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Identification of the Permian E- MORB Type Basalts and Their Tectonic Significance from Shiyan Area, Wudang Mountain (武当山十堰地区二叠纪 E⁃ MORB 型玄武岩识别及构造意义)

ID: 5339
Year: 2019
Products: UP213;
Authors: Wang, Gang; Zhang, Han; Wang, Zongqi; Wu, Yudong; Wang, Dongsheng; Wang, Jiawei; (王, 刚;张, 晗;王, 宗;武, 昱;王, 东;王, 嘉;)
Journal: Geological Review (地质论评)

Detailed Large- scale lithofacies and structure field mapping and systematic test analysis reveals the Wudang Mountain is not unified Precambrian basement composition in South Qinling Orogeny, a suit of Mesozoic mélange were identified and determined in Huanglong—Fangtan and Yindongshan of Danjiangkou regions, which are located in between Shiyan and Liangyun faults. To further carry out the research on the mélange composition and their genesis directly affect the understanding of the Wudang Mountain orogeny and evolution. This study focuses on the genesis and epoch of the basalt block form Huanglong—Fangtan mélange. Whole rock geochemistry of these basalt blocks indicates they are sub alkaline tholeiitic series with typically characterized by middle concentrations of Ti, Zr, Hf, and Nd and Enriched mid ocean ridge basalt (E- MORB)- like rare earth element distribution patterns, trace element spider diagrams. In addition, the samples appear to have all originated from the low pressure and high degree of partial melting of spinel lherzolite and undergone the affected by enrichment of the mantle or subduction, ultimately resulting in an enrichment of high field incompatible elements provenance. Zircon U- Pb dating of basalts indicates a Middle Permian magmatic age. Most importantly, in combination with its regional geological characteristics and petrogenesis, the E- MORB type basalt blocks are constrained to a mid ocean ridge or seamount environment. Thus, an ocean basin exists in Shiyan area Wudang Mountain on Mid—Late Permian, which provides the basic information for re understanding the origin of Huanglong—Fangtan mélange and the tectonic attribute of the Phanerozoic in South Qinling Orogeny. (大比例尺构造—岩相填图和测试分析研究显示南秦岭武当山并非统一前寒武纪基底组成,在十堰和 两郧断裂之间的黄龙—方滩及丹江口银洞山等地区识别和厘定出一套中生代混杂岩带,开展混杂岩带内物质组成 和成因研究对正确认识武当山造山作用和区域构造演化有重要意义。 本文重点对武当山十堰黄龙—方滩地区混杂 岩带内玄武岩块体岩石成因及时代进行研究,岩石地球化学显示玄武岩块体为亚碱性拉斑玄武岩系列,具有中等 Ti、Zr、Hf、Nd 含量、弱轻稀土富集重稀土亏损的 E⁃MORB(Enriched Mid⁃ocean ridge basalt, 富集型洋中脊玄武岩)特 征,其岩浆为尖晶石二辉橄榄岩低压、高度部分熔融形成,源区可能受富集地幔或俯冲作用等影响导致富集高场强 不相容元素;锆石 U⁃Pb 测年表明其为中二叠世火山作用产物;区域地质特征及岩石成因研究共同指示该套 E⁃MORB 形成于洋中脊或附近海山环境。 综上,武当山十堰地区中—晚二叠世存在洋盆,该成果为理解十堰黄龙—方滩混杂 岩带成因机制和正确认识南秦岭显生宙构造属性提供了基础资料。)

Laser ablation ICP-MS geochronologic data from Granduc and Rock and Roll deposits, northwest British Columbia

ID: 5337
Year: 2019
Products: New Wave;
Authors: Mitchell G. Mihalynuk, Richard M. Friedman, and James M. Logan
Journal: Report

U-Pb geochronological results reported by Mihalynuk et al. (2019) for host rocks of the Rock and Roll and Granduc volcanogenic massive sulphide (VMS) deposits in the Iskut area of northwestern British Columbia are consistent with the Late Triassic age suggested by previous workers. Although a direct age determination is still lacking, they constrained mineralization to between ~222 Ma and < ~208 Ma for Granduc and 292 Ma to 186 Ma for Rock and Roll. The Late Triassic age may mark an important VMS mineralizing event within the submarine Stuhini arc, with implications for regional mineral exploration. Data from their study also provide constraints on two phases of superimposed deformation to between 210 Ma and 183 Ma. This GeoFile contains the full data set for detrital zircon samples summarized by Mihalynuk et al. (2019).

Geochemical and U-Pb and Sm-Nd isotopic constraints on the evolution of the Paleoproterozoic Ylitornio nappe complex, northern Fennoscandia

ID: 5336
Year: 2019
Products: New Wave;
Authors: Lahtinen, R;Huhma, H;Sayab, LS;
Journal: Advance online publication of the Bulletin of the Geological Society of Finland

The Ylitornio area in northern Finland is a typical example of a poorly outcropping, multiply deformed, complex Precambrian terrain. U–Pb, Sm-Nd and geochemical data from metavolcanic, metasedimentary and plutonic rocks combined with structural data define the lithodemic units and tectonostratigraphy of the area. The Mellajoki, Martimo, Hosiojoki, Kierovaara and Uusivirka suites form the Ylitornio nappe complex. Although main thrust stacking had occurred between 1.92– 1.89 Ga, later reverse faulting probably continued until 1.78 Ga. The Väystäjä bimodal volcanic rocks (2.09–2.05 Ga) from the Martimo suite are plume-related EMORB-OIB rocks formed during a continent breakup. The Kaskimaa greywacke of the Martimo suite is inferred to represent sedimentation in a deepening rift basin in the continental margin. The coeval Hosiojoki felsic rocks with A-type affinity and the Kierovaara suite granites (2.00–1.98 Ga) represent dry melting of a dominantly 2.1–2.05 Ga contaminated mafic underplate, and hydrous melting of both the mafic underplate and a refractory lower crust of Archean age, respectively. The older rocks of the Uusivirka suite are early-collisional (1.92–1.91 Ga) and derived from poorly mixed local sources, whereas younger psammite-pelite associations (Ristivuoma) are syn-collisional (1.91– 1.89 Ga) and derive from multiply recycled and thoroughly mixed sources. These rocks were deformed during continued collision with the development of foreland fold- and thrust belt.

Regularities of distribution of rare-earth elements in the Kivakka olivinite-gabbronorite layered intrusion (Northern Karelia)

ID: 5335
Year: 2019
Products: NWR213;
Authors: Bychkova Y.V., Bychkov D.A., Minervina E.A., Ivlev B.A., Tskhovrebova A.R., Kasyan A.K., Miklyaeva E.P.
Journal: Geochemistry (ГЕОХИМИЯ)

This study discusses the presentation of rare-earth elements (REEs) in the rocks of the Kivakka Olivinite-Gabbronorite Layered Intrusion in North Karelia. It aimed to provide a detailed petrographic description of the mineral parageneses that are present in the studied section of the massif. We found that the same minerals can manifest in both intercumulative and cumulative positions, depending on the degree of melt fractionation. At the same time, their quantity, which determines both the petrographic characteristics and the name of the rock, is not a criterion for their presence during the cumulus phases. We analyzed the concentrations of REEs in rocks and rock-forming minerals in the Kivakka massif, considering the REE concentration vertically and in the critical zones of contrast interbedding. In the study area, REEs are present as incoherent elements and accumulate in the residual melt, together with U, Th, Zr, and other incoherent elements, which make them a useful indicator of the degree of melt fractionation. In some cases, they can reflect different structural and genetic characteristics, such as the degree of cumulus density in a specific type of cumulative paragenesis. The presence of hydrothermal changes is best reflected by a change in Ce concentration. The preservation of the stability of the configuration and the slopes of the lines on the spider diagrams for REE indicate that the process of crystallization differentiation took place in a closed system.

Chemical composition of fluid inclusions in the Yorii jadeite–quartz rocks from the Kanto Mountains, Japan

ID: 5334
Year: 2019
Products: NWR193UC;ESI;
Authors: Fukuyama, M;Ogasawara, M;Kawamoto, T;
Journal: Journal of Mineralogical and Petrological Sciences,

Jadeite–quartz rocks from the Yorii area, the Kanto Mountains, central Japan occur as tectonic blocks within serpentinite mélange. Primary two–phase (liquid + vapor) aqueous fluid inclusions are observed in jadeite, quartz, albite and zircon. The fluids trapped in jadeite and quartz are H2O with and without CH4 and show a wide range of salinity (4.7 ± 1.1 wt% NaCleqv in jadeite; 3.4 ± 0.7 and 13.6 ± 2.0 wt% NaCleqv in quartz). In this study, we examined the chemical composition of fluid inclusions in quartz from jadeite–quartz rock to understand the characteristics of fluid, which related to the formation of the rocks in the subduction zone. The trace element concentrations of fluid inclusions determined with LA–ICP–MS are enriched in LILE, Li, B, HFSE and transition metals with LILE enriched and relatively HFSE depleted characteristics. These have elemental patterns similar to the HFSE–depleted fluid released from antigorite during subduction, though the orders of magnitude are different. It can be common chemical characteristics of fluid in a subduction zone. There are two possibilities of the chemical composition of the evolved fluid after the formation of jadeite–quartz rocks. HFSE from the fluid can be sequestered into jadeite–quartz rock prior to fluids moving up into a mantle wedge. This process lead the evolved fluids relatively depleted in HFSE and enriched in LILE. Other possibility is that the fluid has same chemical composition of fluid inclusion as the fluid is equilibrated with jadeite–quartz rocks during the jadeite–quartz formation. In both cases, fluid after the metasomatic formation of jadeite–quartz rocks can be relatively enriched in LILE and depleted in HFSE. Magmas generated in subduction zones exhibit distinctive geochemical features of LILE enrichment and HFSE depletion and this characteristic of arc magma can be explained by the behavior of HFSE during the formation of jadeite–quartz rocks.

Pore Structure, Wettability, and Their Coupled Effects on Tracer-Containing Fluid Migration in Organic-Rich Shale

ID: 5333
Year: 2019
Products: New Wave;
Authors: Yang, R;Liu, Y;He, S;Hu, Q;Zhang, L;
Journal: Petrophysical Characterization and Fluids Transport in Unconventional Reservoirs

The characteristics of pore structure and connectivity, as well as the shale wettability are critical petrophysical parameters for hydrocarbon storage and production in shale reservoirs. In this chapter, several typical core samples from the Longmaxi organic-rich shale formation are systemically assessed for the pore structure (connectivity) and wettability, as well as their coupled effects on fluid migration. Complementary approaches include mercury intrusion capillary pressure, contact angle measurement, spontaneous imbibition, as well as saturated diffusion with nanosized tracer migration mapped via laser ablation-inductively coupled plasma-mass spectrometry. Nanopores are dominant in Longmaxi organic-rich shale and pores and the permeability values are in the nanodarcy range. Longmaxi shale is strongly oil-wetting and moderately strong water-wetting. The predominant nanopore spaces and associated high tortuosity values, as well as the mixed wettability, strongly limit the diffusion behaviors of tracer-containing (including nonsorbing and sorbing) API brine in Longmaxi shale. Thus, due to the limited edge-connected pore spaces and low diffusion coefficients, the migration of hydrocarbons could be very slow from the shale matrix to hydraulically created fractures, with the initial high production of hydrocarbons from connected pore spaces near the sample edge.

An evolving subduction-related magmatic system in the Masara Gold District, Eastern Mindanao, Philippines

ID: 5332
Year: 2019
Products: NWR213;ESI;
Authors: Buena, A;Villaplaza, B;Payot, B;Gabo-Ratio, J;Ramos, N;Faustino-Eslava, D;Queaño, K;Dimalanta, C;Padrones, J;Tani, K;Brown, W;Yumul, G;
Journal: Journal of Asian Earth Sciences: X

The Masara Gold District in Eastern Mindanao, Philippines, is one of the most prolific gold provinces in the Philippines. Recent district-scale mineral exploration makes it possible to undertake geologic and geochemical studies and thus to yield better insights about the mineralization environment of the Masara Gold District. In the Masara Gold District, mineralization is hosted in andesitic rocks and multiple stocks of diorite intrusions. New U-Pb and whole rock K-Ar age dating of these host rocks reveal Eocene to Plio-Pleistocene ages for the magmatic suites. A new lithologic unit is proposed to accommodate the composite diorite phases associated with mineralization. Major and trace element geochemistry of these host rocks show that the Eocene magmatic suite exhibits a tholeiitic character while the diorite and subvolcanic andesite pulses of the Miocene are calc-alkaline in composition. Adakitic rocks were emplaced during the Late Miocene and Plio-Pleistocene. Mineralization in eastern Mindanao is associated with several intrusive events formed during the Oligocene to the Pliocene. The majority of these mineralization events is associated with calc-alkaline magmatic suites. Based on this study, epithermal gold mineralization in the Masara Gold District is closely related to the Late Miocene magmatic rocks which exhibit calc-alkaline and adakitic signatures.

Production origins and matrix constituents of spiculate pottery in Florida, USA: Defining ubiquitous St Johns ware by LA-ICP-MS and XRD

ID: 5331
Year: 2019
Products: New Wave;New Wave Research;
Authors: Bloch, L;Wallis, N;Kamenov, G;Jaeger, J;
Journal: Journal of Archaeological Science: Reports

Fine-grained “chalky” pottery containing microscopic sponge spicules is commonly recovered from archaeological sites throughout peninsular Florida, but many questions remain about its composition and origins. It is identified by different names, but most are associated with the St. Johns Type series. While it has been commonly assumed to originate in the St. Johns River drainage for which it is named, the prevalence of pottery with these characteristics in other locations has presented the likelihood of independent production in multiple places. In this study, we conducted LA-ICP-MS and XRD analysis of spiculate pottery from three Woodland period (ca. 1000 BCE to 1000 CE) sites, along with comparative clay samples, in order to characterize the raw materials and determine the geographic scope of production. Our results support the theory that this ware was independently produced across peninsular Florida. We further evaluate the hypothesis that this pottery was made with common wetland muck, through consideration of the material properties of muck constituents. This project emphasizes the importance of an ecosystem framework for understanding the long history of spiculate pottery production and its geographic spread within Florida.

Comparison of different sets of external standards for the LA-ICP-MS analysis of North American copper artifacts

ID: 5330
Year: 2019
Products: UP213;New Wave;
Authors: Dussubieux, L;Hill, M;Lattanzi, G;
Journal: Journal of Archaeological Science: Reports

Ideally, data produced by different laboratories performing the same type of analysis should be comparable. Comparability is important for exchanging data and the building of large databases in particular areas of research. Recently, the sourcing of North American copper using laser ablation – inductively coupled plasma – mass spectrometry (LA-ICP-MS) has developed significantly prompting questions about the compatibility of the different published data sets. Several parameters affect the compositions obtained with LA-ICP-MS. The selection of external standards is used with LA-ICP-MS to convert the raw counts for each element in concentrations expressed in ppm or %wt. Ideally external standards have a composition as close as possible to that of the analyzed object. Available standard reference materials are purer than archaeological artifacts and a combination of several of them is often selected to be able to quantify all the elements of interest. LA-ICP-MS laboratories use different sets of standard reference materials based on their experience, budget and availability. This paper will compare three sets of copper standard reference materials that are used routinely to measure the composition of North American copper artifacts. It will assess how they affect the concentration measurements in that type of samples and shows that impact on the concentrations of certain elements can be significant. Too low concentrations in the standards and possible heterogeneity could be two factors explaining discrepancies.

The Jequié Complex Revisited: a U-Pb Geochronological Reappraisal of the Geology and Stratigraphy of the Jequié-Itagi Area (Bahia, Brazil)

ID: 5329
Year: 2019
Products: UP213;New Wave;
Authors: Fernandes, P;Frantz, J;Rios, D;Davis, D;Porcher, C;Conceição, R;Coelho, R;
Journal: Anuário IGEO UFRJ

New geological and litogeochemical data plus La-ICP-MS U-Pb isotopic study on the Jequié Complex, or Jequié “Block”, a granulite facies terrain of the Northeastern São Francisco Craton, allowed to propose that a new lithodemic unit, the Volta do Rio Plutonic Suite, should be created as a lower rank unit. The Jequié Complex is defined here as an intrusive complex metamorphosed in the granulite facies, containing an assemblage of plutonic calc-alkalic mafic to intermediate rocks, fractionated trondhjemites, tonalites and granodiorites, besides normal calc-alkaline tonalites/ granodiorites and rare metasedimentary remnants plus two different sets of leucogranites. The Volta do Rio Plutonic Suite is proposed as a lower range lithodemic unit belonging to the Jequié Complex. It is composed of granodiorites and monzogranites with porphyroclastic texture, even- -grained granitoids and fine-grained granitoids, besides an association of amphibole-bearing leucogranites and mafic to intermediate rocks. The metamorphosed mafic, intermediate and felsic rocks of the Jequié Complex compose a Cordilleran-type magnesian calc-alkalic association, which age is 2.7 Ga. In contrast, all the metagranitoids of the Volta do Rio Plutonic Suite show a distinctive ferroan (“A-type”) geochemical signature and the mafic and intermediate rocks associated to metaleucogranites show alkaline characteristics and host locally high-grade REE mineralizations contained in chevkinite group minerals. In the Volta do Rio Plutonic Suite, the porphyroclastic granites were dated at 2.6 Ga.The provisional age of alkaline mafic rocks with magmatic-hydrothermal REE mineralizations and of possibly coeval leucogranites is 2.5 Ga. These mineralizations are inedit in the world and the obtained time frame indicates the need to re-evaluate the geology and metallogenic potential of the Jequié Complex by considering its primordial igneous nature and by screening out its “granulitic” or “charnockitic” nature.

A multidisciplinary approach for the quantitative provenance analysis of siltstone. Mesozoic Mandawa Basin, southeastern Tanzania)

ID: 5328
Year: 2019
Products: NWR193;
Authors: Caracciolo, L;Andò, S;Vermeesch, P;Garzanti, E;McCabe, R;Barbarano, M;Paleari, C;Rittner, M;Pearce, T;
Journal: Geological Society, London, Special Publications

This paper shows how heavy minerals and single-grain varietal studies can be conducted on silt sediments to obtain quantitative data as efficiently as for sand-sized sediments. The analytical workflows include heavy mineral separation using a wide grain-size window analysed through integrated optical analysis, RAMAN , QemScan, and zircon geochronology. Upper Raman-aided heavy mineral analysis on Jurassic-Cretaceous silt-sized sediments from the Mandawa basin in Tanzania reveals garnet and apatite to be the most common minerals together with zircon, tourmaline and subordinate rutile. Secondary diagnostic phases are titanite, staurolite and epidote. Multivariate statistics highlights the association among durable minerals (zircon, tourmaline and rutile) while garnet and apatite plot alone reflecting independence between the group of variables with garnet increasing in Jurassic samples. Raman data for garnet end-member analysis document different associations between Jurassic and Cretaceous samples. U-Pb dating of detrital zircon and their statistical integration with other datasets provide further insights on changes in the drainage systems. Early and late Pan-African terranes of the Mozambique belt and those of the Irumide Belt acted as main source of sediment during the Jurassic. Cretaceous sediments record a broadening of the drainage system reaching as far as the Usagran-Ubendian Belt and the Tanzanian Archean Craton.

Assessing mineral fertility and bias in sedimentary provenance studies: examples from the Barents Shelf

ID: 5327
Year: 2019
Products: UP213;New Wave;New Wave Research;ESI;
Authors: Flowerdew, M;Fleming, E;Morton, A;Frei, D;Chew, D;Daly, J;
Journal: Geological Society, London, Special Publications

The development of laser ablation techniques using inductively coupled plasma mass spectrometry has enabled the routine and fast acquisition of in situ U–Pb and Pb–Pb isotope ratio data from single detrital grains or parts of grains. Detrital zircon dating is a technique that is increasingly applied to sedimentary provenance studies. However, sand routing information using zircon analysis alone may be obscured by repeated sedimentary reworking cycles and mineral fertility variations. These biases are illustrated by two clear case studies from the Triassic–Jurassic of the Barents Shelf where the use of U–Pb geochronology on apatite and rutile and Pb–Pb isotopic data from K-feldspar is highly beneficial for provenance interpretations. In the first case study, U–Pb apatite ages from the (Induan – Norian) Havert, Kobbe and Snadd formations indicate an evolving provenance and identify possible episodes of storage within foreland basins prior to delivery onto the Barents Shelf. In the second case study, U–Pb rutile and Pb isotopic analyses of K-feldspar from the Norian–Pliensbachian Realgrunnen Subgroup provide a clear distinction between north Norwegian Caledonides and Fennoscandian Shield sources and suggest that a similar approach may be used to test competing models for sand dispersal for this Subgroup in regions farther north than this study.

Petrography, geochemistry and zircon U/Pb geochronology in igneous and metamorphic rocks, Cuiarí River, south of Guainía department, Colombia (Petrografía, geoquímica y geocronología U/Pb en circones de rocas ígneas y metamórficas a lo largo del Río Cuiarí en el sur del Departamento de Guainía, Colombia)

ID: 5326
Year: 2019
Products: NWR193UC;ESI;
Authors: Amed Bonilla; Thomas Cramer; Marc Poujol; Haroold Canom; José Alejandro Franco; Zeze Amaya
Journal: Revista Boletin de Geologia

In order to archive a better understanding of the Rio Negro-Juruena Geochronological Province (1.55-1.8 Ga) of the Amazonian Craton in SE-Colombia, we performed analyses of metamorphic, igneous and metasedimentary rocks outcropping in vicinity of the Cuiarí-River in the south of Guainía Department, near the Brazilian border. Based on field observations, mineralogical, geochemical and U/Pb LA-ICP-MS analysis in zircons, we could identify in the study area a Statherian basement which forms the Mitú Complex. It is composed by S-type granitoides, mainly monzogranitic to a lesser amount of quartz-monzodioritic to granodioritic, with calc-alkalic meta to peraluminosos, syncollisional to post orogenic characteristics and with U/Pb crystallization ages between 1760 to 1800 Ma. Additionally, in the study area more alkalic granitic intrusions with ovoidal K-feldspar phenocrysts forming a porphyritic texture outcrop where U/Pb zircon data suggest a crystallization age of ~1750 Ma (probably associated to the Tiquié Intrusion Suite defined in Brazil). Over this Statherian basement, a sedimentary sequence (which may represent the Upper Member of the Tunuí Group in Brazil) was deposited some 1750-1600 Ma ago, where metarenites and quartzites were impregnated by tourmalines as a result of metasomatic processes related to the intrusion of a porphyritic two-mica granite crystalized 1550 to 1600 Ma ago (associated with the Rio Içana Intrusive Suite in Brazil). Some ~1780 Ma old inherited zircons from the Mitú Complex in this intrusion suggest a magma origin by partial melting of cratonic cortical material triggered by sufficient water and low pressures for melting point decrease generating a magma enriched in fluids and incompatible elements like Rb and K. Younger paragneisses with detrital zircon ages between 1000 to 1800 Ma close the Precambrian geological cycle identified in this area of Colombia. Its mineralizing potential as well as a tectonic and paleogeographic history still to be deciphered in detail. (Para avanzar en la comprensión de la Provincia Geocronológica Rio Negro-Juruena (1,55-1,8 Ga) del Cratón Amazónico en el suroriente colombiano se analizaron rocas metamórficas, ígneas y meta-sedimentarias aflorantes alrededor del Río Cuiarí en el sur del Departamento de Guainía, zona limítrofe Colombia-Brasil. Con base en observaciones de campo, análisis mineralógicos, geoquímicos y edades LA-ICP-MS U/Pb en circones se identificó en el área un basamento Estateriano (formando aquí el Complejo Mitú) compuesto de granitoides tipo S, principalmente monzograníticos y en menor proporción cuarzo-monzoniticos a granodioriticos, calcoalcalinos, meta a peraluminosos, con características de granitos sin-colisiónales a pos-orogénicos con edades U/ Pb de cristalización entre 1760 y 1800 Ma. Adicionalmente afloran intrusivos graníticos más alcalinos de textura porfirítica con fenocristales ovoides de feldespato potásico y una edad de cristalización U/Pb en circones de ~1750 Ma (probablemente asociado a la Suite Intrusiva Tiquié definida en Brasil). Sobre este basamento Estateriano fue depositada una secuencia sedimentaria (que pertenece al Grupo Tunuí) entre 1750 y 1600 Ma descritas como metarenitas y cuarcitas con turmalina, probablemente como miembro superior del Grupo Tunuí que fue afectado por metasomatismo relacionado con la intrusión de un granito porfirítico de dos micas con una edad de cristalización entre 1550 y 1600 Ma (asociado a la Suite Intrusiva Rio Içana). Circones heredados con edades del Complejo Mitú ~1780 Ma en este intrusivo sugieren un origen del magma por fusión parcial de material cratónico en presencia de suficiente agua y presión no demasiada alta para una temperatura de fusión relativamente baja que permitieron formar un magma enriquecido en fluidos y elementos  incompatibles como Rb y K. Paragneises con edades en circones detríticos más jóvenes entre 1000-1800 Ma, cierran el ciclon geológico precámbrico reconocible en esta área de Colombia con un potencial mineralizante y desarrollo tectónico y paleogeográfico todavía por determinar en detalleorms the Mitú Complex.)

Octahedral substitution in beryl from weakly fractionated intragranitic pegmatite Predne Solisko, Tatry Mountains (Slovakia): the indicator of genetic conditions

ID: 5325
Year: 2019
Products: New Wave;New Wave Research;
Authors: Bacik, P;Fridrichova, J;Uher, P;Rybar, S;
Journal: Journal of GEOsciences

Crystal-chemical properties, and octahedral substitution role in particular, of beryl from weakly fractionated intragranitic pegmatite Predné Solisko, Vysoké Tatry Mts. (Slovakia) is described in detail. The studied beryl was found in granitic pegmatite derived from biotite I-type granodiorite. It has a weakly zoned core with variable Fe and Mg contents but constantly high Na. The rim zone shows weak irregular chemical zoning with low Na and Mg, the latter dominating over Fe. The total Al content varies between 1.77 and 1.87 apfu; Al is substituted by Fe (0.03-0.07 apfu) and mostly by Mg (0.02-0.13 apfu). The decrease in octahedral site charge is mostly balanced by Na (0.05-0.30 apfu). However, the Na content in the rim is insufficient for balancing octahedral Fe + Mg, implying that at least a part of Fe is ferric. The c/a ratio is typical of “normal” beryl but its low value suggests dominant octahedral substitution. The 2b channel site is occupied by Na, Ca, REE and Sr. At the larger 2a site, Cs is clearly the most abundant (up to 3919 ppm). Water is present as both type I and type II but with large dominance of doubly coordinating H2O type II suggesting relatively fluid-rich genetic environment. The composition of beryl reflects the source rock of pegmatitic melt; I-type granitoids are generally enriched in Mg compared to S-type ones and consequently, the CNaOMgC□-1OAl-1 substitution may play a more important role in beryl from I-type derived pegmatites such as Predné Solisko. The geological position of the studied intragranitic pegmatite excludes the possibility of contamination from the host rock and the beryl chemistry, therefore, reflects faithfully the pegmatitic melt composition.

Mineralogy of Eocene Fossil Wood from the “Blue Forest” Locality, Southwestern Wyoming, United States

ID: 5324
Year: 2019
Products: UP213;New Wave;
Authors: Mustoe, G;Viney, M;Mills, J;
Journal: Geosciences

Central Wyoming, USA, was the site of ancient Lake Gosiute during the Early Eocene. Lake Gosiute was a large body of water surrounded by subtropical forest, the lake being part of a lacustrine complex that occupied the Green River Basin. Lake level rises episodically drowned the adjacent forests, causing standing trees and fallen branches to become growth sites for algae and cyanobacteria, which encased submerged wood with thick calcareous stromatolitic coatings. The subsequent regression resulted in a desiccation of the wood, causing volume reduction, radial fractures, and localized decay. The subsequent burial of the wood in silty sediment led to a silicification of the cellular tissue. Later, chalcedony was deposited in larger spaces, as well as in the interstitial areas of the calcareous coatings. The final stage of mineralization was the precipitation of crystalline calcite in spaces that had previously remained unmineralized. The result of this multi-stage mineralization is fossil wood with striking beauty and a complex geologic origin.

Paragenesis of Gold Mineralization and Integrated Exploration Techniques of the Kiyuk Lake Project, Kivalliq Region, Nunavut, Canada

ID: 5323
Year: 2019
Products: NWR193;
Authors: Jones, S;
Journal: Thesis

Exploration for gold in Nunavut has primarily focused in Archean greenstone belts in the north and coastal regions of the territory, resulting in large areas of unexplored terrain. The Kiyuk Lake property is located in the underexplored southwest corner of the Kivalliq Region of Nunavut. Gold mineralization hosted by Proterozoic sediments is rare in the Canadian Shield, so this study endeavors to further the understanding of the enigmatic gold mineralization hosted in such sediments at the Rusty Zone at Kiyuk Lake. Mineralization is hosted by an immature lithic-wacke cut by thin intermediate dykes that are associated with hydrothermal breccias composed of Fe-carbonate, calcite, calcic-amphibole, Fe-sulphide, and Fe-oxide minerals. Textural and timing relationships suggest that the gold mineralization is post-sedimentary and syn- to post-intrusion of intermediate dykes. Stable isotope thermometry indicates mineralization took place between 450-600oC and geochronological studies suggest that the intrusion and mineralization occurred before or about 1.83 Ga. The mineralizing hydrothermal fluids are postulated to be volatile-rich aqueous solutions exsolved from a source of cooling magmas at depth that interacted with metamorphic fluids, previously in equilibrium with S-rich sedimentary rocks and/or basement rocks. Using basement breaching thrusts faults as conduits, fluid overpressurization along a later normal fault is thought to be the primary cause for the rapid depressurization and temperature decrease that caused Fe-sulphides minerals to precipitate, destabilizing the Au(HS)2- complex and finally depositing gold. Although sub-economic at present, the occurrence of gold in Paleoproterozoic basins such as Kiyuk Lake could signal a new timing of gold deposition for the Canadian Shield; however, exploration is challenged by extensive glacial deposits, limited outcrop, and restricted working seasons. Consequently, exploration must be planned to use integrated techniques to efficiently and effectively evaluate regional targets. Here I show a regional till survey, coupled with geophysical magnetic and gravity surveys and structural interpretation can be used to identify new regional scale targets by statically evaluating target scale and regional scale till surveys in conjunction with multi-element drill core chemistry to determine pathfinder element groups that clearly highlight the Rusty Zone outcropping mineralization and lead to the delineation of new anomalous areas.

Geochronology of Archean LCT Pegmatites

ID: 5322
Year: 2019
Products: UP213;New Wave;
Authors: Dittrich, T;Seifert, T;Schulz, B;Hagemann, S;Gerdes, A;Pfänder, J;
Journal: Archean Rare-Metal Pegmatites in Zimbabwe and Western Australia

The knowledge of the age of an LCT pegmatite mineralisation is one of the key exploration criteria as most of the major LCT pegmatite systems (e.g., Tanco, Greenbushes, Bikita, Wodgina) were formed in relative narrow time intervals within the earth history. In addition, the temporal and spatial relation-ships of the pegmatites to potential source granites, their crystallisation history and geotectonic settings are still under debate. For the evaluation of the petrogenesis and emplacement history we compared Meso- and Neo-Archean LCT pegmatites of the Zimbabwe (Bikita), Pilbara (Wodgina) and Yilgarn Cratons (Londonderry, Mount Deans, Cattlin Creek). Lepidolite and white mica and lepidolite are an abundant constituent of the investigated LCT pegmatites and potentially accessible for 40Ar/39Ar dating. The U–Pb dating of Ta–Nb–Sn oxides and cassiterite LA-ICPMS turned out to be suitable for the Neo-Archean pegmatites due to the widespread occurrence of these minerals as accessories in almost all samples. Furthermore, they are formed at a virtually constant level during pegmatite crystallisation from main crystallisation to late state hydrothermal overprint. The 40Ar/39Ar ages cover a large spectrum from Neoarchean (~2630 Ma) to Paleoproterozoic (~2316 Ma), and are verified by U/Pb tantalite/ columbite ages (~2870 to 2615 Ma, LA-ICP-MS) and by Th-U-Pb electron microprobe monazite ages (~2700 Ma; ~2500 Ma). Micas from the Yilgarn Craton yield Neoarchean cooling ages indicating an immediate cooling after crystallisation. In contrast, micas from the Zimbabwe (~2625 Ma) and Pilbara Craton (~2870 Ma) exhibit Paleoproterozoic cooling ages that significantly postdate initial crystallisation. This is in good agreement with petrographic data that suggests a post pegmatite hydrothermal overprint. Overall, our new age data are in good agreement with a previously postulated global major LCT pegmatite events between 2850 to 2800 Ma and 2650 to 2600 Ma. During this event specific geodynamic conditions (i.e. a super-continent assembly) and associated anormal high heat flow from the mantle enabled the global formation of large volumes of LCT pegmatites.

Geochronological and Geochemical Constraints on the Galinge Skarn Deposit

ID: 5321
Year: 2019
Products: NewWave;
Authors: Yu, M;
Journal: Silicone Composite Insulators

Galinge, the largest iron (Fe) polymetallic skarn deposit in the Qinghai province (NW China), is located in the Qiman Tagh metallogenic belt. At Galinge, post-collisional calc-alkaline metaluminous intrusions, including granodiorite, diorite and diorite porphyry dikes were emplaced into the Cambrian to Ordovician Qiman Tagh strata. Zircon U-Pb dating for granitic rocks yielded ca. 229 ‒ 217 Ma. Phlogopite coexisting with disseminated magnetite was dated to be 234.2 ± 3.5 Ma by Ar-Ar technique, indicating a close temporal magmatic-metallogenic relationship. Geochemically, the Qiman Tagh granodiorite is enriched in light earth element (LREE) with moderately negative Eu anomalies. Such geochemical data and zircon Hf isotopic data suggest that the studied granodiorite might be generated by low-degree partial melting of the amphibolite-facies metamorphosed rocks, whereas the Galinge diorite and diorite porphyry dykes were probably generated by higher degree of partial melting of the residual materials after granodioritic magma. We propose that the Galinge granitic magmatism and skarn Fe mineralization were formed under Late Triassic post-collisional extension after the closure of the Paleo-Tethys.

Experimental Investigation and Thermodynamic Modeling of the Distributions of Ag and Au Between Slag, Matte, and Metal in the Cu–Fe–O–S–Si System

ID: 5320
Year: 2019
Products: NWR193;Electro Scientific Industries;
Authors: Shishin, D;Hidayat, T;Chen, J;Hayes, P;Jak, E;
Journal: J. Sustain. Metall.

To assist in improving the recoveries of gold and silver in both primary production and metals’ recycling, the distributions of Ag and Au between slag, matte, and metal in the Cu–Fe–O–S–Si system have been investigated using an integrated experimental and thermodynamic modeling approach. The experimental technique involved high-temperature equilibration at selected temperatures and gas atmospheres, and rapid quenching followed up by measurement of phase compositions using microanalysis techniques. Electron probe X-ray microanalysis was used to measure the major element concentrations in the condensed phases. The laser ablation inductively coupled plasma mass spectrum technique was used to measure the concentrations of Ag and Au in slag. The experimentally determined distribution coefficient of Ag between matte and slag decreases with the increasing matte grade below approximately 70% Cu, but then increases with the increasing matte grade between 70 and 80% Cu. The experimentally determined distribution coefficient of Au between matte and slag decrease from log L = − 2.8 for approximately 63% Cu to approximately log L = − 3.8 at 76% Cu. Thermodynamic model parameters describing Ag and Au distributions have been derived following consideration of available data on slag/matte, slag/metal, and slag/matte/metal systems.

XRF and LA-ICP-MS studies of gold and silver artefacts from a 12–13th century CE tumulus in Senegal: Implications for the medieval African gold trade

ID: 5319
Year: 2019
Products: NWR193;ESI;TwoVol2;
Authors: Magnavita, S;Mertz-Kraus, R;
Journal: Journal of Archaeological Science: Reports

Silver and gold artefacts from a 12–13th c. CE tumulus in Senegal were recently analysed by means of XRF and LA-ICP-MS. The identification of major, minor and trace elements allowed gaining a rare insight into the composition of precious metals circulating in that part of Africa in medieval times. The results show that all objects were made of polymetallic alloys. Comparisons with analyses from other West African as well as North African and European silver and gold artefacts suggest that the metal from the studied objects most probably originate from outside West Africa. At least in the case of the gold artefacts, this is quite surprising, as we expected to come across pure West African gold. The results hint at a hitherto little known facet of the medieval African gold trade. It is concluded that, in addition to the acknowledged mass export of West African raw gold toward North Africa, there was also a thus far widely ignored traffic of alloyed gold (and silver) into West Africa.

Elemental analysis of Late Archaic copper from the McQueen Shell Ring, St. Catherine's Island, Georgia

ID: 5318
Year: 2019
Products: UP213;New Wave;
Authors: Hill, M;Lattanzi, G;Sanger, M;Dussubieux, L;
Journal: Journal of Archaeological Science: Reports

Excavations conducted at the McQueen Shell Ring on St. Catherine's Island off the coast of Georgia recovered several fragments of a copper artifact. These fragments represent an artifact made from a thin sheet of copper, and were recovered from a Late Archaic feature with calibrated radiocarbon dates placing its use between 2300 and 1800 cal. BC. Seven of these fragments were analyzed at the Elemental Analysis Facility of the Chicago Field Museum of Natural History to determine elemental composition with the intent of identifying probable sources for the copper from which the artifact was manufactured. Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) was used to collect elemental composition data for these seven fragments as well as from geological source samples representing Lake Superior, the southern and central Appalachians, and the Canadian Maritimes. Several statistical analyses were performed on the resulting data by varying test assumptions and parameters. All analyses place the most likely source for the Georgian artifact in the Lake Superior region far to the north rather than in the closer sources of the Appalachians, requiring a more complex explanatory framework to account for this long distance interaction or acquisition.

Iron is neurotoxic in retinal detachment and transferrin confers neuroprotection

ID: 5317
Year: 2019
Products: NWR213;New Wave;
Authors: Daruich, A;Le Rouzic, Q;Jonet, L;Naud, MC;Kowalczuk, L;Pournaras, JA;Boatright, JH;Thomas, A;Turck, N;Moulin, A;Behar-Cohen, F;Picard, E;
Journal: Sci Adv

In retinal detachment (RD), photoreceptor death and permanent vision loss are caused by neurosensory retina separating from the retinal pigment epithelium because of subretinal fluid (SRF), and successful surgical reattachment is not predictive of total visual recovery. As retinal iron overload exacerbates cell death in retinal diseases, we assessed iron as a predictive marker and therapeutic target for RD. In the vitreous and SRF from patients with RD, we measured increased iron and transferrin (TF) saturation that is correlated with poor visual recovery. In ex vivo and in vivo RD models, iron induces immediate necrosis and delayed apoptosis. We demonstrate that TF decreases both apoptosis and necroptosis induced by RD, and using RNA sequencing, pathways mediating the neuroprotective effects of TF are identified. Since toxic iron accumulates in RD, we propose TF supplementation as an adjunctive therapy to surgery for improving the visual outcomes of patients with RD.

Morphology and Chemistry of Zircons from the Paleoproterozoic Cu (±Mo±Au) Hosting Granitoids of Malanjkhand Mine Area, Central India

ID: 5316
Year: 2019
Products: UP213;
Authors: Arya, D;Gupta, S;Kumar, S;Broska, I;Vaculovic, T;
Journal: J Geol Soc India

Morphology and chemistry of zircons from Paleoproterozoic granitoids (~2470 Ma) of Malanjkhand mine area, central India have been used to understand nature of parental magma and its evolutionary history. External morphology of nonmetamict zircons belongs to S3, S1-2, G1, P2, S24 and S25 subtypes of Pupin’s typological scheme, which crystallized in a calc-alkaline, metaluminous hybridizing magma. The Zr/Hf ratios of zircons point to a low degree of differentiation of parental magma. Most zircons bear low sum of rare earth elements (∑REE<700 ppm) indicating late stage of crystallization, whereas a zircon with anomalously high LREE and ∑REE probably indicates at an early stage of its crystallisation in the absence of other REE bearing accessory phases or might have been influenced later by hydrothermal fluids. The Nb content of zircons is similar to those commonly formed in high-K, calc-alkaline granitoid magma series. The zircon (Th/U>1) with high ∑REE (5019 ppm) and Ti (56 ppm) contents provides zircon crystallization temperature (TZr) of 938°C suggesting its crystallisation in a relatively high-T intermediate magma composition. However, zircons with Th/U<1 bear Ti content below the detection limit (33 ppm) due to their crystallization in a relatively more evolved aluminous melt fraction of parental calc-alkaline magma. All zircons exhibit positive Ce- and negative Eu-anomalies, which probably indicate mildly oxidising magma condition of zircon crystallization synchronous with plagioclase.

The sandstone-hosted Osen lead deposit, Norway: new Pb isotope evidence for sourcing in the underlying granitoid basement

ID: 5315
Year: 2019
Products: NWR193;ESI;
Authors: Bjørlykke, A;Bingen, B;Billström, K;Kooijman, E;
Journal: NJG

The Osen deposit is one of several Pb–Zn deposits in Baltoscandia, hosted in Lower Cambrian sandstone, unconformably overlying a Precambrian granitoid basement and overlain by Caledonian nappes of the Lower Allochthon. In the Osen area, the Palaeoproterozoic Trysil granite (1673 ± 8 Ma) shows evidence of weathering below the unconformity. New Pb isotope data, collected by Laser Ablation Multi-Collector Inductively Coupled Plasma Mass Spectrometry (LA–MC–ICP–MS) on K-feldspar from six samples of the Trysil granite, provide an improved internally consistent model for the age and sourcing of the Osen deposit. Data spread along the published whole-rock errorchron of the Trysil granite form two populations. The least radiogenic of these, defined by a cluster of 10 data points (average 206Pb/204Pb = 16.51 and 207Pb/204Pb = 15.37), is interpreted to represent the initial ratio of the granite. Published isotope data of Pb in galena in the Osen deposit (20.24 < 206Pb/204Pb < 20.49, 15.85 < 207Pb/204Pb < 15.89) plot on a reference line including this K-feldspar cluster and whole-rock data of the Trysil granite, as it was c. 540 Myr ago. This distribution suggests that the Osen deposit was generated shortly after deposition of the sandstone in the Early Cambrian (c. 541–511 Ma). Lead was released by weathering of the granite basement during development of the sub-Cambrian peneplain. It therefore discards alternative models involving Caledonian events in either Ordovician or Silurian time.

Microgranular Heterogeneity of Quartz Glass

ID: 5314
Year: 2019
Products: New Wave;
Authors: Nasyrov, R;Bodunov, B;Artem’ev, D;
Journal: Glass Ceram

A physico-chemical analysis is performed of technologies for producing quartz grit and making glass from it. Experimental production of glass from grit was performed. The conditions of melting made it possible to form microgranular inhomogeneity with a volumetric network of boundaries in a glass ingot decorated with impurities. Optical, electron microscopic, and mass spectroscopic studies confirm the new hypothesis of microgranular heterogeneity appearing in quartz glass. The results of these studies can be taken into account when making high-quality ultrapure quartz glass for science-intensive industries.

The Permian-Triassic Intracratonic Magmatic Corridor of the province of La Pampa, Argentina: new ages U-Pb SHRIMP, isotopic composition of Hf and geodynamic implications (El Corredor Magmático Intracratónico Pérmico-Triásico de la provincia de La Pampa, Argentina: nuevas edades U-Pb SHRIMP, composición isotópica de Hf e implicancias geodinámicas)

ID: 5313
Year: 2019
Products: UP213;New Wave;
Authors: Chernicoff, C;Zappettini, E;Santos, J;McNaughton, N;
Journal: Mexican Magazine of Geological Sciences (Revista Mexicana de Ciencias Geológicas)

A study and review of the magmatic units that make up the PermianTriassic Intracratonic Magmatic Corridor of La Pampa (CMPT-LP), south-central Argentina, has been carried out. New U-Pb SHRIMP ages, Hf isotopic composition, and chemical composition of some units of the CMPT-LP have been obtained, i.e. 1) Chacharramendi Syenogranite, age 254.7 ± 1.3 Ma (Late Permian, Lopingian), Hf model age of 1640 Ma with εHf average of -5.68; 2) Lihue Calel Rhyolite, 239.3 ± 1.5 Ma (Middle Triassic), Hf model age of 1640 Ma with εHf average -5.56. This indicates that the two dated units were crystallized from a mantle-derived melt that incorporated crust of late Statherian up to Calymmian age, taking also into account a Nd model age of 1483 Ma for the more distal (southeasternmost) sector (López Lecube Granite) of the CMPT-LP obtained by other authors. New geochemical data reported here, analyzed together with previous geochemical data, denote the anorogenic signature –intraplate environment– of the CMPT-LP magmatic corridor, highlighting its consistency with A1-type granites due to the similarity of their sources with those from which the oceanic island basalts (OIB) derive, as evidenced, e.g., by Y/Nb ratios < 1.2. The classification of the rocks of the CMPT-LP mainly within the high potassium type is also consistent with its occurrence in an intraplate tectonic environment. The magmatism in the CMPT-LP has been considered as part of the Choiyoi Group, which is also related to late Permian to Early Triassic extension. Nevertheless, there is a marked contrast between the anorogenic environment of the CMPT-LP and the orogenic context of the Choiyoi Magmatic Arc. For this reason, the convenience of excluding the CMPT-LP from the Choiyoi Group is analyzed. In addition, the tectonic frames of the orogenic belts adjoining the CMPT-LP –San Rafael (or Sanrafaelic, or Choiyoi Arc-retroarc) and Northpatagonian Gondwanide belts– are compared briefly. (Se ha realizado un estudio y revisión de las unidades magmáticas que integran el Corredor Magmático Intracratónico Pérmico-Triásico de La Pampa (CMPT-LP), centro-sur de Argentina. Se dan a conocer nuevas edades U-Pb SHRIMP, composición isotópica de Hf y composición química de algunas unidades integrantes del CMPT-LP: 1) Sienogranito Chacharramendi, edad 254.7 ± 1.3 Ma (Pérmico tardío, Lopingiano), edad modelo Hf de 1640 Ma con εHf promedio de -5.68; 2) Riolita Lihue Calel, 239.3 ± 1.5 Ma (Triásico Medio), edad modelo Hf de 1640 Ma con εHf promedio de -5.56. Esto indica que las dos unidades datadas fueron cristalizadas a partir de un fundido mantélico que incorporó corteza de edad statheriana tardía hasta calymmiana, tomando en cuenta también la edad modelo Nd de 1483 Ma del sector más distal (sudoriental) (Granito López Lecube) del CMPT-LP obtenida por otros autores. Nuevos datos geoquímicos aquí aportados, analizados junto con datos geoquímicos previos, denotan la impronta o huella anorogénica –ambiente de intraplaca– del corredor magmático CMPT-LP, destacándose su consistencia con los granitos del tipo A1 debido a la similitud de sus fuentes con aquéllas de las que derivan los basaltos de islas oceánicas (OIB), como queda evidenciado, p. ej., en los cocientes Y/Nb <1.2. La pertenencia de las rocas del CMPT-LP mayoritariamente al tipo de alto potasio también es consistente con su ocurrencia en un ambiente tectónico de intraplaca. El ambiente anorogénico del CMPT-LP contrasta con aquél de la etapa tardía del Grupo Choiyoi propiamente dicho, que si bien también está asociada a extensión pérmica tardía – triásica temprana, ocurre en el contexto orogénico propio del Arco Magmático Choiyoi. Por tal razón se analiza la conveniencia de excluir el CMPT-LP del Grupo Choiyoi, en el que hasta ahora estaba incluido. Asimismo se comparan brevemente los marcos tectónicos de las fajas orogénicas lindantes del CMPT-LP: fajas de San Rafael (o Sanrafaélica, o Arco-Retroarco Choiyoi) y Gondwánides Norpatagónicos.)

Distinct sulfur saturation histories within the Palaeogene Magilligan Sill, Northern Ireland: Implications for Ni-Cu-PGE mineralisation in the North Atlantic Igneous Province

ID: 5312
Year: 2019
Products: UP213;New Wave;New Wave Research;
Authors: Lindsay, J;Hughes, H;Smyth, D;McDonald, I;Boyce, A;Andersen, J;
Journal: Can. J. Earth Sci.

The ~60 m thick Magilligan Sill is part of the British Palaeogene Igneous Province in the North Atlantic. The sill comprises layers of dolerite and olivine gabbro, and it intrudes a thick sequence of Mesozoic mudstones and marls, which are locally baked at the sill margins. Since 2014, the sill has been an exploration target for orthomagmatic Ni-Cu-PGE sulfide mineralisation analogous to the Noril’sk-Talnakh intrusion in Russia. We present new petrological, geochemical and S-isotope data to assess the prospectivity of the sill and the underlying magmatic plumbing system. Most sulfides in the dolerite portions of the sill are < 50 μm in size and comprise only pyrite with PGE abundances below detection limit. In the olivine gabbros, > 150 μm size pentlandite, chalcopyrite and pyrrhotite grains contain < 4 ppm total PGE, 1 460 ppm Co and 88 ppm Ag. Pyrite from the dolerites have δ34S ranging from -10.0 to +3.4 ‰ and olivine gabbro sulfides range from -2.5 to -1.1 ‰, suggesting widespread crustal contamination. The S/Se ratios of sulfides in the dolerites and olivine gabbros range from 3 500 to 19 500 and from 1 970 to 3 710, respectively, indicating that the latter may have come from upstream in the magma plumbing system. The Magilligan Sill records multiple injections of mafic magma into an inflating sill package, each with distinct mechanisms towards S-saturation. Whilst the sulfide minerals in the sill do not constitute significant mineralisation themselves, detailed in-situ studies highlight a divergence in S-saturation histories, and suggest that a larger volume of olivine gabbro sulfides at depth may be prospective.

Geochronology and Geochemistry of Igneous Rocks in the SE Lesser Xing’an Range (LXR), Northeast China: Petrogenesis and Implications for the Early Mesozoic Tectonic Evolution

ID: 5311
Year: 2019
Products: UP213;New Wave;
Authors: Jinhua, Q;Cui, L;Jinfu, D;
Journal: Can. J. Earth Sci.

We present systematic U-Pb age data collected by laser ablation multicollector inductively coupled plasma mass spectrometry (LA-ICP-MS), precise geochemical data and Nd isotope data for igneous rocks from the SE LXR. The results indicate that the formation ages as follows: Maojiatun alkaline granite, 207.2±0.84 Ma and 204.6±0.93 Ma; porphyritic diorite, 164.5±0.97 Ma; and Tieli alkali-feldspar granite, 186.7±1.50 Ma. The alkaline granite has high silicon, potassium, alkali and TFeO contents, it is enriched in high field strength elements (HFSEs), Zr, Hf, Th, Rb, and U; is depleted in Ba, Sr, Nb, Ta, P, Ti, etc.; and has high ratios of 10000*Ga/Al. It shows an A2-type granite affinity. The Tieli alkali-feldspar granite has high total alkali contents and is enriched in HFSEs and rare earth elements (REEs) and depleted in Sr, Ba, Ti, and P, and shows varying degrees of alkalinity. Rocks from SE LXR display similar ɛNd (t) values with corresponding to Nd model ages of 813 to 1095 Ma. The igneous rocks from the SE LXR are proposed to be derived from melting of the Neoproterozoic lower crust and potential magma mixing with ancient crystalline basement. The formation of the Maojiatun alkaline granite occurred in response to a postorogenic event following the closure of the Paleo-Asian Ocean. However, The SE LXR exhibited an extensional back-arc tectonic setting in the Early Jurassic. The Middle Jurassic porphyritic diorite could be related to the temporary stagnation of the westward subduction of the Paleo-Pacific plate.

Effects of the 2011 Missouri River flood on walleye natal recruitment and habitat use in Lake Sharpe, South Dakota

ID: 5310
Year: 2019
Products: New Wave;New Wave Research;
Authors: Radigan, W;Carlson, A;Fincel, M;Graeb, B;
Journal: Journal of Freshwater Ecology

Floods affect fish populations in the short term (e.g. entrainment, mortality) and long term (e.g. recruitment, habitat availability), but oftentimes long-term effects are overlooked. In 2011, a catastrophic flood with record peak flows (4,200 m3/s) occurred in Lake Sharpe, a mainstem Missouri River reservoir. The flood’s immediate impacts on the Lake Sharpe walleye (Sander vitreus) population have been documented, but long-term effects on natal recruitment and habitat use have not been assessed. We used otolith chemistry to evaluate spatial patterns in walleye natal recruitment and late-summer (i.e. July − September) habitat use in years before, during, and after the flood to gain insight into long-term flood impacts on the Lake Sharpe walleye population. From 2004 to 2013, all walleye hatched in embayments and main channel habitats as opposed to stilling basins or tributaries, and the majority of age ≥ 1 fish (i.e. age-1 or older) used the former habitats in late summer. During the flood year, natal recruitment remained stable relative to pre-flood levels in embayments (26% pre-flood, 20% during flood) and main channels (74% pre-flood, 80% during flood). Habitat use of age ≥ 1 walleye was generally unaltered by the flood as it remained consistent in embayments and main channel habitats before, during, and after the disturbance. Hence, the Lake Sharpe walleye population was largely unaffected by the flood in terms of natal recruitment and habitat use. Our results highlight the resilience of the Lake Sharpe walleye population to a catastrophic flood, providing fisheries professionals with an otolith chemistry approach for quantifying flood effects on natal recruitment and habitat use and developing spatially informed management approaches (e.g. habitat protection/rehabilitation, harvest regulations).

Geochronology and Petrochemistry of Volcanic Rocks in the Xaignabouli Area, NW Laos

ID: 5309
Year: 2019
Products: NWR193;ESI;
Authors: Shi, M;Wu, Z;Liu, S;Peng, Z;Guo, L;Nie, F;Xu, S;
Journal: J. Earth Sci.

An integrated study of zircon U-Pb geochronology and petrochemistry, together with zircon Lu-Hf isotopes, has been carried out on the basaltic-andesitic tuff and volcanic breccia from the Nam Hang Formation and andesitic tuff from the Muang-Nan Formation in the Xaignabouli area, which had been mapped as the Permian-Early Triassic on the 1 : 1 000 000 geological map or Late Carboniferous on the 1 : 200 000 geological maps. Zircon U-Pb dating of three samples yielded weighted mean ages of 235±2.6, 232±1.4 and 278±2.8 Ma, respectively, suggesting a Late Triassic origin for the Nam Hang Formation and an Early Permian origin for the Muang-Nan Formation. Geochemically, they are characterized by depletions in HFSEs (e.g., Nb, Ta, Ti) and high LILE/HFSE ratios, and they have positive zircon εHf(t) values of 8.7-15.9, which exhibits the continental arc volcanic affinity and partial melting of subducting oceanic slab in the magma source. Combined with spatial occurrence of the volcanic rock and existing geochronological and geochemical data, we suggest that the Xaignabouli-Luang Prabang volcanic belt can be linked to the Loei-Phetchabun belt. The Permian-Triassic volcanic rocks in this belt might be a product of the Nan back-arc basin eastward subduction.