallel to the regional foliation. Subvertical quartz + (montebrasite)-veins that cut the regional foliation at an extremely high angle are also common in this area. Mineralisation and the associated veins are likely to be linked to the intrusion of the nearby Cabeza de Araya pluton. The infiltration of granite-derived Li-, F-, B- and P-rich aqueous fluids into the host rocks through fractures related to shearing processes is considered to be the cause of the formation of Li-rich micas and intense tourmalinisation at the expense of pre-existing phyllosilicates. [ABSTRACT FROM AUTHOR]

Tourmaline occurs in peraluminous granites from the Central Iberian Zone associated with two main AFM mineral assemblages: (1) muscovite + biotite ± cordierite ± andalusite in the Araya-type granites; (2) muscovite ± biotite ± garnet in leucogranites from the Alamo complex. When tourmaline is dominant, biotite is an accessory or absent, and vice versa. We present field and petrographic relations, mineral chemistry, and geochemical data for tourmaline-bearing and tourmaline-free granitic rocks from various localities in the Central Iberian Zone. Compositional phase diagrams are used to evaluate the factors controlling the occurrence of tourmaline relative to biotite in granitic rocks, with particular emphasis on the relationships between mineral assemblage and whole-rock chemistry and its petrological implications. Although tourmaline stability in felsic magmas depends on the interplay between rates of changing environmental conditions such as bulk composition, T, aH2O, and fO2, the principal factor dictating tourmaline formation is the B content of the melt, judging from phase relations. In short, regardless of other variables, granitic melts have to surpass a critical boron threshold to achieve tourmaline saturation. Experimental constraints, combined with petrographic and geochemical data, suggest minimum boron contents in the range of ∼500–3000 µg g–1 (depending on temperature) to saturate melt in tourmaline. Acting in concert with boron content, other variables such as Al2O3 , mafic components, T, fO2, and so on, control not only the formation of tourmaline during melt crystallization, but also the magnitude of boron loss from the magma to the surrounding rocks. The analysis of phase relations suggests that tourmaline granites usually form units distinct from biotite granites because common granitic melts have restricted accessibility to the three-phase Tur–Bt–Ms field. [ABSTRACT FROM AUTHOR]

The Alamo Complex consists of structural-metamorphic domes surrounded by low-grade metasedimentary rocks of Upper Proterozoic to Lower Cambrian age that form part of the Schist Graywacke Complex (Central Iberian Zone, Spain). Tourmaline is ubiquitous throughout the domes, in which it occurs in tourmalinites, psammo-pelitic schists, quartzites, gneisses, migmatites, leucogranites, aplo-pegmatites, and quartz veins. Overall, tourmaline compositions can be described within the four component system schorl-dravite-foitite-magnesiofoitite, with K2O < 0.23%, low Ca contents, Mg/(Mg+Fe) = 0.25-0.71 and X/(X+Na) = 0.18-0.43, where X = vacancies in the X site. Field relations and petrographic observations, combined with tourmaline 40Ar/39Ar data, provide evidence of intense boron metasomatism affecting this region. Tourmaline 40Ar/39Ar step-heating spectra for Cambrian-Ordovician orthogneisses are complex, yielding a pseudo-plateau age of ~370 Ma that is interpreted to reflect Variscan rejuvenation of older tourmaline. Tourmaline 40Ar/39Ar data for mylonitized and folded tourmalinites yield disturbed spectra with pseudo-plateau ages of ~355-342 Ma that are unsuitable for precise age determination. These ages, however, are consistent with published ages (340-350 Ma) for the second Variscan deformation (D2). Tourmaline from fine-layered tourmalinite and metasedimentary rocks yield well-defined plateau ages of 317 and 315 Ma, respectively, recording an additional metasomatic event concomitant with anatexis and evolution of B-bearing granites, pegmatites, and hydrothermal fluids. The different tourmaline-forming stages reflect significant boron cycling within the continental crust of the Central Iberian Zone, driven by deformation, metamorphism, and magmatism during the Variscan orogeny. Boron-rich aqueous fluids related to Cambro-Ordovician magmatism are considered to be the primary source of boron. [ABSTRACT FROM AUTHOR]

The Li-F-Be-B-P bearing Pinilla de Fermoselle (PF) pegmatite occurs in the apical part of a leucogranite body. It shows a clear non-symmetrical vertical zoning from the contact with the leucogranite to a contact with the metamorphic country rocks, The pegmatitic facies evolve upward from (1) the undifferentiated Lower Border Zone (LBZ), with quartz, feldspars, muscovite, biotite, and black tourmaline, through (2) the Intermediate Zone (IZ), with quartz, muscovite, zinnwaldite, black tourmaline, and Fe-Mn phosphates, to (3) the highly evolved Upper Border Zone (UBZ), with quartz, albite, lepidolite, zinnwaldite, elbaite, and beryl. The composition of the pegmatite-forming minerals suggests that a residual melt become progressively enriched in F and Li until the crystallization of the apical UBZ, whereas P partitions in the melt only until the intermediate levels of differentiation attained in the IZ. Chemical variations in the mica and tourmaline as well as in the feldspar and Fe-Mn phosphate minerals are consistent with an internal evolution by crystal fractionation processes. A plausible model for the crystallization of the PF pegmatite involves a rapid, in situ, bottom-up crystallization from significantly undercooled liquids. The lack of metasomatic effects in the metamorphic host-rock and the estimated P content of the initial leucogranite melt suggest that the PF pegmatite mainly crystallized under closed system conditions. [ABSTRACT FROM AUTHOR]

The Cañada pegmatite (Salamanca, Spain), a Li-P-(Sn-Nb ± Ta)-bearing granitic pegmatite, is intruded partly into a gabbro and partly into a leucogranite. Three phosphate associations have been distinguished, based on paragenesis, texture, and chemistry: (1) ferrisicklerite-magniotriplite-john-somervilleite association (in the border zone), in which Mg-bearing phosphates and coexisting Fe-Mg silicates are abundant; (2) ferrisicklerite-graftonite association (in the transition zone) characterized by higher values of Fe/(Fe + Mg) than in the border zone; and (3) triphylite-sarcopside association (in an inner zone), which also includes minor montebrasite, ferrocolumbite, and cassiterite, typical of an evolved pegmatite facies. As a result of the decrease of Mg, the Fe/(Fe + Mg) ratios for phosphates, biotite, and tourmaline increase from the border to the inner association (e.g., for ferrisicklerite and graftonite, from 0.67 and 0.85 in the border to 0.94 and 0.98 in the inner association, respectively). This difference is particularly evident for biotite and tourmaline; for example, the Fe/(Fe + Mg) ratios for tourmaline range from 0.59 in the border to 0.86 in the inner zone. These variations seem to reflect contamination of marginal zones of the pegmatite by some type of reaction with the host gabbro. Thus, an evolutionary trend involving inward crystallization from the margins and contamination of fluids from wallrocks into pegmatite-forming melt may be a plausible genetic model. The occurrence of phosphates along with Fe-Mg silicates would indicate that the melt contained on the order of 1.3-2.4 wt% P[sub2]O[sub5], based on experimental silicate-phosphate equilibria. [ABSTRACT FROM AUTHOR]

Presents a study on the mineralogy, geochemistry and geological significance of tourmaline-rich rocks from western Pyrenees, Spain. Names of the three types of tourmaline-rich rocks; Geological setting of the rocks; Detailed information on the distribution and occurence of tourmaline-rich rocks.

Provides information on a study on the mineral paragenesis and chemistry of tourmaline and associated micas from the Valdeflores area in Caceres, Spain. Three litholic assemblages that can be distinguished in the area; Methodology; Information on tourmaline and micas; Chemistry of tourmaline and micas; Discussion and conclusions.

In this paper we report a combined zircon U–Pb–O isotopes and bulk-rock Sr–Nd–O isotopes study on granitic rocks from the Jálama pluton, Central Iberian Zone. Zircon U--Pb ages of representative granitic rock samples are bracketed in the range of 306–304 ± 3 Ma, but within the level 2σ errors of U--Pb ages. Therefore it is not possible to establish differences in intrusion ages between the main granitic units that make up the Jálama pluton. Microgranular enclaves appear to be slightly older (309 ± 2 Ma), but they do overlap with the age of the granitic rocks. Sr--Nd isotopic data for enclaves of tonalitic composition preclude a simple mantle or crustal origin, but high mean zircon δ 18O values of 8.65 ± 0.9‰ and δ18O(WR) values of 9.96–10.56‰ reflect a largely crustally contaminated magma. The combination of field relations, petrography, bulk-rock geochemistry, Sr-Nd-O isotopic data, zircon δ18O values and U--Pb ages provide compelling evidence that the granites from the Jálama pluton: (i) were coevally formed involving assimilation and mingling/mixing concomitant to fractional crystallization; and (ii) represent typical S-type granites that evolved from a same crustal source, potentially metasedimentary rocks from the Schist Greywacke Complex by considering the Neoproterozoic ages of the inherited zircons. [Display omitted] • The Jálama pluton is a Variscan peraluminous granitoid from the Central Iberian Zone. • It includes three units with minor microgranular and metasedimentary enclaves. • Zircon U--Pb ages of granitic rocks are in the range of 309–304 Ma. • The δ18O(Zr) values for the granites indicate a crustal source. • Bulk-rock (Sr-Nd-O) isotopic data are consistent with a crustal origin. [ABSTRACT FROM AUTHOR]

Primary Fe Mn phosphates from four pegmatites (Cañada, Palermo#1, Palermo#2 and Palermo#11) typical of the beryl-columbite-phosphate subtype have been characterized texturally and geochemically. Most of the common Fe Mn phosphates (triphylite, sarcopside, ferrisicklerite, wagnerite and wolfeite) are extremely poor in trace elements, with the exception of Zn for all them, Li for sarcopside, and Nb and Ta for wagnerite and wolfeite. Calcium-bearing Fe Mn phosphates (graftonite and johnsomervilleite) are the richest in trace elements, with contents usually over the mean continental crust for Zn, Y, REE and Pb. Crystal-chemical constraints, combined with paragenetic relationships, geochemical and geological processes, are thought to control the content, distribution and behavior of trace elements in Fe Mn phosphates. Zinc contents in graftonite and triphylite increase with fractionation, whereas Y, Nb, Ba, REE, U and Pb contents in graftonite decrease. Crystallization of REE-bearing phases, such as xenotime-(Y), strongly affects the REE content of the Fe Mn phosphates. Recrystallization processes also seem to affect the trace element contents in phosphates. The earliest primary phosphate associations from Cañada and Palermo pegmatites (those containing graftonite), show Y/Ho and Zr/Hf ratios inside or close to the CHARAC (Charge-and-Radius-Controlled) field. This could indicate that such associations crystallized in a magmatic stage without a high H 2 O activity. Phosphates from the latest associations plot outside the CHARAC field, suggesting that fluid activity became important during the crystallization of these latest associations. Ti-in-biotite, garnet-biotite and triphylite-sarcopside geothermometers have yielded relatively high temperatures of crystallization, between 633 and 386 °C, for the earliest associations (presumably crystallized under magmatic conditions). In contrast, the latest associations, whose crystallization presumably proceeded with a higher H 2 O activity, are in the range of 281–360 °C. • Primary Fe Mn phosphates are common minerals in some pegmatite types. • Only preliminary data are published on the trace element contents in these phases. • There is a strong structural control on trace elements contents in these phosphates. • Trace elements distribution in phosphates also depends on geochemical factors. • Chemistry of phosphates records the crystallization history of pegmatitc melts. [ABSTRACT FROM AUTHOR]

• A copper mineralization with chrysocolla, malchite and azurite has been studied. • The mineralization is related to a red-bed sequence with a stratabound morphology. • Formation of copper ores occurs under oxidizing conditions. • Isotopic studies suggest climatic variations conditions and meteoric solutions. • Cu-bearing veins from the Hercynian basement are likely the source of copper. • The Navas de San Juan mineralization is a typical exotic copper deposit. The Navas de San Juan copper deposit is located at the southeast edge of the Iberian massif (Spain). It occurs within Triassic continental red beds that represent an undeformed, horizontal to sub-horizontal sequence, overlying unconformably folded Paleozoic metasedimentary rocks and, locally, granitic rocks. The red beds consist essentially of siliciclastic detrital materials including sandstone, silt, and clay, with some thin layers of micritic limestones and edaphic carbonates. This sequence was formed in a sedimentary framework typical of a low sinuosity fluvial system of braided type. The copper mineralization is hosted by a fine-grained sandstone (arkose) with abundant plant debris and detrital grains cemented by dolomite, which was deposited in a secondary fluvial channel. The copper mineralization includes chrysocolla, azurite and malachite with a stratabound morphology. Chrysocolla occurs unevenly in the sandy levels of the mineralized horizon replacing feldspar grains, coating detrital grains and dolomitic cement, and filling pores and cavities. Copper carbonates appear essentially inside or near the organic matter-rich zones filling cavities and veinlets. They also replace more or less limonitized plant debris preserving the original cellular structure of organic material. Azurite and malachite occur in different layers or zones without any evidence of reaction between them. The δ13C-values of azurite and malachite are indicative of a carbon source derived from the decomposition of C 3 plant debris. The δ 18O values of the solutions in equilibrium with copper carbonates are consistent with solutions of meteoric origin. The differences between the values for azurite and malachite would reflect variations of the climatic conditions, probably related to seasonal changes in the hydrological parameters and arid degree of the system. Chrysocolla formation was due to the neutralization of copper solutions during the hydrolysis and replacement of the feldspars, with additional precipitation of chrysocolla in interstitial spaces, cavities and microfractures. Copper carbonates derived from the interaction between the neutralized copper solutions and the CO 2 released by the decomposition of organic matter under oxidizing conditions. Based on geological, mineralogical and petrographic criteria, in conjunction with isotopic data, the Navas de San Juan deposit is interpreted to represent an exotic copper mineralization. The Cu-bearing vein mineralizations located in the Variscan basement are inferred as the possible copper source. [ABSTRACT FROM AUTHOR]

The Berry-Havey pegmatite (Oxford pegmatite field, Androscoggin County, Maine, U.S.A.), enriched in Li, F, B, Be, and P, is intruded in hornblende-rich amphibolite, with minor biotite or diopside. The pegmatite has a complex internal structure, with four texturally and compositionally different zones that show an increasing degree of evolution inward: wall zone, intermediate zone, core margin, and core zone. The main minerals are quartz, feldspars, Al-micas, tourmaline, with minor Fe-micas, garnet, beryl, amblygonite-montebrasite, Fe-Mn phosphates, and apatite. Tourmaline is present in all zones of the pegmatite, showing different textures: black anhedral crystals in the wall and intermediate zones; black prisms of up to 40 cm in length in the intermediate zone; black tapered prisms, surrounded by a pseudo-graphic intergrowth of quartz or albite with black ± green/bluish tourmaline, and constituting a continuous layer under the core zone; multicolored and "watermelon" zoned crystals in the core zone; and gemmy deep green and color-zoned "watermelon" tourmaline prisms, up to 15 cm length, inside the pockets. A complete chemical evolution from Mg-rich schorl in the wall zone to elbaite with an important deprotonation in the pockets inside the core zone is observed. The most plausible exchange vectors for this chemical evolution are FeMg-1, YAlWO[YR2+W(OH)]-1 and Al[X]X(R2+Na)-1 (where R2+ = Fe2++Mg2++Mn2++Zn2+), for the tourmalines from the wall and intermediate zones. In the core margin, tourmaline composition evolves from schorl toward Li-rich species through the substitution (YAlYLiYR-22+). Later, during the crystallization of the core zone, this exchange vector combined with the substitution ([X] YAl0.5XNa-1YLi-0.5). Finally, the gemmy tourmalines from the pockets show a deprotonation related to the exchange vector YAlWO2YLi-1W(OH)-2 and may be classified as darrellhenryite. These substitutions may reflect an increase in oxygen fugacity and a decrease in Li and F related to the crystallization of lepidolite and amblygonite-montebrasite in the core zone adjacent to or within the pockets. The crystallization of these minerals would reduce the availability of Li and F for the very latest tourmaline crystals, growing inside the pockets, where the deprotonation becomes important. Chemical and textural variation in tourmaline is consistent with a fractional crystallization process for the internal evolution of the Berry-Havey pegmatite. Crystallization of the tourmaline layer under the core zone may be related to the exsolution of the fluid phase implied in the formation of pockets. [ABSTRACT FROM AUTHOR]

Field, textural, paragenetic, and chemical data for micas from pegmatites of the Fregeneda-Almendra pegmatitic field (Central-Iberian Zone) are used to characterize and evaluate their petrogenesis. These pegmatites show a zonal distribution from barren to evolved, with an increase in degree of evolution with increasing distance from the Mêda-Penedono-Lumbrales leucogranite. Five types of evolved pegmatites have been recognized: (1) petalite-rich, (2) spodumene-rich, (3) Li-mica + spodumene-rich, (4) Li-mica-rich, and (5) cassiterite-rich pegmatites, plus six types of barren and intermediate pegmatites. Representative micas from the different pegmatite types and from the leucogranite were analyzed for major and trace elements. All micas belong to the muscovite-lepidolite series. Lithium is incorporated into Li-micas via the Li3Al-1〉-2 and Si2LiAl-3 substitutions, where 〉 represents vacancies. The Al4Si-3〉-1 and Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. substitutions, where R2+ = (Fe + Mg + Mn), account for the compositional variability of micas from the Li-mica-free pegmatites. The Li, Rb, Cs, Be, Ta, and Nb contents of micas increase in the order: leucogranites and barren pegmatites < intermediate pegmatites < spodumene-bearing and petalite-bearing dikes < Li-mica-bearing pegmatites. The Ba content decreases in the same order, and Sn and Zn are relatively abundant in the intermediate pegmatites. These variations are consistent with rare-element enrichment via fractionation processes combined with partitioning of rare elements from the pegmatite melt into the minerals and volatile phases. However, some pegmatite types occurring in this area, such as the cassiterite-rich dikes, do not seem to form part of the same evolutionary trend. [ABSTRACT FROM AUTHOR]

Granitic pegmatites are widespread within a schist-metagreywacke complex in the Fregeneda-Almendra area (Central Iberian Zone). They intrude pre-Ordovician metasedimentary rocks and show a zonal distribution relative to the Meda-Penedono-Lumbrales granitic complex, from barren bodies to those enriched in Li, F, Sn, Nb>Ta, P and Be. Based on mineralogical criteria, these pegmatites are classified into three main categories: barren, intermediate and rare-element pegmatites, with each type including various subtypes. Phosphates are present in many pegmatites that usually occur as fine-grained accessory minerals. The most complex association of such minerals includes numerous Fe–Mn phosphates that occur in intermediate pegmatites. Al-phosphates are characteristic of Li-rich pegmatites. Electron microprobe analyses of representative phosphates reflect compositional differences depending on the pegmatite type. The Fe/(Fe+Mn) ratio of phosphates tends to decrease as the evolution degree of the pegmatites increases. [ABSTRACT FROM AUTHOR]

Based on field and petrographic observations, mineralogical, geochemical (whole-rock by ICP-MS, ICP-OES, ISE and PGNAA) and geochronological (Ar Ar on mica and U Pb on columbite) data, ten pegmatite types and one type of cassiterite-rich quartz hydrothermal veins have been distinguished in the Fregeneda-Almendra field (FA) (Central Iberian Zone), some of them highly enriched in Li (included in petalite, spodumene and Li-rich mica). The pegmatites and the veins mostly intrude Neoproterozoic to Cambrian rocks from the Schist-Greywacke Complex. Felsic igneous magmatism during syn - to late-D 3 stages (≈ 320–295 Ma) of the Variscan orogeny was important and nearly continuous in the area, with the overlap of different granitic units of highly peraluminous S-type composition. The most important in outcrop corresponds to the Mêda-Escalhão-Penedono-Lumbrales granitic complex (MEPL), which belongs to a two-mica leucogranitic series. The other granitic units (Saucelle, Feli and East-MEPL granites) are younger and belong to a P-rich, Ca-poor monzogranitic series. Spatial relationships, together with chemical, mineralogical and geochronological data, indicate that all the pegmatite types and the cassiterite-rich quartz hydrothermal veins are not cogenetic, being related to three different magmatic events: (i) (≈ 319–313 Ma) includes the syn -D 3 MEPL granite and three types of barren pegmatites (intragranitic, quartz+andalusite layers and simple concordant pegmatites); (ii) (≈ 305–300 Ma) corresponds to the late to post-D 3 Feli granite, related to a group of cassiterite-rich quartz veins; and, (iii) (≈ 300–298 Ma) represents the late- to post-D 3 East-MEPL and Saucelle granites, likely parental of some barren aplitic-pegmatitic apophyses and the discordant intermediate and Li-rich pegmatites. These latter form part of a general granite-pegmatite fractionation trend. • Different pegmatite generations coexist in the FA field and one of them is Li-rich. • A petrogenetic model based on geochemical and geochronological data is made for them. • The FA Li-rich aplite-pegmatites have a magmatic affiliation. • They formed by extreme fractionation of P-rich, Ca-poor peraluminous granitic melts. • This model may be applied to other Variscan Li-rich aplite-pegmatites from Europe. [ABSTRACT FROM AUTHOR]

Abundant Li-Cs-Ta aplite-pegmatite dykes were emplaced in the western Central Iberian Zone of the Iberian Massif during the Variscan Orogeny. Their origin and petrogenetic relationships with the widespread granitoids have led to a currently rekindled discussion about anatectic vs. granitic origin for the pegmatitic melts. To deal with these issues, the aplite-pegmatite dykes from the Tres Arroyos area, which constitute a zoned pegmatitic field related to the Nisa-Alburquerque granitic batholith, have been studied. This work comprises a complete study of Nb-Ta-Sn oxides' mineralogy, whole-rock geochemistry, and U-Pb geochronology of the aplite-pegmatites that have been grouped as barren, intermediate, and Li-rich. The most abundant Nb-Ta-Sn oxides from Tres Arroyos correspond to columbite-(Fe), columbite-(Mn) and cassiterite. Niobium-Ta oxides show a marked increase in the Mn/(Mn+Fe) ratio from the barren aplite-pegmatites up to the Li-rich bodies, whereas variations in the Ta/(Ta+Nb) ratio are not continuous. The probable factors controlling fractionation of Mn/Fe and Ta/Nb reflected in Nb-Ta oxides may be attributed to the crystallization of tourmaline, phosphates and micas. The lack of a progressive Ta/Nb increase with the fractionation may be also influenced by the high F and P availability in the parental pegmatitic melts. Most of the primary Nb-Ta oxides would have crystallized by punctual chemical variations in the boundary layer, whereas cassiterite formation would be related to an undercooling of the system. Whole-rock composition of the distinguished lithotypes reflects similar tendencies to those observed in mineral chemistry, supporting a single path of fractional crystallization from the parental Nisa-Alburquerque monzogranite up to the most evolved Li-rich aplite-pegmatites. The age of 305 ± 9 Ma, determined by LA-ICP-MS U-Pb dating of columbite-tantalite oxides, reinforces the linkage of the studied aplite-pegmatites and the cited parental monzogranite. [ABSTRACT FROM AUTHOR]