Petrology, mineralogy, and geochemistry of sandstones of the lower Huronian Matinenda Formation: resemblance to underlying basement rocks

1993 ◽  
Vol 30 (6) ◽  
pp. 1209-1223 ◽  
Author(s):  
S. J. Sutton ◽  
J. B. Maynard
Keyword(s):  
Source Area ◽  
Mineral Chemistry ◽  
Lower Grade ◽  
Lake Area ◽  
Fine Grained ◽  
Weathered Granite ◽  
Basement Rocks ◽  
High K ◽  
Textural Data ◽  
Bulk Chemistry

Bulk chemistry, mineralogy, mineral chemistry, cathodoluminescence characteristics, and textural data are used to constrain provenance and the role of postdepositional alteration processes in sandstones of the lower Huronian Matinenda Formation. Samples studied are from the Elliot Lake – Blind River and Agnew Lake areas, which experienced subgreenschist and biotite-grade greenschist metamorphism, respectively. Both areas, but particularly the lower grade area, contain some K-rich samples, with much of the K in detrital-appearing K-feldspar. In places K-feldspar is partially replaced by potassic mica. Plagioclase (mostly albite) is rare in the Elliot Lake – Blind River samples, and only common along a few horizons in the Agnew Lake section. It is suggested that the predominance of K-feldspar over plagioclase and the high K/Na ratios indicate a K-rich source area and in particular a weathered granite source. Framework mineralogy is found to be similar to material reported from sub-Matinenda weathered granite. The abundance of fine-grained micaceous matrix within the Matinenda varies considerably among samples, and the composition of the mica varies, correlating strongly with bulk chemistry. Some matrix has clearly been generated by alteration of framework K-feldspar. Feldspar alteration may have liberated K that was carried to the underlying regolith where it was fixed by weathering-product clay minerals. Fluids involved in alteration do not appear to have pervasively affected the Matinenda in either the Elliot Lake – Blind River or the Agnew Lake area.

Electron microscope and microprobe analysis of chlorite–mica stacks in the Wenlock turbidites, mid Wales, U.K.

1986 ◽  
Vol 123 (3) ◽  
pp. 299-306 ◽  
Author(s):  
Andrew J. Dimberline
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Source Area ◽  
Pressure Solution ◽  
Pore Waters ◽  
Bulk Rock ◽  
High K ◽  
Backscattered Electron

AbstractChlorite–mica stacks in the Wenlock turbidites have been studied using backscattered electron microscopy and electron microprobe analysis, combined with thin-section work and bulk rock chemical analysis. The stacks occur in fine sandstones and silt–mud turbidites and range in length from < 30 μm to 1.5 mm. They consist of interlayered packets of Fe-rich chlorite and mica.Combined textural and chemical data suggest that many of the stacks represent altered detrital biotite micas. A four-stage alteration sequence is proposed:(1) Subaerial alteration of biotite, in the source area, to interlayered biotite–hydrobiotite/vermiculite.(2) Post-depositional collapse of vermiculite to form a mica phase under conditions of high K+/H+ in the sediment pore waters.(3) Decrease in K+/H+ ratio, possibly due to H+ build up in the fermentation zone, causing alteration of biotite layers to chlorite.(4) Kinking of the stacks and pressure solution of chlorite early in the development of cleavage.

The relationship between source supply and mixed deposition of siliciclastic and carbonate: First to second member of the Shahejie Formation, Paleogene, Bohai Sea area, China

2021 ◽  
pp. 1-28
Author(s):  
Wei Xu ◽  
Zhengyu Li ◽  
Huiyong Li ◽  
Can Zhang ◽  
Meng Zhao ◽  
...  
Keyword(s):  
Large Scale ◽  
Bohai Sea ◽  
Source Area ◽  
Carbonate Sediments ◽  
Fine Grained ◽  
Strong Source ◽  
Shahejie Formation ◽  
Mixed Sediments ◽  
Sea Area ◽  
Buried Hill

There are various types of mixed siliciclastic-carbonate sediments developed in the Bohai Sea area during the period of the first to second member of the Shahejie Formation (E2s1-2) of the Paleocene. We have concluded that the period of E2s1-2 was very suitable for the development of carbonate minerals and organisms because of the stable tectonic background, the weak siliciclastic influence of large source systems outside the basin, and the high salinity of the water. There were many local uplifts inside the basin during E2s1-2, and the source area, supply direction, and quantity of the local provenance varied greatly. We summarized that the mixed sediments generally developed in the intermittent and stagnant periods of the source supply, or on the flank or distal end of the source supply direction due to the absence of direct interference of terrigenous clasts. To a large extent, the formation of different types of mixed deposits is controlled by the different spatiotemporal relationship with siliciclastic supply. The background of strong source supply led to the formation of large-scale mixed deposits that were mainly composed of terrigenous clasts. Mixed deposits are mainly composed of organisms and carbonate with relatively large depositional thickness formed on the flank of source supply in the steep slope area. On the flank of source supply in the gentle slope belt, thinner mixed deposits with terrigenous clasts mainly formed and thin-layer carbonate clastic-dominated deposits formed on abandoned deltas. On the uplift of the buried hill far away from the provenance, thick mixed deposits mainly composed of bioclastic were formed whereas fine-grained mixed deposits formed under the low-energy argillaceous background.

scholarly journals Scaling property of ideal granitic sequences

2007 ◽  
Vol 14 (3) ◽  
pp. 237-246 ◽  
Author(s):  
D. Xu ◽  
Q. Cheng ◽  
F. Agterberg
Keyword(s):  
Lake Area ◽  
Fine Grained ◽  
Multi Scale ◽  
Invariance Properties ◽  
The Past ◽  
Ideal Granite ◽  
Markov Properties ◽  
The Ideal

Abstract. Quantification of granite textures and structures using a mathematical model for characterization of granites has been a long-term attempt of mathematical geologists over the past four decades. It is usually difficult to determine the influence of magma properties on mineral crystallization forming fined-grained granites due to its irregular and fine-grained textures. The ideal granite model was originally developed for modeling mineral sequences from first and second-order Markov properties. This paper proposes a new model for quantifying scale invariance properties of mineral clusters and voids observed within mineral sequences. Sequences of the minerals plagioclase, quartz and orthoclase observed under the microscope for 104 aplite samples collected from the Meech Lake area, Gatineau Park, Québec were used for validation of the model. The results show that the multi-scale approaches proposed in this paper may enable quantification of the nature of the randomness of mineral grain distributions. This, in turn, may be related to original properties of the magma.

The Gow Lake impact structure, northern Saskatchewan

1977 ◽  
Vol 14 (8) ◽  
pp. 1788-1795 ◽  
Author(s):  
M. D. Thomas ◽  
M. J. S. Innes
Keyword(s):  
Impact Crater ◽  
Fine Grained ◽  
Model Studies ◽  
Deformation Structures ◽  
Basement Rocks ◽  
Clear Glass ◽  
Microscopic Features ◽  
Minimum Age ◽  
Central Island ◽  
Quartz Grains

Gow Lake, in the Precambrian Shield of Saskatchewan, is circular, 4 km in diameter, and has a large central island. Granites and quartzofeldspathic gneisses are exposed around the perimeter of the lake, whereas the island is formed largely of brecciated equivalents. Most of the breccias are composed entirely of clastic material, but at one locality fine-grained felted matrices form a significant component of the breccias, and coronas of clear glass surround quartz grains. The latter breccias also contain microscopic features characteristic of shock metamorphism, among which multiple sets of planar deformation structures in quartz are particularly diagnostic. Similar shock metamorphic features have been widely reported from terrestrial meteorite craters; accordingly, Gow Lake is interpreted as a deeply eroded impact crater and the felted matrices as impact melts.A local negative gravity anomaly with an amplitude of 3 mGal centered on the lake is attributed mainly to highly fractured basement rocks underlying the lake, which model studies indicate may extend to a depth of 900 m. A provisional minimum age of 100 Ma is proposed for the crater.

Brittle–ductile fabrics and P–T conditions of deformation in the East Pernambuco shear zone (Borborema Province, NE Brazil)

2020 ◽  
Vol 178 (1) ◽  
pp. jgs2020-109
Author(s):  
Paulo Castellan ◽  
Gustavo Viegas ◽  
Frederico M. Faleiros
Keyword(s):  
Shear Zone ◽  
Microstructural Analysis ◽  
Mineral Chemistry ◽  
Prism Slip ◽  
Content Type ◽  
Fine Grained ◽  
Brittle Ductile Transition ◽  
Epma Analysis ◽  
Borborema Province ◽  
Supplementary Material

Fabrics of the East Pernambuco shear zone (EPSZ) were studied via microstructural analysis, mineral chemistry and isochemical phase diagram modelling to constrain the pressure and temperature conditions of deformation during shearing. Granitic mylonites show fractured feldspar porphyroclasts embedded in a fine-grained, recrystallized quartzo-feldspathic matrix. These mylonites grade laterally into banded ultramylonites characterized by stretched feldspar clasts alternated with recrystallized quartz bands. Fractures in these ultramylonites are filled by phyllosilicates. The mineral chemistry of the feldspars points to systematic changes between porphyroclasts, grains within fractures and fine-grained mixtures. Quartz crystallographic fabrics in the mylonites suggest activation of prism slip, while the ultramylonites show the activation of both rhomb and basal slip systems. Thermodynamic modelling suggests that the mylonites were formed at 4.75 ± 0.25 kbar and 526 ± 9°C, while the ultramylonites yield conditions of 5.9 ± 1 kbar and 437 ± 17°C. These observations suggest that the EPSZ records a heterogeneous path of strain accommodation, marked by decreasing temperature from its western sector to its eastern termination. The differences in metamorphic conditions are consistent with a transitional, brittle–ductile strain regime. Such characteristics indicate that the EPSZ is a Neoproterozoic shear belt nucleated and heterogeneously exhumed at the brittle–ductile transition, possibly in an intracontinental setting.Supplementary Material: EPMA analysis of feldspars in Caruaru and Gravatá domains and T-X(O2) pseudosections are available at https://doi.org/10.6084/m9.figshare.c.5125957

scholarly journals Mineral chemistry and formation conditions of calc-silicate minerals of Qozlou Fe skarn deposit, Zanjan Province, NW Iran

2019 ◽  
Vol 12 (21) ◽  
Author(s):  
Mir Ali Asghar Mokhtari ◽  
Hossein Kouhestani ◽  
Kazem Gholizadeh
Keyword(s):  
Mineral Chemistry ◽  
Skarn Deposit ◽  
Silicate Minerals ◽  
Porphyritic Granite ◽  
Nw Iran ◽  
High K ◽  
Ore Minerals ◽  
Mineralized Zone ◽  
Supergene Processes ◽  
Carbonaceous Rocks

Abstract The Qozlou Fe skarn deposit is located at the Abhar–Mahneshan belt of the Central Iranian Zone. It is associated with Upper Eocene porphyritic granite that intruded into the Upper Cretaceous impure carbonaceous rocks. The Qozlou granite has high-K calc-alkaline affinity and is classified as subduction-related metaluminous I-type granitoids. Skarn aureole in the Qozlou is composed of endoskarn and exoskarn zones, with the exoskarn zone being the main skarn and mineralized zone. It includes garnet skarn, garnet-pyroxene skarn, pyroxene skarn, epidote skarn, and pyroxene-bearing marble sub-zones. The Qozlou Fe deposit is 300 m long and 5–30 m wide. Magnetite is the main ore mineral associated to pyrite, chalcopyrite, and pyrrhotite. Garnet, clinopyroxene, actinolite, epidote, calcite, and quartz occur as gangue minerals. Covellite, hematite, and goethite were formed during the supergene processes. The ore and gangue minerals have massive, banded, disseminated, brecciated, vein–veinlets, replacement, and relict textures. EPMA data indicate that garnets have andradite–grossularite compositions (Ad39.97–100–Gr0–49.62) and clinopyroxenes have diopsidic composition (En29.43–42.5–Fs14.31–20.99–Wo43.08–50.17). Based on mineralogical and textural criteria, skarnification processes in the Qozlou skarn can be categorized into three discrete stages: (1) isochemical (metamorphic–bimetasomatic), (2) metasomatic prograde, and (3) metasomatic retrograde. Anhydrous calc-silicate minerals (garnet and clinopyroxene) were formed during the prograde metasomatic stage, while ore minerals and hydrous calc-silicate minerals were formed during the retrograde ore-forming sub-stage. Temperature and ƒO2 conditions range between 430 and 550 °C and 10−26 and 10−23, respectively, for the metasomatic prograde stage. The retrograde metasomatizing fluids had likely ƒS2 = 10−6.5 and temperatures < 430 °C at the beginning of the ore-forming sub-stage.

Petrology of the Gillis Mountain pluton, Cape Breton Island, Nova Scotia

1981 ◽  
Vol 18 (2) ◽  
pp. 395-404 ◽  
Author(s):  
S. M. Barr ◽  
A. M. O'Beirne
Keyword(s):  
Hydrothermal Activity ◽  
Parent Magma ◽  
Metallic Elements ◽  
Cape Breton Island ◽  
Porphyritic Granite ◽  
Fine Grained ◽  
Cape Breton ◽  
Mineralization Processes ◽  
Devonian Age ◽  
Bulk Chemistry

The Gillis Mountain pluton is a small composite granitoid intrusion in southeastern Cape Breton Island. It is one of the few plutons of known Devonian age in Cape Breton Island and is particularly significant because of the presence of Cu–Mo mineralization with porphyry affinities. The pluton consists of three main phases (quartz monzodiorite, porphyritic granite, and fine-grained granite) with minor late dykes of granite, granitic porphyry, and aplite. These phases probably represent a differentiation sequence from an 'I-type' parent magma of calc-alkalic affinity. All phases have been affected by phyllic and possibly potassic alteration, presumably related to the mineralization processes. However, this hydrothermal activity appears to be little reflected in the bulk chemistry of the pluton, except possibly in increased barium content and large standard deviations in the metallic elements and sulphur.

Paleogeography of the Matapédia basin in the Gaspé Appalachians: initiation of the Gaspé Belt successor basin

2004 ◽  
Vol 41 (5) ◽  
pp. 553-570 ◽  
Author(s):  
Michel Malo
Keyword(s):  
Carbonate Platform ◽  
Source Area ◽  
Turbidity Currents ◽  
Northern Limit ◽  
Fine Grained ◽  
The North ◽  
Iapetus Ocean ◽  
Thrust Sheets ◽  
Siliciclastic Rocks ◽  
Lime Muds

The Matapédia basin consists of the uppermost Ordovician – lowermost Silurian deep-water, fine-grained carbonate–siliciclastic rocks of the Honorat (Garin Formation) and Matapédia groups (Pabos and White Head formations), the lower rock assemblage of the Gaspé Belt in the Gaspé Appalachians. Paleogeographic maps of eight time slices from the Caradocian to the Llandoverian are presented to better understand the tectonosedimentary evolution of the Matapédia basin. Deposition evolved from siliciclastic (Garin Fm.) to argillaceous limestones (Pabos Fm.), to limestones (White Head Fm.). The overall change from terrigenous (Garin Fm.) to limestone facies (White Head Fm.) reflects a change in the source area. Paleocurrent directions and composition of sandstones indicate an orogenic source area to the south for the Garin Formation, which is believed to be the inliers of the Humber and Dunnage zones in the southern Gaspé and New Brunswick Appalachians. Lime muds deposited by turbidity currents coming from the north suggest the Anticosti active carbonate platform as the source area for the White Head Formation. The Matapédia basin was filled from south to north. First deposits, the Garin Formation, occurred south of the Taconian thrust sheets (Humber Zone) and also south of the Grenville basement. This region was the domain of the Ordovician Iapetus Ocean (Dunnage Zone). The northern limit of the basin migrated northward during deposition of the Matapédia Group in Ashgillian–Llandoverian times and reached its actual northern limit at the very end of the Llandoverian (C6), when siliciclastic facies of the lower Chaleurs Group were deposited.

Study on Phosphorus Distribution from Sediment of Different Trophic Area of Taihu Lake and its Temporal Changes

2013 ◽  
Vol 295-298 ◽  
pp. 1663-1666
Author(s):  
Jian Hang Qu ◽  
Xiao Bing He ◽  
Hai Feng Li ◽  
Huan Chen Zhai ◽  
Yuan Sen Hu
Keyword(s):  
Taihu Lake ◽  
Algal Growth ◽  
Eutrophic Lake ◽  
Temporal Changes ◽  
Phosphorus Concentration ◽  
Lower Grade ◽  
Lake Area ◽  
Overlying Water ◽  
Phosphorus Forms ◽  
Water Eutrophication

Phosphorus is the key restraining factor for algal growth and water eutrophication, which is a global problem of environmental pollution. Using a sequential phosphorus extraction method, the phosphorus forms in sediment and their distribution from different trophic area of Taihu Lake (China) and their temporal changes were studied. Results showed that, concentration of Fe-P in sediment was the highest and successively Al-P, which was much higher than that of Ca2-P, Ca10-P, Ca8-P and O-P. All the phosphorus forms were more abundant in sediment 16# of eutrophic lake area, higher than that of moderate eutrophic and the lower-grade trophic area, with the last as relatively the lowest. Phosphorus concentration in June and September was much higher than that of March. Phosphorus in sediment of Taihu Lake had great releasing potential to the overlying water.

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