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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]

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 [K.sub.2]O < 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 [sup.40]Ar/[sup.39]Ar data, provide evidence of intense boron metasomatism affecting this region. Tourmaline [sup.40]Ar/[sup.39]Ar 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 [sup.40]Ar/[sup.39]Ar 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 ([D.sub.2]). 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. Keywords: Tourmaline, petrography, chemical composition, [sup.39]Ar/[sup.40]Ar dating, Alamo Complex, Central Iberian Zone, Spain

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.

The Canada pegmatite (Salamanca, Spain), a Li-P-(Sn-Nb [+ or -] 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.sub.2][O.sub.5], based on experimental silicate-phosphate equilibria.

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]

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]