Obsidian was a key toolstone for the development of maritime lifeways in the western archipelago of southernmost South America. This area is a fragmented landscape where the major north–south movement of people along the Pacific was only possible by navigation because it is constrained by major biogeographic barriers. Two obsidian sources have been recorded, each one located on the extremes of the archipelago, and each has played a key role in the canoe-adapted societies that used them. As indicated by repeated inductively coupled plasma mass spectrometry analyses, obsidian from Chaitén Volcano to the north was distributed between 38°26′ S and 45°20′ S, and obsidian from Seno Otway to the south was distributed between 50° and 55° S, although it mainly occurred in sites close to the Strait of Magellan and within constrained time periods. This study explores the distribution of these two types of obsidians, their chronology, their frequencies in the archaeological record, the main artifact classes that are represented, and the technological processes in which they were involved. This examination indicates common aspects in the selection of high-quality toolstones for highly mobile maritime groups and discusses the different historical trajectories of two obsidians that appear decoupled across the Holocene.

The Salado and Verde streams constitute the two main seasonally available freshwater courses that flow into the Atlantic coast of the Rio Negro province (continental Patagonia, Argentina, 42 degrees South). This would have favored their use in the past as corridors for human circulation between the coast and the interior. This paper presents the results of the technomorphological and geochemical analyses of the obsidian artifacts recovered in the area to constrain mobility. The results allow us to propose the existence of toolkit reconditioning or replacement activities, and the identification of different sources of provenance of the obsidians (Sacanana, Telsen, and Portada Covunco, distant up to 800 km from the study area), reinforcing the hypothesis of a coast-inland circulation, with the possible existence of circuits of exchange of this raw material.

Two magmatic REE-rich occurrences, located near Jamestown, Colorado, and hosted in the Precambrian Longs Peak granite batholith, exhibit unusual textures that suggest formation by fluoride-silicate melt immiscibility. Both contain small (<2 mm diameter) globular F-, P-, and REE-rich segregations of fluorite and monazite-(Ce). In addition, the northern of the two localities preserves evidence of a second melt immiscibility event in the form of larger (up to several cm diameter) aplite-hosted globular segregations of fluorite and the REE minerals allanite-(Ce), monazite-(Ce), fluorbritholite-(Ce), törnebohmite-(Ce), and cerite-(Ce). The southern of the two localities lacks these cm-scale globular textures, but instead contains much larger aggregates of these same REE minerals, with up to >57 wt.

We report a previously unknown black obsidian outcrop located at the eastern end of the Deseado Massif, near the Atlantic Ocean and the town of Tres Cerros, in Patagonia. This obsidian is a subalkaline rhyolite glass with medium potassium content. It is of lower quality than the black obsidian from the Pampa del Asador source, located in the vicinity of the headwaters of the Chico River, in the northwest of Santa Cruz. The ICP-MS and INAA geochemical data obtained for 16 obsidian samples are comparable when measurement uncertainties are considered. However, these are significantly different from published ICP-MS data for samples from Pampa del Asador and 17 de Marzo, indicating that obsidian from Tres Cerros can be differentiated geochemically from these secondary sources. A black obsidian artifact from the Alero 4 site, located on the northeastern coast of Santa Cruz, was analyzed, showing macroscopic characteristics similar to those identified in the Tres Cerros samples. The results indicated that it was an obsidian from Pampa del Asador. Likewise, the geochemical trends obtained for the Tres Cerros samples were not compatible with those observed in artifacts from the Alero del Valle and Cueva Aristizabal sites, located close to the southeast coast of Santa Cruz. In this sense, we emphasize that no evidence has yet been recorded that indicates the exploitation of Tres Cerros source by human hunter-gatherer groups that occupied the Patagonian region in the past. In this framework, the geochemical characterization of the potential source presented here constitutes initial information which can be compared with the one obtained from artifacts in archaeological sites, providing information to understand human mobility and the criteria for raw material selection.

El sitio Campo del Lago 4 se ubica en los campos de invernada de la estancia Bon Accord en la costa sur del lago Argentino (cuenca superior del río Santa Cruz). Sobre la base de una muy alta frecuencia de artefactos de obsidiana gris verdosa veteada (OGVV) y de artefactos formatizados confeccionados sobre otras materias primas líticas también de muy buena y excelente calidad para la talla se presentan las particularidades de este sitio en el contexto de la margen sur del lago Argentino y se evalúan las condiciones de obtención de la OGVV. Se discute su circulación a escala suprarregional comparada con la de otras dos obsidianas, la verde y la negra, también presentes en el sitio, pero en una frecuencia mucho menor. La circulación de la OGVV muestra una curva de distribución bimodal cuyos extremos corresponden a la margen sur del lago Argentino y al Campo volcánico Pali-Aike. En el primer caso, la proximidad a la fuente de origen habría resultado en el acceso directo, oportunista y poco usual; mientras que, en el segundo, el aprovisionamiento habría sido indirecto y se obtuvo por circulación de lascas y/o nódulos. Sobre la base de la representación artefactual regional, la fuente de la OGVV estaba espacialmente restringida o -más aún- sería muy puntual. La OGVV solo fue otra roca más de excelente calidad dentro de la panoplia de aquellas disponibles para la talla. Los sistemas cazadores recolectores -tanto en una escala regional como suprarregional- no la ignoraron cuando las circunstancias se daban, pero no la habrían requerido en demasía.

The Campo del Lago 4 site is located in the wintering grounds of the Bon Accord ranch on the Southern shore of Lake Argentino (upper basin of the Santa Cruz River). Based on a very high frequency of veined greenish-gray obsidian (OGVV) artifacts and tools made from this and other lithic raw materials also of very good and excellent quality for knapping, the particularities of this site are presented in the context of the South bank of Lake Argentino and the conditions for obtaining the OGVV are evaluated. Its circulation on a supraregional scale is discussed compared to two other obsidians, green and black, also present at the site but at a much lower frequency. The circulation of the OGVV shows a bimodal distribution curve whose extremes correspond to the Southern margin of Lake Argentino and the Pali-Aike volcanic field. In the first case, proximity to the source of origin would have resulted in direct, opportunistic and unusual access, while in Pali-Aike volcanic field, the supply would have been indirect and was obtained by circulation of flakes and/or nodules. Based on the regional artifactual representation, the source of the OGVV was either spatially constrained or, moreover, very focal. The OGVV was just another excellent quality rock in the panoply of those available for knapping; hunter-gatherer systems-both on a regional and supra-regional scale-did not ignore it when the circumstances arose, but they would not have required it too much.

AbstractRounded to angular granoblastic textured mafic xenoliths, ranging from ∼1 to 6 cm in dimension, occur together with mantle peridotite xenoliths in a small Neogene/Quaternary alkali basalt cone in northeastern Iran. These crustal xenoliths consist of plagioclase feldspar, clinopyroxene, orthopyroxene and minor olivine, spinel, titanomagnetite and apatite. Their bulk compositions are similar to tholeiitic basalts and they are interpreted as meta-gabbroic rocks derived from mid- to lower crustal depths of 18 to 30 km. Rb–Sr dating suggests an age of c. 457 ± 95 Ma for these crustal xenoliths, and their geochemistry shows some similarities to Ordovician gabbros that crop out ∼20 km to the west. The data suggest that the gabbroic proto-lithologies of the xenoliths formed by intrusion of mafic magmas into the mid- to lower crust, possibly during extension and magmatism related to the opening of the Hercynian Palaeotethys ocean that separated central and eastern Iran from the Eurasian plate during the Late Palaeozoic.

Se informa sobre la presencia de un afloramiento de obsidiana negra previamente desconocido ubicado en el extremo oriental del Macizo del Deseado, en cercanías del Océano Atlántico y de la localidad de Tres Cerros, en Patagonia. La obsidiana constituye un vidrio de riolita subalcalina con contenido medio de potasio. Es de menor calidad que la obsidiana negra de la fuente Pampa del Asador, emplazada en inmediaciones de la cabecera del río Chico, en el noroeste de Santa Cruz. Los datos geoquímicos de ICP-MS e INAA, obtenidos para dieciséis muestras de obsidiana son comparables cuando se consideran las incertidumbres de medición. Sin embargo, estos son significativamente diferentes a los datos de ICP-MS publicados para muestras procedentes de Pampa del Asador y 17 de Marzo, lo que indica que la obsidiana de Tres Cerros se puede diferenciar geoquímicamente de las mencionadas fuentes secundarias. Se analizó un artefacto de obsidiana negra procedente del sitio Alero 4, ubicado en la costa noreste de Santa Cruz, que presentaba características macroscópicas similares a las identificadas en las muestras de Tres Cerros. Los resultados indicaron que se trataba de una obsidiana procedente de Pampa del Asador. Asimismo, las tendencias geoquímicas obtenidas para las muestras de Tres Cerros no resultaron compatibles con las observadas en artefactos de los sitios Alero del Valle y Cueva Aristizábal, emplazados próximos a la costa sudeste de Santa Cruz. En este sentido, si bien aún no se han registrado evidencias que indiquen la explotación de la fuente Tres Cerros por parte de grupos humanos cazadores-recolectores que ocuparon Patagonia en el pasado, la caracterización geoquímica de la fuente Tres Cerros aquí presentada constituye información que podrá ser comparada con muestras procedentes de sitios arqueológicos ubicados a distintas distancias de ella, contribuyendo de esta manera a entender la movilidad humana en la región, así como los criterios de selección de materias primas.

Cryptotephra deposits (microscopic volcanic ash) are important geochronological tools that can be used to synchronize records of past environmental change. Here we report a distal cryptotephra from a Holocene peat sequence (Canopus Hill) in the Falkland Islands, in the South Atlantic. Using geochemical analysis (major- and trace-element) of individual volcanic glass shards, we provide a robust correlation between this cryptotephra and the large mid-Holocene explosive eruption of Mt. Hudson in Patagonia, Chile (H2; similar to 3.9 ka cal BP). The occurrence of H2 as a cryptotephra in the Falkland Islands significantly increases the known distribution of this marker horizon to more than 1200 km from the volcano, a threefold increase of its previous known extent. A high-resolution radiocarbon chronology, based on terrestrial plant macrofossils, dates the H2 tephra to 4265 +/- 65 cal yr BP, suggesting that the eruption may have occurred slightly earlier than previously reported. The refined age and new geochemical reference dataset will facilitate the identification of the H2 tephra in other distal locations. The high concentration of glass shards in our peat sequence indicates that the H2 tephra may extend well beyond the Falkland Islands and we recommend future studies search for its presence across the sub-Antarctic islands and Antarctic Peninsula as a potentially useful chronological marker. Crown Copyright (C) 2021 Published by Elsevier Ltd. All rights reserved.

The Maherabad, Qaleh Zari, and Hired deposits in eastern Iran are porphyry (Cu-Au)-, Iron oxide copper-gold (IOCG)-, and reduced intrusion-related gold system (RIRGS)-type mineralization, respectively. They are located within the Lut block magmatic assemblage, which is the main metallogenic province in eastern Iran. The mineral assemblages and paragenesis of the deposits indicate that highest log fO2 and log fS2 contents belong to the Qaleh Zari deposit. In contrast, the lowest values of oxygen and sulphur fugacity are related to the RIRGS system in the Hired deposit. The Maherabad mineralization has moderate log fO2 and log fS2 contents relative to the Qaleh Zari and Hired deposits. Geochemically, these three deposits are related to different types of granitoids, which occurred within the short time interval from 37 to 41 Ma. The Maherabad and Qaleh Zari intrusions are related to oxidized magnetite-series granitoids, whereas the mineralization at Hired deposit is related to the reduced ilmenite-series granitoids. Magnetite-series intrusive rocks at Hired are barren. Intrusive bodies in the three studied sites are metaluminous, high-K calc-alkaline to shoshonitic, and formed in a volcanic arc setting. However, there are distinct differences in the radiogenic isotopic composition, content of some elements and elemental ratios reflecting the effect of different sources in the formation of intrusions. The reduced granite of the Hired deposit has the lowest Eu/Eu* of <0.7, P + Sr < 1000 ppm, and Sr/Y < 20 associated with (La /Yb)N < 12. Crustal contamination played an important role in magma evolution (87Sr/86Sri = 0.70627 and - epsilon Nd(t) = -2.60). P + Sr and Sr/Y contents in the productive oxidant magnetite-series intrusive rocks, such as the Maherabad and Qaleh Zari deposits, are more than 1500 ppm and 35, respectively. On this basis, petrological characteristic, geochemical indicator elements and mineral assemblage and paragenesis can be used for discrimination of productive and barren intrusions in the three different deposit types studied in this research. This can be used as an exploration criteria for the hydrothermal deposits associated with different magmatic intrusions in some areas.

ABSTRACT A previously undescribed small lenticular (~5 × 5 × 5 m) pegmatite, located near Wellington Lake in the NW part of the 1.08 Ga ‘A-type’ (anorogenic) ferroan Pikes Peak granite batholith, ~15 km SW of the South Platte pegmatite district in central Colorado, is concentrically zoned around a mostly monomineralic quartz core with interconnected miarolitic cavities. Major constituents of the Wellington Lake pegmatite are quartz, perthitic microcline, albite (variety cleavelandite), hematite, and biotite. Accessory minerals include fluocerite, bastnäsite, columbite, zircon (var. ‘cyrtolite’), thorite, and secondary U phases. Fluorite is conspicuously absent, although it is a common phase in the South Platte district NYF-type pegmatites, which are rich in niobium (Nb), yttrium (Y), fluorine (F), and heavy rare-earth elements (HREE). Notable for the Wellington Lake pegmatite are a small quantity of well-developed tabular crystals of fluocerite that reach up to 4 cm in diameter, with sub-mm epitaxial bastnäsite overgrowths, suggesting formation from F- and CO2-bearing solutions rich in light rare-earth elements (LREE), with decreasing a(F-)/a(CO32-) during the last crystallization phase. An Nd-isotope value of εNd1.08Ga = -1.6 for the fluocerite is within the range of εNd1.08Ga = -0.2 to -2.7 of the host coarse-grained, pink K-series Pikes Peak Granite (PPG), indicating that REE and other pegmatite constituents derived from the parental PPG magma. A calculation of total pegmatite composition based on whole-rock chemistry and volume estimates of the different pegmatite zones reveals an overall composition similar to the PPG with respect to Si, Al, Na, and K. Yet the pegmatite is depleted in Fe, Mg, Ca, Ti, Mn, and P, the high-field-strength elements (HFSE; Zr, Hf, Nb, Y, Th), and, most significantly, total REE compared to the PPG. Despite containing the LREE minerals fluocerite and bastnäsite, the lack of a net overall REE enrichment of the pegmatite compared to the PPG reflects the large amount of REE-poor silicate minerals forming the wall, intermediate, and core zones of the pegmatite. The calculated total pegmatite composition suggests that the pegmatite formed by the separation from the PPG magma of an F-poor H2O-saturated silicate melt depleted in REE and HFSE compared to the F-rich melts, which formed the NYF-type HREE-rich (LaN/YbN < 1) pegmatites in the South Platte district. Homogenization temperatures of < 500°C for possibly primary fluid inclusions in large quartz crystals from the core of the Wellington Lake pegmatite are consistent with recent models of pegmatite petrogenesis leading to nucleation controlled mega-crystal growth resulting from supercooling.

This Special Issue presents eight original contributions concerning ore deposits in China, Russia, and Chile [...]

Gadolinite, REE2FeBe2Si2O10, is a monoclinic orthosilicate member of the gadolinite supergroup of minerals and occurs in beryllium and rare earth element (REE) bearing granites, pegmatites, and some metamorphic rocks. Gadolinite from the White Cloud pegmatite, South Platte Pegmatite district, Colorado, USA, has been investigated and shows unusually variable REE compositions and distinct Be-Si disorder. Crystal structure and chemistry of two petrographically distinct gadolinite samples from this locality have been studied by electron microprobe chemical analysis, laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS), single-crystal X-ray diffraction (XRD), and micro-Raman spectroscopy. Within these samples, the gadolinite was found to range from gadolinite-(Y) to gadolinite-(Ce). Regions of nearly full occupancy of Fe at the M site, and partial substitution of Si for Be at the Q tetrahedral site, as well as substitution of Be for Si at the T site were observed, with up to 15% vacancy at the Fe site and up to 15% disorder between Be and Si at distinct tetrahedral sites elsewhere. The layered nature of the crystal structure allows for large variation of the radius of the cation at the A site which contains the REE. This study shows that Be may substitute for Si and that Be may be more abundant in geochemical systems than previously assumed.

This paper presents a detailed record of volcanism extending back to ∼80 kyr BP for southern South America using the sediments of Laguna Potrok Aike (ICDP expedition 5022; Potrok Aike Maar Lake Sediment Archive Drilling Project - PASADO). Our analysis of tephra includes the morphology of glass, the mineral componentry, the abundance of glass-shards, lithics and minerals, and the composition of glass-shards in relation to the stratigraphy. Firstly, a reference database of glass compositions of known eruptions in the region was created to enable robust tephra correlations. This includes data published elsewhere, in addition to new glass-shard analyses of proximal tephra deposits from Hudson (eruption units H1 and H2), Aguilera (A1), Reclus (R1, R2-3), Mt Burney (MB1, MB2, MBx, MB1910) and historical Lautaro/Viedma deposits. The analysis of the ninety-four tephra layers observed in the Laguna Potrok Aike sedimentary sequence reveals that twenty-five tephra deposits in the record are the result of primary fallout and are sourced from at least three different volcanoes in the Austral Andean Volcanic Zone (Mt Burney, Reclus, Lautaro/Viedma) and one in the southernmost Southern Volcanic Zone (Hudson). One new correlation to the widespread H1 eruption from Hudson volcano at 8.7 (8.6–9.0) cal ka BP during the Quaternary is identified. The identification of sixty-five discrete deposits that were predominantly volcanic ashes (glass and minerals) with subtle characteristics of reworking (in addition to three likely reworked tephra, and one unknown layer) indicates that care must be taken in the analysis of both visible and invisible tephra layers to decipher their emplacement mechanisms.

We have determined the Hf isotopic compositions of 12 samples associated with the giant El Teniente Cu-Mo megabreccia deposit, central Chile. The samples range in age from ≥8.9 to 2.3 Ma and provide information about the temporal evolution of their magmatic sources from the Late Miocene to Pliocene. Together with previously published data, the new analysis indicates a temporal decrease of 10 εHf(t) units, from +11.6 down to +1.6, in the 12.7 m.y. from 15 to 2.3 Ma. These variations imply increasing incorporation of continental crust through time in the magmas that formed these rocks. The fact that the samples include mantle-derived olivine basalts and olivine lamprophyres suggests that these continental components were incorporated into their mantle source, and not by intra-crustal contamination (MASH). We attribute the increase, between the Middle Miocene and Pliocene, of crustal components in the subarc mantle source below El Teniente to be due to increased rates of subduction erosion and transport of crust into the mantle. The deposit formed above a large, long-lived, vertically zoned magma chamber that developed due to compressive deformation and persisted between ~7 to 4.6 Ma. Progressively more hydrous mantle-derived mafic magmas feed this chamber from below, providing heat, H2O, S and metals, but no unique “fertile” Cu-rich magma was involved in the formation of the deposit. As the volume of these mantle-derived magmas decreased from the Late Miocene into the Pliocene, the chamber crystallized and solidified, producing felsic plutons and large metal-rich magmatic-hydrothermal breccias that emplaced Cu and S into the older (≥8.9 Ma) mafic host rocks of this megabreccia deposit.

In the Dasovich rock-shelter, southwest Chubut, Argentina, obsidian artifacts make up > 50% of all the artifacts encountered. Although absent from the earliest Late Pleistocene (>= 11,800 cal yrs BP) occupational level in the site, they do begin to occur in the Early Holocene (>= 10,500 cal yrs BP). Obsidian is again absent from a younger Early Holocene (similar to 8500 cal yrs BP) level, but reappears in high abundance (>= 36% of all artifacts in each level and similar to 56% overall) in Middle and Late Holocene layers just below and overlying a 4-14 cm thick tephra layer produced by the H2 eruption of Hudson volcano at similar to 3870 cal yrs BP. We analyzed 19 of the 146 obsidian artifacts found in the site, including all 7 artifacts from the Early Holocene. Obsidian artifacts in the Early Holocene are derived from both a relatively local source (CIS-type from the Cisnes river valley similar to 120 to the northwest) and from a more remote source (PDA-types from Pampa del Asador similar to 270 km to the south). Only obsidian derived from remote sources (11 from PDA and 1 S-type from Sacanana similar to 400 km to the northeast) are found in the younger Middle and Late Holocene levels. The high abundance in the Middle and Late Holocene of obsidian derived from sources beyond the normal range for direct procurement by Patagonian hunter-gatherers (<150 km) suggests that this site may have been the locus of significant trade activity, consistent with its location close to the intersection of both historic trade routes and those previously proposed for the northward transport of PDA-type obsidian and southwestward transport of S-type obsidian. This activity began before the deposition of the tephra from the explosive H2 eruption of the Hudson volcano, which apparently did not produce any discontinuity in access to or use of obsidian in the area.

Introduction Mississippi Valley-Type (MVT) deposits are epigenetic zinc and lead deposits with minor copper hosted by dolostone, limestone, and locally sandstone in platform carbonate sequences inboard of major orogenic belts (Leach and Sangster, 1993; Leach et al., 2010). The Irankuh-Ahangaran Belt, which is the most important Pb-Zn mineralized zone of Iran, is situated within the Sanandaj-Sirjan tectonic zone. This belt is 400 km in length and 100 km in width. Three deposits including Irankuh mininig district, Ahangaran and Hosseinabad deposits were studied in this article (Fig. 1). The aim of this research is study of thermal gradient of subducted slab and age of formation of Pb-Zn deposits at Irankuh-Ahangaran belt, which is contrary information has been published so far on the type and their formation. Also, chemistry of ore-fluid in MVT deposits and impact of dolomitic and shale host rock on paragenesis, alteration, style, reserves and grade of deposits were discussed.These parameters will certainly be useful for exploration of the hidden MVT type deposits in the Irankou-Ahangan belt. Result and Discussion The Irankuh mineralization is hosted by Cretaceous dolostone and minor Jurassic shale rocks as epigenetic. The constructive thrust fault, which has been cut the Jurassic and Cretaceous host rocks, has played a major role in the rising of fluid and formation of mineralization. Mineralization is occurred as replacement and open space filling (fault breccia, veinlets and cavity of rock) in dolostone and breccia, veinlet and open space filling in shale host rock. The mineral assembelages are Fe-rich sphalerite, Fe- and Mn-rich dolomite, ankrite, galena, minor pyrite, bituminous, calcite ± quartz ± barite within carbonate host rocks, whereas quartz, pyrite, Fe-rich sphalerite, galena, minor chalcopyrite, low Fe-dolomite, bituminous, ± barite ± calcite are important primary minerals at clastic hos rocks (Karimpour et al., 2018). The Ahangaran deposit is very similar to Irankuh in host rock, alteration, paragenesis, and form of mineralization. Thrust fault has a constructive role for occurrence of mineralization and later destructive strike slip and normal faults have caused the displacement and destruction of mineralization. The Hosseinabad deposit is hosted by Jurassic shale, siltstone, and sandstone rocks as vein-veinlets, breccia and open space filling with structural control. Alteratin consists of silicification, chlorite, bituminous, and minor siderite, dolomite and ankerite similar to mineralization hosted by shale in Irankuh district. The mineral assemblages are galena, Fe-rich sphalerite, pyrite, chalcopyrite and minor phyrotite. Due to the lack of a proper dolostone unit in the Husseinabad deposit, mineralization is concentrated in particular areas with low-grade and low-reserves. Based on lithology, alteration, mineralization style, structural control by thrust faults, mineral paragenesis, and comparison with differnet types of Pb-Zn deposits, all deposits of Irankuh-Ahangaran belt are MVT-type. Deep-seated thrust faults formed during the early stages of subduction (~ 70 to 75 Ma), and played an important role in the upward migration of hydrothermal fluids from the basement to shallow depths. The geochronology of pyrite in Irankuh district based on Re-Os method indicate age of Irankuh Pb-Zn mineralization is 66.5 ± 1.6 Ma (Liu et al., 2019). Since the thrust faults have been cut the Jurassic to Upper Cretaceous rocks, and according to the absoulte age determined in Irankuh, the mineralization of this belt have been formed in the age range of 66 to 56 million years ago, mainly in the Paleocene (Fig. 15). Karimpour and Sadeghi (2018) suggested the hydrothermal fluid originated from the dehydration of a hot and young oceanic subducted slab, which liberated Pb, Zn, and other metals, and may have removed metals from rocks and organic material of the continental crust. More than 90% of all the water within the oceanic slab was released in the depth zone of the forearc region (depth of 30 to 50 km) (Karimpour and Sadeghi, 2018). In the depth zone, Mg-rich silicate minerals (such as antigorite, hornblende, chlorite, talc) have broken and the produced fluid is rich in Mg and Fe (Fig. 17). The ore-fluid of MVT deposits is Si-poor and Fe- and Mg- rich. Such fluid is mineralized on the hosts of the dolstone (Irankuh and Ahangaran) or Shale-Siltstone (Hossein Abad, and part of Irankuh and Ahangaran). There are significant differences in the type of paragenesis, alteration, shape, dimensions, reserves and grade in the deposits of this belt, which is controlled by the host rock type. Based on all lithological evidence, alteration, shape of mineralization, existence of thrust faults, mineral paragenesis and specific geological and geographic location, it can be used to exploration of the hidden MVT deposits in this belt. References Karimpour, M.H., Malekzadeh Shafaroudi, A., Esmaeili Sevieri, A., Shabani, S., Allaz, J.M. and Stern, C.R., 2018b. Geology, mineralization, mineral chemistry, and ore-fluid conditions of Irankuh Pb-Zn mining district, south of Isfahan. Journal of Economic Geology, 9(2): 267–294. (in Persian with English abstract) Karimpour, M.H. and Sadeghi, M., 2018. Dehydration of hot oceanic slab at depth 30–50 km: KEY to formation of Irankuh-Emarat Pb-Zn MVT belt, Central Iran. Journal of Geochemical Exploration, 194: 88–103. Leach, D.L. and Sangster, D., 1993. Mississippi Valley-type lead-zinc deposits. Geological Association of Canadian. Specific Paper, 40: 289–314. Leach, D.L, Taylor, R.D., Fey, D.L., Diehl, S.F. and Saltus, R.W., 2010. A Deposit Model for Mississippi Valley-Type Lead-Zinc Ores, Chapter A of Mineral Deposit Models for Resource Assessment. U.S. Geological Survey, Reston, Virginia, Scientific Investigations Report 2010–5070–A., 64 pp. Liu, Y., Song, Y., Fard, M., Zhou, L., Hou, Z. and Kendricke, M.A., 2019. Pyrite Re-Os age constraints on the Irankuh Zn-Pb deposit, Iran, and regional implications. Ore Geology Reviews, 104: 148–159.

Introduction The study area is located in the northeast of Iran (the Khorasan Razavi province) and 28 km northwest of Bardaskan city and in position of 57˚ 46΄ to 57˚ 52΄ latitude and 35˚ 21΄ to 35˚ 24΄ longitude. The study area is a part of Taknar zone. The Taknar geological-structural zone is situated in the north Central Iranian microcontinental and it is a part of Lut block (Fig.1). Taknar plutonic complex that is situated in the Taknar structural zone is located in the northern part of Iranian microcontinent. Materials and methods Chemical analysis of REE and minor elements of samples of the Bornaward diorites and gabbro’s took place in the ACME Lab. in Vancouver, Canada, by the ICP-MS method (Table. 1). For the Bornaward diorite dating by the U-Pb method, zircon grains of material remaining in the sieve, Bromoform were isolated from light minerals by cleaning and were isolated with a minimum size of 25 microns, and then studies took place in the Crohn's Laser Lab Arizona (Gehrels et al., 2008). Measurement of Rb, Sr, Sm and Nd isotopes and (143Nd/144Nd)i , (87Sr/86Sr)i ratios and ƐNd (T=552), ƐNd (T=0), ƐSr (T=552) and ƐSr (T=0) took place in radioisotope Laboratory, University of Aveiro in Portugal. Discussion Geology of study area The study area forms the central part of the Bornaward plutonic complex. This complex is a granitoid assemblage including granite, granodiorite, tonalite and granophyre.tscentral part has been formed by intermediate and basic intrusive rocks such as diorite, quartz diorite and gabbro units (Fig. 2). From the genetic point of view, the intermediate and mafic rocks of the Taknar plutonic complex does not have any relationship with granitoid rocks of this assemblage, and they are related to a similar magmatic phase but are separated from this granitoid assemblage. However, these mafic and intermediate units are older than granitic units at the rim of the complex that are called Bornaward granite. Petrography The main minerals in the diorite and quartz diorite rocks are plagioclase and hornblende and we can see biotite in the quartz dioritic rocks. Quartz exist as tiny grains and anhedral and in the matrix rock. The amount of Quartz in the quartz diorites is 5 to 20%. Plagioclases usually have normal zoning and are highly altered to sericite. Most of the plagioclases were saussuritized. Altered minerals resulted from plagioclase and hornblende are sericite, epidote, chlorite, zoisite and clinozoisite. The main minerals in the gabbro are pyroxene, hornblende, and fine grains plagioclase. Minor minerals in the rocks are apatite, magnetite and other opaque. The main texture of intermediate and mafic rocks in this assemblage is medium granular to coarse grain and especially in the intermediate rocks and gabbro rocks, we can see scattered poikilitic, intersertal, sub-ophitic and porphyroid texture. Geochemistry The area diorite and gabbro is located locate in Tholeiitic and Calc-alkaline series (Fig. 9). Shand index (Al2O3/(CaO+Na2O+K2O)) is obtained under 1.1, in Metaluminous field (Fig. 7) and I-type granite field (Chappell and White, 2001). Based on the TAS diagram (Middlemost, 1985), all the diorite and gabbro samples are located in diorite, gabbro-diorite and gabbro-norite groups (Fig. 6). The diorite and gabbro’s show enrichment LREE and low ascending pattern ((La/Yb)N =1.40-6.12 and LaN =12.26-75.81). U-Pb zircon geochronology Measurement of U-Th-Pb isotopes of the Bornaward diorite zircons of BKCh-03 sample (Table 2) show that its age is related to 551.96±4.32 Ma ago (Upper Precambrian (Neoproterozoic) (Ediacaran) (Fig. 14). Sr-Nd isotopes The (87Sr/86Sr)i and (143Nd/144Nd)i content of Bornaward diorite and gabbro rocks is located in the range of 0.7038 to 0.7135 and 0.51203 to 0.51214, respectively (Tables 3 and 4). It shows that the diorite and gabbro rocks can be affected by hydrothermal alteration because their (87Sr/86Sr)i is above (Fig. 16). The numeral amounts of ƐNd(T=552) of Bornaward diorite and gabbro are 2.0 to 4.0. Petrogenesis The Bornaward diorite and gabbro rocks show a widespread enriched pattern of Rb, U, K, Pb, La and Th elements than chondrite, while Ba, Ti, Ta, Sr and Nb elements show reduction as a result of fractional crystallization (Fig. 11). The rocks of this complex are formed at the continental margin and VAG environment (Fig. 18) which is related to the subduction of the oceanic crust that exists between the Iranian microcontinent and the Afghan Block. Results This assemblage with age of Late Neoproterozoic is the result of extensive magmatism in the northern part of the Iranian microcontinent due to Katangahi orogeny event. The similar magmatism in the northern part of the Iranian microcontinent is existing as Khaf-Kashmar-Bardeskan volcano-plutonic belt. Based on the geochemical investigations, the magmatism of these rocks has been tholeiitic and calk-alkaline and have formed the coexistent rocks with I-type granites. Alumina saturation index for intermediate and mafic rocks of Bornaward complex is metalumina. These are medium-K rocks and enriched in the LILE such as Rb, Pb, U and Th while depleted of the Nb, Ti, Ta, Sr and Ba. Therefore, it shows that these rocks have resulted from the mixing by the lower crust. The low (87Sr/86Sr)i Bornaward diorite and gabbro rocks and the numeral amounts of Ɛ0Nd(present) of these rocks from -0.2 to 4.0 show that production of such intrusive masses can be attributed to the source of upper mantle or contaminated lower continental crust. Environment of formation of the intermediate and basic rocks of the Bornaward plutonic complex is active continental margin and volcanic arc environment. References Chappell, B.W. and White, A.J.R., 2001. Two contrasting granite types: 25 years later. Australian Journal of Earth Sciences, 48(4): 489–499. Gehrels, G.E., Valencia, V.A. and Ruiz, J., 2008. Enhanced precision, accuracy, efficiency, and spatial resolution of U–Pb ages by laser ablation– multicollector– inductively coupled plasma-mass spectrometry. Geochemistry, Geophysics, Geosystems, 9(3): 1–13. Middlemost, E.A.K., 1985. Magmas and Magmatic Rocks. An Introduction to Igneous Petrology. Longman, London, New York, 266 pp.

Posthispanic lithic assemblages known for Central-Southern Chile are reviewed pointing to the need to make clearer these categories and create the methodological basis for starting the construction of such studies. In particularly we consider the analysis of lithic artifacts registered in one of the archaeological nodes operationally defined as part of a research project that takes as its central point the Fort San Luis de Alba, located in the area of the Cruces river in the province of Valdivia. Differences and continuities of pre- and post-contact industries are discussed, considering ideas and a simple scheme in with which to confront Mapuche-williche and Hispanic assemblages.