Oxygen, carbon and strontium isotope study of the carbonatitic dolomite host of the Bayan Obo Fe-Nb-REE deposit, Inner Mongolia, N China

1997 ◽  
Vol 61 (407) ◽  
pp. 531-541 ◽  
Author(s):  
M. J. Le Bas ◽  
B. Spiro ◽  
Yang Xueming
Keyword(s):  
Sedimentary Rocks ◽  
Coarse Grained ◽  
Trace Element Geochemistry ◽  
Element Geochemistry ◽  
Fine Grained ◽  
Dolomite Marble ◽  
Ore Body ◽  
Ore Bodies ◽  
Isotope Study ◽  
Bayan Obo

AbstractThe large Fe-Nb-REE deposit at Bayan Obo is hosted by a dolomite marble within the thrust complex of marbles, quartzites and slates that belongs to the Bayan Obo Formation of mid-Proterozoic age. The dolomite is either a dolomitized sedimentary limestone subsequently mineralized and tectonically thrust and folded, or a dolomite (or dolomitized) carbonatite intrusion with late-stage recrystallization and mineralization that has been subsequently tectonically deformed.O and C isotope data indicate that the sedimentary limestones and dolomites of the Bayan Obo Formation, which occur in the thrust stack together with quartzites and slates, have values of δO c. +20 per mil (SMOW) and δC c. zero. In contrast, the coarser grained facies of the large (0.5 × 10 km) dolomite marble which hosts the REE ore body has δO per mil values between +8 and +12 and δC values between −5 and −3, whereas the finer-grained recrystallized and REE-mineralized dolomite marble which occurs close to the ore bodies has δO between +12 to +16 and δC between −4 and zero. 87Sr/86Sr data confirm this distinction: >0.710 for the sedimentary rocks and <0.704 for the coarse- and fine-grained dolomite marbles.These data are taken to indicate that the large and coarse-grained dolomite was an igneous carbonatite (as borne out by its fenitic contact rocks and trace element geochemistry), and that the finer grained dolomite recrystallized under the influence of mineralizing solutions which entrained groundwater. The stratiform features in the coarse-grained dolomite that are evident in the field are interpreted as tectonic layering.

Mineralogy, geochemistry and petrogenesis of the V-Ti-bearing and chromiferous magnetite deposits hosted by Neoarchaean Channagiri Mafic-Ultramafic Complex, Western Dharwar Craton, India: Implications for emplacement in differentiated pulses

2014 ◽  
Vol 6 (4) ◽  
Author(s):  
Tadasore Devaraju ◽  
Kallada Jayaraj ◽  
Thavaraghatta Sudhakara ◽  
Tuomo Alapieti ◽  
Beate Spiering ◽  
...  
Keyword(s):  
Dharwar Craton ◽  
Coarse Grained ◽  
Trace Element Geochemistry ◽  
Second Phase ◽  
Element Geochemistry ◽  
Silicate Mineral ◽  
Interface Zone ◽  
Fine Grained ◽  
Ultramafic Complex ◽  
Late Stages

AbstractThe Channagiri Mafic-Ultramafic Complex occupies lowermost section of the Neoarchaean Shimoga supracrustal group in the Western Dharwar Craton. It is a segmented body occupying the interdomal troughs of granitoids. The magnetite deposits occur in the northeastern portion; typically occupying the interface zone between gabbro and anorthositic. Mineralogically, the deposits are simple with abundant magnetite and ilmenite. Hogbomite is a consistent minor mineral. Magnetites are typically vanadiferous (0.7–1.25% V2O5). Ilmenite consistently analyses more MgO and MnO than coexisting magnetite. Chlorite, almost the only silicate present; lies in the range of ripidolite, corundophilite and sheridanite. The chromiferous suit occupying eastern side of Hanumalapur block (HPB) contains Fe-Cr-oxide analysing 37.8–11.9% Cr2O3 and 40.5–80% FeOt. In these too, chlorite, typically chromiferous (0.6–1.2% Cr2O3), is the most dominant silicate mineral. Geochemistry of V-Ti-magnetite is dominated by Fe, Ti and V with Al, Si, Mg and Mn contributing most of the remaining. Cr, Ni, Zn, Co, Cu, Ga and Sc dominate trace element geochemistry. The Cr-magnetite is high in Cr2O3 and PGE. Two separate cycles of mafic magmatism are distinguished in the CMUC. The first phase of first cycle, viz., melagabbro-gabbro, emplaced in the southeastern portion, is devoid of magnetite deposits. The second phase, an evolved ferrogabbroic magma emplaced in differentiated pulses, occupying northeastern portion of the complex, consists of melagabbro→gabbro-anorthosite→V-Ti magnetite→ferrogabbro sequence. Increase in oxygen fugacity facilitated deposition of V-Ti magnetite from ferrogabbroic magma pulse emplaced in late stages. The second cycle of chromiferous PGE mineralized suite comprises fine-grained ultramafite→alternation of pyroxinite-picrite→Crmagnetite sequence formed from fractionation of ferropicritic magma. HPB also includes >65m thick sill-like dioritic phase at the base of the ferriferous suit and a sinuous band of coarse-grained ultramafite enclosed within the chromiferous suit; both unrelated to the two mafic magmatic cycles.

scholarly journals Dominant Weathering Profile Assessment of Kebo-Butak Volcanic Rocks in Gedangsari and Ngawen area, Yogyakarta, Indonesia

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Fathan Hanifi Mada Mahendra ◽  
I Gde Budi Indrawan ◽  
Sugeng Sapto Surjono
Keyword(s):  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Coarse Grained ◽  
Residual Soil ◽  
Geological Condition ◽  
Weathering Profile ◽  
Fine Grained ◽  
Degree Pattern ◽  
Weathering Degree ◽  
East West

The Gedangsari and Ngawen area is predominantly composed of volcanic and volcaniclastic sequencesdistributed east – west direction of the northern parts of Southern Mountain. The massive tectonism as well as tropical climatein this region have been producing weathering profiles in varying thickness which inevitably affects thegeotechnical properties. This study aims to assess the dominant weathering profileof the lower part of Kebo-Butak Formation as well as evaluating the distribution of the discontinuity. In order to know the dominant weathering profile and discontinuity evaluation, this study utilizes a total of  26 panels from five stations investigated through a geotechnical data acquisition including the geological condition, weathering zones, joint distribution, and discontinuity characteristics. The result shows four types of dominant weathering profiles in lower part of Kebo-Butak Formation called as dominant weathering profile A, B, C, and D. Profile A, B, C consisted of a relatively identical weathering degree pattern of fresh, slightly, moderately, completely weathered zone with the variation of thicknesses. However, the weathering degree in profile D reached the residual soil degree controlled by more intensive joints. The fine-grained sedimentary rocks also tends to have smaller spacing, shorter persistence, and higher weathering degree of discontinuities as compared to coarse-grained sedimentary rocks.

scholarly journals Application of the Fine-Grained Soil Prospecting Method in Typical Covered Terrains of Northern China

Minerals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1383
Author(s):  
Hanliang Liu ◽  
Bimin Zhang ◽  
Xueqiu Wang ◽  
Zhixuan Han ◽  
Baoyun Zhang ◽  
...  
Keyword(s):  
Mineral Exploration ◽  
Mineral Resources ◽  
Northern China ◽  
Gobi Desert ◽  
Test Results ◽  
Fine Grained ◽  
Ore Body ◽  
Ore Bodies ◽  
Fine Grained Soil ◽  
Body Location

In recent years, mineral resources near the surface are becoming scarce, causing focused mineral exploration on concealed deposits in covered terrains. In northern China, covered terrains are widespread and conceal bedrock sequences and mineralization. These represent geochemical challenges for mineral exploration in China. As a deep-penetrating geochemical technology that can reflect the information of deep anomalies, the fine-grained soil prospecting method has achieved ideal test results in arid Gobi Desert covered terrain, semi-arid grassland covered terrain, and alluvium soil covered terrain of northern China. The anomaly range indicated by the fine-grained soil prospecting method is very good with the known ore body location. The corresponding relationship can effectively indicate deep ore bodies and delineate anomalies in unknown areas. Overall, the fine-grained soil prospecting method can be applied to geochemical prospecting and exploration in covered terrains.

Pb–Zn occurrences and their Pb-isotopic signatures bearing on metallogeny and mineral exploration—Paleozoic sedimentary rocks, northern Appalachians, Quebec

1988 ◽  
Vol 25 (11) ◽  
pp. 1777-1790 ◽  
Author(s):  
K. Schrijver ◽  
E. Marcoux ◽  
G. Beaudoin ◽  
J. Y. Calvez
Keyword(s):  
Continental Crust ◽  
Mineral Exploration ◽  
Sedimentary Rocks ◽  
Isotope Ratios ◽  
Isotopic Signature ◽  
Coarse Grained ◽  
Pb Isotope ◽  
Isotopic Signatures ◽  
Fine Grained ◽  
Quartz Veins

Galena Pb-isotope ratios of epithermal vein and disseminated sulfide occurrences in the Taconian Orogen and Siluro-Devonian basin cluster around 17.90–18.05 for 206Pb/204Pb and 37.70–38.00 for 208Pb/204Pb. The major source of Pb in most, if not all, occurrences is a fairly common continental crust, a characteristic found in published analyses of Grenville feldspar Pb. A southwest to northeast increase in galena 206Pb/204Pb ratios is ascribed to the supply of several types of detritus from Grenville basement during the Cambro-Ordovician: coarse-grained, K-feldspar-bearing in the southwest, grading into fine-grained phyllitic, and relatively more highly radiogenic in the northeast.Emplacement (i) of Pb–Zn–barite veins and disseminations, commonly of homogeneous crustal Pb-isotopic signature, was late Taconian; (ii) of Pb–Zn–quartz veins, of less homogeneous signature, was post-Taconian; and (iii) of Pb–Zn–carbonate veins, relatively highly radiogenic and commonly homogeneous, was late or post-Acadian. Signatures of the first-mentioned group seem to be most useful in exploration.

scholarly journals Siliciclastic sedimentation in the interlude between two Neoproterozoic glaciations, Mirbat area, southern Oman: A missing link in the Huqf Supergroup?

GeoArabia ◽  
2008 ◽  
Vol 13 (4) ◽  
pp. 45-72
Author(s):  
Ruben Rieu ◽  
Philip A. Allen
Keyword(s):  
Arabian Peninsula ◽  
Sedimentary Rocks ◽  
Crystalline Basement ◽  
Coarse Grained ◽  
Shallow Marine ◽  
Fluvial Deposits ◽  
Fine Grained ◽  
Marine Deposits ◽  
Sedimentary Succession ◽  
Late Neoproterozoic

ABSTRACT The Huqf Supergroup in Oman contains an exceptionally well-preserved and complete sedimentary record of the Late Neoproterozoic era, including the oldest components in some of Oman’s hydrocarbon plays. Outcrops of the Huqf Supergroup in northern and central Oman are now well-documented. However, a key succession in the Mirbat area of southern Oman, the Mirbat Group, which includes a stratigraphic interval missing elsewhere in the Arabian Peninsula, remains poorly understood. The &lt;1.5 km-thick Cryogenian (850–635 Ma) Mirbat Group comprises an essentially continuous succession of little-deformed sedimentary rocks containing two glacial intervals separated by c. 1 km of non-glacial marine deposits. The lowermost glacial interval (Ayn Formation) occupies deep paleovalleys incised into crystalline basement. The overlying Arkahawl Formation records at its base a major post-glacial transgression over the previous basin margin and a 300 to 400 m-thick turbidite complex consisting of 1 to 5 km-wide, coarse-grained depositional lobes embedded vertically and laterally in fine-grained distal turbidite fan deposits. Ayn Formation paleovalleys continued to serve as sediment transport routes for the coarse-grained turbidite complexes of Arkahawl times. The turbidite complex deposits gradationally pass up into a c. 500 m-thick unit of distal-marine mudstone and siltstone. The overlying c. 100 m-thick Marsham Formation records highstand deposition and the pulsed progradation of shallow-marine and fluvial deposits over offshore mudstone and siltstone in the approach to a second glaciation, represented by the Shareef Formation. The sedimentary succession described in this paper is believed to largely fill the stratigraphic gap present between the Ghubrah and Fiq formations in the Al Jabal al-Akhdar in northern Oman represented by an unconformity.

GEOTHERMAL SURVEYS IN SEDIMENTARY ROCKS NEAR GRANTS AND LAGUNA, NEW MEXICO

Geophysics ◽  
1965 ◽  
Vol 30 (3) ◽  
pp. 396-402
Author(s):  
P. Edward Byerly
Keyword(s):  
New Mexico ◽  
Pore Water ◽  
Water Table ◽  
Sedimentary Rocks ◽  
Uranium Ore ◽  
Ore Body ◽  
Downward Migration ◽  
Ore Bodies ◽  
Oxygenated Water ◽  
Drill Holes

Data obtained from temperature surveys in drill holes over two uranium ore bodies are presented as maps of isotherms at depths of 100 ft or more. Temperature surveys in permeable ore bodies above the water table may reveal zones of downward migration of oxygenated water, or zones with a comparatively large retention of pore water. These zones may be associated with an increased amount of oxidation in an ore body which is not completely oxidized.

The use of magnetic susceptibility and trace element geochemistry for the correlation of fine-grained siliciclastic sequences: a Late Llandovery example from northwest England

1999 ◽  
Vol 136 (4) ◽  
pp. 423-436 ◽  
Author(s):  
L. T. P. ENGLISH
Keyword(s):  
Magnetic Susceptibility ◽  
Bottom Water ◽  
Sediment Accumulation ◽  
Clay Mineralogy ◽  
Manganese Carbonate ◽  
Trace Element Geochemistry ◽  
Accumulation Rates ◽  
Element Geochemistry ◽  
Fine Grained ◽  
Water Oxygen

High-resolution lithological and magnetic susceptibility logs were made of two sections of the Upper Llandovery Browgill Formation in northwest England: Stockdale Beck, the type section of the Browgill Formation, and Spengill. The Browgill Formation is composed of fine-grained deep marine siliciclastics, which can be divided broadly into two facies: a homogeneous grey mudstone, deposited under oxygenated bottom-water conditions, and subordinate beds of laminated, graptolite-bearing black mudstone deposited under low bottom-water oxygen levels. The latter facies is often partially or fully diagenetically altered to chlorite nodules, occasionally with manganese carbonate nucleii. Magnetic susceptibility logs are shown to reflect variations in the illite–chlorite ratio of the clay mineralogy. Chlorite is a paramagnetic mineral, so the bands of chlorite nodules produce magnetic susceptibility highs. Correlation demonstrates that diagenetically altered beds of laminated black mudstone are continuous between the two sections, now situated 32 km apart. This lateral continuity would favour pelagic fallout in preference to gravity flow as a depositional model for both facies. A correlated sequence within the turriculatus Biozone is 3.8 times thicker at Spengill than at Stockdale Beck, probably reflecting variations in sediment accumulation rates. Correlation also identifies significant non-sequences in both sections: at least 47% of the turriculatus Biozone (including maximus Sub-biozone) is missing at Stockdale Beck and at least 77% of the crispus Biozone is missing at Spengill. The identification of non-sequences may be of value for refining graptolite biostratigraphy.

scholarly journals Kivilompolo Mo mineralization in the Peräpohja belt revisited: Trace element geochemistry and Re-Os dating of molybdenite

2020 ◽  
Vol 92 (2) ◽  
pp. 131-150
Author(s):  
Jukka-Pekka Ranta ◽  
◽  
Eero Hanski ◽  
Holly Stein ◽  
Matthew Goode ◽  
...  
Keyword(s):  
Uranium Mineralization ◽  
Coarse Grained ◽  
Geochemical Data ◽  
Trace Element Geochemistry ◽  
Element Geochemistry ◽  
Zircon Age ◽  
Porphyritic Granite ◽  
Quartz Veins ◽  
Nappe Complex ◽  
Magmatic Fluids

The Kivilompolo molybdenite occurrence is located in the northern part of the Peräpoh jabelt, within the lithodemic Ylitornio nappe complex. It is hosted within a deformed porphyritic granite belonging to the pre-orogenic 1.99 Ga Kierovaara suite. The minerali-zation occurs mostly as coarse-grained molybdenite flakes in boudinaged quartz veins, with minor chalcopyrite, pyrite, magnetite, and ilmenite. In this study, we report new geochemical data from the host-rock granite and Re-Os dating results of molybdenite from the mineralization. For the whole-rock geochemistry, the mineralized granite is similar to the Kierovaara suite granites analyzed in previous studies. Also, the ca. 2.0 Ga Re-Os age for molybdenite is equal, within error, to the U-Pb zircon age of the Kierovaara suite granite. In addition, similar molybdenite and uraninite ages have been reported from the Rompas-Rajapalot Au-Co occurrence located 30 km NE of Kivilompolo. We propose that the magmatism at around 2.0 Ga ago initiated the hydrothermal circulation that was responsible for the formation of the molybdenite mineralization at Kivilompolo and the primary uranium mineralization associated with the Rompas-Rajapalot Au-Co occurrence or at least, the magmas provided heating, and in addition potentially saline magmatic fluids and metals from a large, cooling magmatic-hydrothermal system.

Volcanic clays in the Cretaceous of southern England and Northern Ireland

Clay Minerals ◽  
1982 ◽  
Vol 17 (1) ◽  
pp. 105-156 ◽  
Author(s):  
C. V. Jeans ◽  
R. J. Merriman ◽  
J. G. Mitchell ◽  
D. J. Bland
Keyword(s):  
Northern Ireland ◽  
Western Europe ◽  
Upper Cretaceous ◽  
Isotope Analysis ◽  
Trace Element Geochemistry ◽  
Element Geochemistry ◽  
Southern England ◽  
Fine Grained ◽  
The North ◽  
The North Sea

AbstractThe mineralogy, petrology and trace element geochemistry of volcanogenic glauconites and smectite-rich clays are described and related to clay assemblages in Lower and Upper Cretaceous sediments of southern England and Northern Ireland. Volcanogenic glauconite grains represent argillized lava particles of predominantly mafic composition and may have been derived from submarine basaltic magmatism; they occur in all the sediments examined (Aptian-Senonian), and are particularly abundant in the Cenomanian-Campanian Hibernian Greensand of Antrim. The smectite-rich clays in southern England have developed by the argillization of predominantly acid or alkaline ash during early diagenesis. Three types of volcanogenic deposit are recognized. Primary bentonites are thin ash-falls deposited in quiet, brackish and marine waters (Speeton Clay, Ryazanian; Weald Clay, Barremian). Secondary bentonites are local accumulations of ash transported into the Cretaceous seas by rivers draining ash-blanketed, local land areas (London Platform, Portsdown Axis). These deposits are well-developed in the Sandgate Beds, Folkestone Beds and their contiguous deposits, and the lower part of the Gault (Upper Aptian-Middle Albian). The ash originated from penecontemporaneous, subaerial vulcanism located in the southern part of the North Sea. The most conspicuous phase of activity occurred during late Aptian times and has been dated by 40Ar/39Ar isotope analysis at 112 m.y. Bentonitic clays and marls are widespread accumulations of argillized ash that occur as a fine-grained fringing facies to glauconitic quartz sand facies. They make up the upper part of the Atherfleld Clay (Aptian) and the upper part of the Gault (Upper Albian), and they are associated respectively with the Hythe Beds (Aptian) and the Upper Greensand (Upper Albian). They may also occur in the lower part of the Lower Chalk (Cenomanian). The distribution pattern of these smectite-rich clays in southern England is related to the changing palaeogeography of the area in Cretaceous times, and the general coincidence of extensive glaueonite deposits and smectite-rich clays in the Middle and Upper Cretaceous of western Europe and along the eastern seaboard of North America is briefly discussed.

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