scholarly journals Stable isotope (δD, δ18O) data on the structural water of two sericite samples from the Cu-Au high-sulphidation deposit Chelopech, Bulgaria – a tentative study

2021 ◽  
Vol 50 (3) ◽  
pp. 65-74
Author(s):  
Nikolay Piperov ◽  
Sylvina Georgieva
Keyword(s):  
Carbon Dioxide ◽  
Mineral Assemblage ◽  
Meteoric Water ◽  
Underground Mining ◽  
Alteration Zone ◽  
Structural Water ◽  
Thermal Fractionation ◽  
Ore Mineralization ◽  
Host Rocks ◽  
Isotopic Measurements

The epithermal high-sulphidation Cu-Au Chelopech deposit is characterized by a well-developed and well-traceable hydrothermal footprint manifested in the volcanic host rocks. The economic ore mineralization is embedded in the strong silicification, included among the advanced argillic zone of alteration, smoothly transitioning to quartz-sericite alteration that evolves into widespread propylitics. The quartz-sericite alteration zone is accessible for exploration only in underground mining galleries and exploration drillings. The main mineral assemblage in this zone is quartz, sericite, pyrite, minor rutile/anatase and relics of apatite and feldspar. According to XRD data from the studied samples, sericite was defined as illite and muscovite/sericite 2M1 polytype. The abundance of heavy stable isotopes (D, 18O) in the structural water of two sericite samples is the object of this study. A special attention was paid to the separation of extraneous waters from the structural one by thermal fractionation. The extracted structural water was converted to hydrogen and carbon dioxide before the isotopic measurements. The obtained results, put into a δD vs. δ18O plot, indicate that sericite structural water is “heavier” than meteoric water, within uncertainty limits.

scholarly journals Eclogite-like rocks from Southern Pirin Mountains – preliminary results about petrology and time of formation

2021 ◽  
Vol 82 (3) ◽  
pp. 61-63
Author(s):  
Lyubomirka Macheva ◽  
Philip Machev ◽  
Rossitsa Vassilevа ◽  
Yulia Plotkina
Keyword(s):  
Mineral Assemblage ◽  
Late Jurassic ◽  
Mineral Chemistry ◽  
Metasomatic Alteration ◽  
Preliminary Results ◽  
Icp Ms ◽  
Geological Map ◽  
Host Rocks ◽  
The Village

North-northeast of the village of Ilinden (Southern Pirin Mnt.) three eclogite boudins were separated on the geological map in scale 1:50 000 (Sarov, 2010). The rocks belong to the Slasten lithotectonic unit. The mineral assemblage and mineral chemistry do not allow these rocks to be classified as eclogites. They can be considered as eclogite-like ones, formed by postmagmatic-metasomatic alteration of the host rocks. Based on LA-ICP-MS sphene U-Pb dating, eclogite-like rocks yield a Late Jurassic age (160±19 Ma).

Thermodynamic Modeling and Sensitivity Analysis of Kd Values for Radionuclide Migration in Sedimentary Host Rocks

2003 ◽  
Vol 807 ◽  
Author(s):  
Caterina Talerico ◽  
Michael Ochs ◽  
Shinzo Ueta ◽  
Noriyuki Sasaki
Keyword(s):  
Sensitivity Analysis ◽  
Ion Exchange ◽  
Mineral Assemblage ◽  
Surface Complexation ◽  
Critical Component ◽  
Radionuclide Migration ◽  
Sorption Model ◽  
Geochemical Parameters ◽  
Kd Values ◽  
Host Rocks

ABSTRACTThe effects of key geochemical parameters on Kd values for radionuclides in the host rock (pumice, sandstone) of a LLW repository were elucidated through a sensitivity analysis, using a thermodynamic speciation/sorption model for the elements Sr and Ni. The complex mineral assemblage of the rock was approximated by a component-additivity approach. Using published ion exchange and surface complexation parameters, Kd for both Sr and Ni could be well explained by the same model mineralogy and surface chemistry. Model results suggest that pCO2 can have a significant effect on Kd, and that a correct approximation of groundwater chemistry is a critical component of sorption modeling.

An applied mineralogical investigation of concrete degradation in a major concrete road bridge

1990 ◽  
Vol 54 (377) ◽  
pp. 637-644 ◽  
Author(s):  
G. Macleod ◽  
A. J. Hall ◽  
A. E. Fallick
Keyword(s):  
Carbon Dioxide ◽  
Cement Paste ◽  
Atmospheric Carbon Dioxide ◽  
Meteoric Water ◽  
Isotope Analysis ◽  
Isotopic Fractionation ◽  
Physical Growth ◽  
Carbon Isotopic ◽  
Mineralogical Investigation ◽  
Atmospheric Carbon

AbstractA core of concrete taken from a major road bridge in the Strathclyde Region, Scotland, has been subjected to an applied mineralogical investigation, which involved stable isotope analysis, petrography, X-ray diffraction and scanning electron microscopy.The structure is actively undergoing severe degradation due to mineral growth which is related to chemical reactions between the concrete and pore fluid. The physical growth of minerals causes disfigurement and structural weakening.Pyrite and pyrrhotine hosted by dolerite aggregate appear to have been oxidized, providing sulphate for the deposition of ettringite and minor gypsum, in spheroidal cavities within the cement paste. The rainwater which passes through the structure mobilising sulphate from original gypsum in the paste and oxidizing the iron sulphides is also involved in the further leaching of elements from the cement paste and in the deposition of calcite. The isotopic values of calcites forming a crust on the concrete and a stalactite under the bridge are similar with δ13C= −19‰ PDB and δ18‰= +16‰ SMOW. We suggest that atmospheric carbon dioxide was the carbon source. The carbon isotopic fractionation of −12‰ from atmospheric carbon dioxide of δ13C= −7‰, (O'Neil and Barnes, 1971) can best be explained as due to a kinetic fractionation related to the hyper-basicity of the pore water. The equilibrium formation temperature of about 45°C calculated from the oxygen isotope values and assuming a δ18O value of meteoric water of −8‰ SMOW, is considered unreasonable. The exceptionally low δ18O values are attributed mainly to reaction kinetics and the calcite inheriting its oxygen, two-thirds from atmospheric carbon dioxide and one third from the meteoric formation water (O'Neil and Barnes, 1971). A δ18O value of atmospheric carbon dioxide of +41‰ SMOW and a δ18O value of meteoric water of −8‰ SMOW, lead to a calculated δ18O value for the calcites of +10‰ SMOW. The calcites analysed have a value of +16‰ and this may be due to partial re-equilibration towards a calculated value of +21‰ for calcite in equilibrium with the meteoric water at 20°C.

Secondary K-feldspar at the Precambrian–Paleozoic unconformity, southwestern Ontario

1995 ◽  
Vol 32 (9) ◽  
pp. 1432-1450 ◽  
Author(s):  
David A. Harper ◽  
Fred J. Longstaffe ◽  
Moire A. Wadleigh ◽  
Robert H. McNutt
Keyword(s):  
Meteoric Water ◽  
Elevated Temperatures ◽  
Sea Water ◽  
Wide Distribution ◽  
Late Ordovician ◽  
Lower Paleozoic ◽  
Brine Migration ◽  
Rock Water Interaction ◽  
Granitoid Gneisses ◽  
Host Rocks

The Precambrian–Paleozoic boundary in the subsurface of southwestern Ontario commonly is characterized by secondary K-feldspar. In the weathered and altered Precambrian granitoid gneisses at the unconformity, secondary K-feldspar has replaced preexisting minerals, and also occurs as discrete crystals of adularia, overgrowths on altered minerals, and microcrystalline veinlets. The K-feldspar is chemically pure (Or99–100) and has high δ18O values (+18.9 to +21.4‰ Vienna Standard Mean Ocean Water), features that indicate crystallization at low temperatures. Secondary K-feldspar also occurs in Cambro-Ordovician clastic and carbonate rocks that immediately overlie the Precambrian basement. K/Ar (453 ± 9 to 412 ± 8 Ma) and Rb/Sr (440 ± 50 Ma) dates obtained for secondary K-feldspar from the Precambrian host rocks suggest that its crystallization is unrelated to Precambrian weathering or early diagenesis of the immediately overlying Cambro-Ordovician strata. Estimated crystallization temperatures for the secondary K-feldspar (≥100 °C) exceed presumed burial temperatures for the Precambrian–Paleozoic boundary in southwestern Ontario during Late Ordovician–Silurian time. We infer that secondary K-feldspar formed from a hot brine that moved preferentially along the Precambrian–Paleozoic unconformity. The wide distribution of secondary K-feldspar of Late Ordovician–Silurian age throughout mid-continental North America at the Precambrian–Paleozoic boundary records the regional extent of this process. Some Cambro-Ordovician rocks elsewhere in the mid-continent also contain secondary K-feldspar and illitic clay of Late Pennsylvanian–Early Permian age, suggesting more than one episode of fluid movement. Major pulses of orogenic activity may have initiated brine migration. We speculate that the brine originated as connate (sea) water trapped in lower Paleozoic strata, and was modified by rock–water interaction at elevated temperatures, and by mixing with meteoric water.

Paleomagnetism of the Keweenawan Chipman Lake and Seabrook Lake carbonatite complexes, Ontario

1992 ◽  
Vol 29 (6) ◽  
pp. 1215-1223 ◽  
Author(s):  
D. T. A. Symons
Keyword(s):  
Magnetic Field ◽  
Remanent Magnetization ◽  
Pole Position ◽  
Alteration Zone ◽  
Contact Aureole ◽  
Isothermal Remanent Magnetization ◽  
Abitibi Subprovince ◽  
Normal Polarity ◽  
Reversed Polarity ◽  
Host Rocks

The Chipman Lake complex crops out as a series of carbonatite and related alkalic mafic dikes in the Wabigoon Subprovince of the Superior Province, whereas the Seabrook Lake complex crops out as an alkalic syenite – carbonatite stock in the Abitibi Subprovince. Paleomagnetic analysis was done on specimens from 23 and 19 sites located in and around the Chipman Lake and Seabrook Lake complexes, respectively, using detailed alternating-field and thermal step demagnetization and isothermal remanent magnetization tests. Contact tests with adjacent Archean host rocks show that both complexes retain a primary characteristic remanence (ChRM). The Chipman Lake's ChRM is retained in 11 dikes with normal polarity and one dike with reversed polarity and at one site with normal polarity and one site with reversed polarity from the fenite alteration zone. Its ChRM gives a pole position at 186°E, 38°N (dp = 7°, dm = 11°), which corresponds to a Keweenawan age of 1098 ± 10 Ma, suggesting that younger K–Ar amphibole ages do not date emplacement. The ChRM of the host rock, the Chipman Lake diorite stock, gives a pole at 49°E, 51°N (dp = 8°, dm = 13°), showing that it is not part of the Keweenawan complex but may be a 2.45 Ga Matachewan intrusive. The Seabrook Lake complex's ChRM is found at six normal polarity sites from within the complex and at four normal and three reversed polarity sites from within the fenitized Archean granite and Matachewan diabase of the contact aureole. It gives a pole position at 180°E, 46°N (dp = 11°, dm = 17°), which corresponds to a Keweenawan age of 1103 ± 10 Ma, agreeing with K/Ar biotite ages. The paleomagnetic data indicate that no significant motion on the Kapuskasing Structural Zone occurred after emplacement of the complexes excluding minor vertical uplift of less than about 4 km, and that there were multiple polarity transitions of a symmetric Earth's magnetic field during Keweenawan time.

scholarly journals Hydrotermální mineralizace s dickitem v ordovických jílovcích bohdaleckého souvrství z tunelu metra linky D v Praze na Pankráci

2020 ◽  
Vol 28 (1) ◽  
pp. 116-125
Author(s):  
Zdeněk Dolníček ◽  
Petr Stöhr ◽  
Jana Ulmanová ◽  
Luboš Vrtiška ◽  
Radana Malíková
Keyword(s):  
Mineral Assemblage ◽  
Short Hair ◽  
Lower Paleozoic ◽  
Fault Structure ◽  
Friction Heat ◽  
Prague Basin ◽  
A Value ◽  
Paleozoic Rocks ◽  
Host Rocks ◽  
Thermal Overprint

Two types of hydrothermal veins were found in the Ordovician claystones of the Bohdalec Formation (Barrandian, Prague Basin) during the excavation of tunnel of subway Line D at Prague-Pankrác site. The first type is represented by short hair-thin veinlets of various directions fulfilled by dickite. The second type comprises thicker NNW - SSE trending veins with prevailing quartz, which cut the host rocks across the whole width of the gallery. In addition to quartz, they contain also dickite, chlorite (thuringite-chamosite), carbonates of dolomite-ankerite series (Dol37.5-44.0Ank42.0-46.8Ktn10.9-16.1), calcite, fluorapatite, pyrite (with up to 0.5 wt. % Mn), galena (with ~0.6 wt. % Se) and sphalerite (with ~1 wt. % Fe and up to 0.35 wt. % Sn and 0.36 wt. % Cu). Except for calcite, which forms younger veinlets in older quartz fill, all other mentioned minerals form minute inclusions enclosed in quartz, which are arranged parallel with outer margin of the vein. Based on mineral assemblage and chemical composition of individual minerals, highly variable crystallization temperatures (<100 - 350 °C) can be interpreted in various mineralogically distinct domains of the quartz vein. We assume a polyphase, episodic origin of individual domains of the vein fill, close to the crack-seal mechanism, which was bound to successive evolution of the adjacent fault structure. The maximum formation temperatures exceeding by a value of ca. 100 °C the highest reported temperatures of Variscan thermal overprint of Lower Paleozoic rocks of the Prague Basin are explained by production of friction heat in the fault structure. It is probable that part of parent fluids originated from sedimentary iron ores occurring in the host Ordovician sedimentary sequence.

scholarly journals Fahlbands of the Keret archipelago, White Sea: the composition of rocks and minerals, ore mineralization

2020 ◽  
Vol 245 ◽  
pp. 513-521
Author(s):  
Laysan Salimgaraeva ◽  
Sergey Skublov ◽  
Aleksey Berezin ◽  
Olga Galankina
Keyword(s):  
White Sea ◽  
Mobile Belt ◽  
The White Sea ◽  
Geochemical Characteristic ◽  
Ni Content ◽  
Icp Ms ◽  
Ore Mineralization ◽  
Sulfide Content ◽  
Small Grains ◽  
Host Rocks

This paper presents a complex mineralogical and geochemical characteristic (based on SEM-EDS, ICP-MS analysis) of the fahlband rocks of the Kiv-Guba-Kartesh occurrence within the White Sea mobile belt (WSMB). The term “fahlband” first appeared in the silver mines of Kongsberg in the 17th century. Now fahlbands are interlayers or lenses with sulfide impregnation, located in the host, usually metamorphic rock. The level of sulfide content in the rock  exceed the typical accessory values, but at the same time be insufficient for massive ores. Fahlbands are weathered in a different way than the host rocks, so they are easily distinguished in outcrops due to their rusty-brown color. The studied rocks are amphibolites, differing from each other in garnet content and silicification degree. Ore mineralization is represented mainly by pyrrhotite and pyrite, and pyrrhotite grains are often replaced along the periphery by iron oxides and hydroxides, followed by pyrite overgrowth. At the same time, the rock contains practically unaltered pyrrhotite grains of irregular shape with fine exsolution structures composed of pentlandite, and individual pyrite grains with an increased Ni content (up to 5.4 wt.%). A relatively common mineral is chalcopyrite, which forms small grains, often trapped by pyrrhotite. We have also found single submicron sobolevskite and hedleyite grains. The REE composition of the fahlband rocks suggests that they are related to Archean metabasalts of the Seryakskaya and Loukhsko-Pisemskaya structures of the WSMB, rather than with metagabbroids and metaultrabasites common in the study area.

scholarly journals Constituent Mineral and Water-Soluble Components of Volcanic Ash from the 2018 Eruption of Mt. Motoshirane of Kusatsu-Shirane Volcano, Japan

2019 ◽  
Vol 14 (7) ◽  
pp. 991-995 ◽  
Author(s):  
Muga Yaguchi ◽  
Takeshi Ohba ◽  
Nozomi Numanami ◽  
Ryohei Kawaguchi ◽  
◽  
...  
Keyword(s):  
High Temperature ◽  
Liquid Phase ◽  
Mineral Assemblage ◽  
Volcanic Ash ◽  
Volcanic Edifice ◽  
Water Soluble ◽  
Alteration Zone ◽  
Basement Rocks ◽  
Acid Alteration ◽  
Soluble Components

Constituent minerals and water-soluble components of the volcanic ash discharged from the eruption of Mt. Motoshirane on January 23, 2018, were analyzed to investigate the source environment of this eruption. The ash sample included quartz, plagioclase, cristobalite, pyrite, alunite, kaolinite, and pyrophyllite; its mineral assemblage suggests that a high-temperature acid alteration zone had been formed in the volcanic edifice of Mt. Motoshirane. The presence of pyrophyllite in the ash sample indicates that the explosion of this eruption took place at a depth reaching the basement rocks of Mt. Motoshirane. Further, the adhesion amount of water-soluble components detected from the ash sample is smaller than that in the ashes from the 1982 eruption of Mt. Shirane, indicating that the ash discharge of the 2018 eruption of Mt. Motoshirane took place in a condition in which the degree of involvement of the liquid phase was relatively small.

scholarly journals Supplemental Material: Hydrogeochemical evolution of formation waters responsible for sandstone bleaching and ore mineralization in the Paradox Basin, Colorado Plateau, USA

2022 ◽  
Author(s):  
Ji-Hyun Kim ◽  
et al.
Keyword(s):  
Meteoric Water ◽  
Colorado Plateau ◽  
Brine Solution ◽  
Paradox Basin ◽  
Hydrogeochemical Evolution ◽  
Ore Mineralization

Table S1: (ST1). PHREEQC inverse mixing modeling for the Mississippian Leadville Ls brine (Solution 3) assumed to be evolved from a mixture of the meteoric water endmember (Solution 1) and evaporated paleo-seawater endmember (Solution 2); Table S2: (ST2). PHREEQC inverse mixing modeling for the salt anticline brine (Solution 3) assumed to be evolved from a mixture of the meteoric water endmember (Solution 1) and evaporated paleo-seawater endmember (Solution 2).

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