Detection of slip surface in earth slide based on mineral assemblages -An example of hydrothermal alteration zone landslide in East Hokkaido Japan-

2014 ◽  
Vol 51 (3) ◽  
pp. 106-112
Author(s):  
Hiroyuki MAEDA ◽  
Masanori KOHNO ◽  
Yoshihiko SEKISHITA ◽  
Satoshi UEMATSU ◽  
Hiroshi NAYA
Keyword(s):  
Hydrothermal Alteration ◽  
Slip Surface ◽  
Alteration Zone ◽  
Mineral Assemblages

ANALYSIS OF AIRBORNE SPECTRORADIOMETRIC DATA AND THE USE OF LANDSAT DATA FOR MAPPING HYDROTHERMAL ALTERATION

Geophysics ◽  
1978 ◽  
Vol 43 (5) ◽  
pp. 967-987 ◽  
Author(s):  
William Collins
Keyword(s):  
Hydrothermal Alteration ◽  
Spectral Resolution ◽  
Spectral Properties ◽  
Ferric Iron ◽  
Correlated Data ◽  
High Spectral Resolution ◽  
Alteration Zone ◽  
Landsat Data ◽  
Spectral Contrast ◽  
Aircraft Data

An airborne spectroradiometer system has been developed to take 500 channel ground target measurements simultaneously in the spectral region between 400 and 1100 nm. Survey flights with the instrument over an exposed hydrothermal alteration zone in Goldfield, Nevada provide the high‐spectral resolution and spatially correlated data necessary to establish a computerized technique for spectral discrimination of limonitic zones that could indicate mineralization. The data generated by the airborne system are used, in particular, to determine the spectral properties of alteration materials as they appear in integrated measurements over extended field areas, to determine which spectral properties are unique under field conditions and will remain unique in the low‐spectral resolution Landsat data, and to determine accurately the nature and magnitude of the relative spectral differences among geologic targets under the broadband configuration. Field measurements from the aircraft are spatially integrated over contiguous 18 m square fields‐of‐view along traverses flown to cover both background and altered rock assemblages. A small spectral signal unique to zones enriched in ferric iron minerals is recoverable in the aircraft data. Based on a differential spectral discriminant, a computer‐compatible method has been devised to extract the ferric iron signal from atmospheric and background terrain and geologically induced variations in Landsat data. The discrimination technique, adapted to satellite spectral data, was applied to the Goldfield region, including the area of known alteration and metallic mineralization. Field reconnaissance and comparison with published maps for this region has affirmed that limonitic alteration is reliably delineated by the computer analysis technique. Assessment of current satellite instrumentation based on the aircraft data analysis indicates that inclusion of more appropriate band‐pass regions in future sensors could increase spectral contrast among geologic targets by 100 percent. Reducing the field‐of‐view can also increase spectral contrast, and can help reduce spectral ambiguities among extended targets.

scholarly journals Rhenium - rich molybdenites in Thracian porphyry Mo±Cu occurrences, NE - Greece

2001 ◽  
Vol 34 (3) ◽  
pp. 1015 ◽  
Author(s):  
Β. ΜΕΛΦΟΣ ◽  
Π. ΒΟΥΔΟΥΡΗΣ ◽  
Κ. ΑΡΙΚΑΣ ◽  
Μ. ΒΑΒΕΛΙΔΗΣ
Keyword(s):  
Chemical Composition ◽  
Hydrothermal Alteration ◽  
Fluid Inclusions ◽  
Mineral Chemistry ◽  
Rare Element ◽  
Alteration Zones ◽  
Porphyry Cu ◽  
Mineral Assemblages ◽  
Host Rocks

The present study correlates both the mineralogy of the hydrothermal alteration and the mineral chemistry of molybdenites from three porphyry Mo ± Cu occurrences in Thrace: Melitena, Pagoni Rachi/Kirki and Ktismata/ Maronia. The mineralisations are genetically related to calcalkaline, subvolcanic bodies of Tertiary age. According to their mineralogical and chemical composition the host rocks are characterized as dacite (Melitena), dacitic andésite (Pagoni Rachi) and porphyry microgranite (Ktismata/Maronia). The molybdenites occur in disseminated form, as fracture fillings, as well within quartz stockworks crosscuting the central alteration zones of the intrusives. They are accompanied by the following mineral assemblages: quartz, sericite, pyrophyllite, diaspore, Ca-Ba-rich alunite, pyrite (Melitena); quartz, albite/K-feldspar, biotite, actinolite, magnetite (Pagoni Rachi); and sericite, kaolinite, pyrophyllite, chlorite (Ktismata). Preliminary microthermometric results showed homogenisation temperatures from 352° to 390 °C for Pagoni Rachi area and from 295° to 363 °C for Melitena area. The salinities range between 4.5 and 6.1 wt% eq. NaCl and between 2.7 and 3.4 wt% eq. NaCl, respectively. Detailed study on over 400 fluid inclusions from the porphyry Cu-Mo deposit in Maronia area revealed formation temperatures from 300° to 420 °C, whereas salinities are distincted in two different groups from 6 to 16 wt% eq. NaCl and from 28 to 55 wt% eq. NaCl. The chemical composition of the molybdenites from the three porphyry Mo±Cu deposits in Thrace was studied with 155 microprobe analyses. The results revealed unusual high and variable Re concentrations in the studied molybdenites. Re content in molybdenite from Melitena area vary from 0.21 to 1.74 wt%, 0.79 wt% on average. The highest values were measured in samples from Pagoni Rachi (0.45-4.21 wt%, 1.98 wt% on average). Finally, microprobe analyses from molybdenite in Ktismata/Maronia showed Re content between 0.12 and 2.88 wt% (0.76 wt% on average). Rhenium is a very rare element with many definite uses, and is mainly associated with molybdenite in porphyry type deposits. According to the data published so far the Re content in molybdenite reaches up to 0.42 wt%. It is obvious therefore that such high Re concentrations (0.12 to 4.22 wt%) from the studied molybdenites in Thrace, are very ineresting for a possible future exploitation.

scholarly journals HYDROTHERMAL ALTERATION AND VEIN TYPES OF THE RANDU KUNING PORPHYRY Cu-Au DEPOSIT AT SELOGIRI AREA, WONOGIRI

2014 ◽  
Vol 9 (1) ◽  
pp. 48-61
Author(s):  
Sutarto Sutarto ◽  
Arifudin Idrus ◽  
Sapto Putranto ◽  
Agung Harjoko ◽  
Lucas D Setijadji ◽  
...  
Keyword(s):  
Hydrothermal Alteration ◽  
Fault Zones ◽  
Alteration Zone ◽  
Quartz Veins ◽  
Porphyry Cu ◽  
Centre Line ◽  
Argillic Alteration ◽  
Intrusive Rocks ◽  
Hydrothermal Alteration Zones ◽  
Alteration Pattern

Many Tertiary hydrothermal altered dioritic composition intrusive rocks were found at the Randu Kuning area and its vicinity, Selogiri, including hornblende microdiorite, hornblende-pyroxene diorite and quartz diorite. The hydrothermal fluids which responsible for the alteration and mineralization at the area is associated with the occurence of the horblende microdiorite intrusion. The alteration zone at the Randu Kuning area and its vicinity can be divided intoseveral hydrothermal alteration zones, such as potassic (magnetite-biotite-K feldspar), prophyllitic (chlorite-magnetite-epidote-carbonate), phyllic (quartz-sericite-chlorite) and argillic (clay mineral-sericite). The alteration pattern in the Randu Kuning porphyry Cu-Au deposit is tipically a diorite model characterising by the domination of potassic alteration and prophyllitic zone. Phyllic and argillic alteration types are restrictive found within the fault zones. A lot of porphyry vein types were found and observed at the Randu Kuning area, and classified into at least seven vein types. The paragenetic sequence of those veins from theearliest to the latest respectively are 1). Magnetite-chalcopyrite±quartz-biotite veinlets, 2). Quartz±magnetite (A type) veins, 3). Banded/Laminated quartz-magnetite (M type) veins, 4). Quartz±K feldspar (B type)veins, 5). Quartz with thin centre line sulphide (AB type) veins, 6). Pyrite±chalcopyrite (C type) veinlets, and 7). Pyrite-quartz+chalcopyrire+carbonate (D type) veins. Gold and copper mineralisation of the Randu Kuning Porphyry Cu-Au deposit, mostly related to the presence of quartz veins/veinlets containing sulfide i.e. Quartz with thin centre line sulphide veins, Pyrite±chalcopyrite veinlets, and Pyrite-quartz+chalcopyrire+carbonate veins.

Hydrothermal Alteration Mineralogy and Geochemistry of the Archean World-Class Canadian Malartic Disseminated-Stockwork Gold Deposit, Southern Abitibi Greenstone Belt, Quebec, Canada

2019 ◽  
Vol 114 (6) ◽  
pp. 1057-1094 ◽  
Author(s):  
Stéphane De Souza ◽  
Benoît Dubé ◽  
Patrick Mercier-Langevin ◽  
Vicki McNicoll ◽  
Céline Dupuis ◽  
...  
Keyword(s):  
Gold Deposit ◽  
Fault Zone ◽  
Hydrothermal Alteration ◽  
Greenstone Belt ◽  
Gold Mineralization ◽  
Amphibolite Facies ◽  
Alteration Zone ◽  
Gold Deposition ◽  
Abitibi Greenstone Belt ◽  
World Class

Abstract The Canadian Malartic stockwork-disseminated gold deposit is an Archean world-class deposit located in the southern Abitibi greenstone belt. It contains over 332.8 tonnes (t; 10.7 Moz) of Au at a grade of 0.97 ppm, in addition to 160 t (5.14 Moz) of past production (1935–1981). Although the deposit is partly situated within the Larder Lake-Cadillac fault zone, most of the ore occurs up to ~1.5 km to the south of the fault zone. The main hosts of the mineralized zones are greenschist facies turbiditic graywacke and mudstone of the Pontiac Group (~2685–2682 Ma) and predominantly subalkaline ~2678 Ma porphyritic quartz monzodiorite and granodiorite. These intrusions were emplaced during an episode of clastic sedimentation and alkaline to subalkaline magmatism known as the Timiskaming assemblage (<2680–2670 Ma in the southern Abitibi). The orebodies define two main mineralized trends, which are oriented subparallel to the NW-striking S2 cleavage and the E-striking, S-dipping Sladen fault zone. This syn- to post-D2 ductile-brittle to brittle Sladen fault zone is mineralized for more than 3 km along strike. The ore mainly consists of disseminated pyrite in stockworks and replacement zones, with subordinate auriferous quartz veins and breccia. Gold is associated with pyrite and traces of tellurides defining an Au-Te-W ± Ag-Bi-Mo-Pb signature. The orebodies are zoned outward, and most of the higher-grade (>1 ppm Au) ore was deposited as a result of iron sulfidation from silicates and oxides and Na-K metasomatism in carbonatized rocks. The alteration footprint comprises a proximal alteration envelope (K- or Na-feldspar-dolomite-calcite-pyrite ± phlogopite). This proximal alteration zone transitions to an outer shell of altered rocks (biotite-calcite-phengitic white mica), which hosts sub-ppm gold grades and reflects decreasing carbonatization, sulfidation, and aNa+/aH+ or aK+/aH+ of the ore fluid. Gold mineralization, with an inferred age of ~2664 Ma (Re-Os molybdenite), was contemporaneous with syn- to late-D2 peak metamorphism in the Pontiac Group; it postdates sedimentation of the Timiskaming assemblage along the Larder Lake-Cadillac fault zone (~2680–2669 Ma) and crystallization of the quartz monzodiorite. These chronological relationships agree with a model of CO2-rich auriferous fluid generation in amphibolite facies rocks of the Pontiac Group and gold deposition in syn- to late-D2 structures in the upper greenschist to amphibolite facies. The variable geometry, rheology, and composition of the various intrusive and sedimentary rocks have provided strain heterogeneities and chemical gradients for the formation of structural and chemical traps that host the gold. The Canadian Malartic deposit corresponds to a mesozonal stockwork-disseminated replacement-type deposit formed within an orogenic setting. The predominance of disseminated replacement ore over fault-fill and extensional quartz-carbonate vein systems suggests that the mineralized fracture networks remained relatively permeable and that fluids circulated at a near-constant hydraulic gradient during the main phase of auriferous hydrothermal alteration.

Galapagos hydrothermal alteration zone found

Eos ◽  
1986 ◽  
Vol 67 (22) ◽  
pp. 497
Author(s):  
Robert W. Embley
Keyword(s):  
Hydrothermal Alteration ◽  
Alteration Zone

scholarly journals Ta-Nb mineralization in rare-metal pegmatite from north-western frame of Lypniazhka granite-migmatite structure

2020 ◽  
Vol 41 ◽  
pp. 32-41
Author(s):  
S.I. Kurуlo ◽  
◽  
N.M. Lуzhachenko ◽  
S.M. Bondarenko ◽  
V.O. Syomka ◽  
...  
Keyword(s):  
Hydrothermal Alteration ◽  
Hydrothermal Fluid ◽  
Rare Metal ◽  
Mineral Assemblages ◽  
Lower Volume ◽  
Alkaline Feldspar ◽  
First Time ◽  
North Western ◽  
Rare Metal Pegmatite ◽  
Oscillatory Zonality

The three type of rare-metal pegmatites are know in Stankuvatske ore field (Ingul megablock, the Ukraianian Shield), such as: Li-bearing, Bi-As-U and Ta-Nb pegmatites. For the first time Ta-Nb mineralisation from Ta-Nb bearing albite-K-Feldspar rare metal pegmatite have been described. Investigated pegmatite is located on the Norh-West frame of the Lypnazky granitemigmatite massive among hosted amphibolites. Rare-metal pegmatite doesn’t have obvious zonality and consist of alkaline feldspar, biotite, muscovite, dark to black colour quartz, blue-greenish apatite, nigerite, gachnite, tourmaline, monazite. The primary ferrocolumbite and Nb-rutile-II have undergone strong hydrothermal alteration. Thus primary rutile-II decomposed with formation of skeletal intergrowths of secondary cassiterite and rutile-III with a much lower volume of Nb and Ta under the influence of hydrothermal fluid. Primary homogenous Nb-rutile-I (Nb2O5+Ta2O5 from 33,5 to 42,9 wt.%) exsolved a fine trellis-like pattern and lamellar of Nb-pure rutile-III, cassiterite and Mn-rich ilmenite. The Nb-rutile-II is occurred in tabular grains with unclear internal zonation. Primary ferrcolumbite breakdown to Ti-ixiolite and Nb-rutile-III. Primary oscillatory zonality is transformed into irregularly patchy and veinlety. Recrystallized ferrotantalite is secondary and uncommon mineral. Ferrocolumbite contains 2.93 to 4.74 wt.%TiO2, and titanian ixiolite 7,33-10,76 wt.%. The (Ti,Nb)>Ta mineral assemblages, and compositional trend of columbite with very low Ta/(Ta+Nb) and Mn/ (Mn+Fe) imply a general low level of fractionation in comparison with typical beryl-columbite rare-metal pegmatites.

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