scholarly journals Geological characteristics of hydrothermal alteration zone landslides: Example from the Ikutahara-Minami landslide area, Hokkaido, Japan

2011 ◽  
Vol 48 (3) ◽  
pp. 139-146 ◽  
Author(s):  
Hiroyuki MAEDA ◽  
Hiroshi NAYA ◽  
Satoshi UEMATSU ◽  
Masanori KOHNO
Keyword(s):  
Hydrothermal Alteration ◽  
Alteration Zone ◽  
Landslide Area ◽  
Geological Characteristics

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 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.

scholarly journals Mineralogical and Geochemical Control of Altered Andesitic Tuff upon Debris Slide Occurences at Pelangan Area, Southern Mountain of Lombok Island, Indonesia

2016 ◽  
Vol 1 (1) ◽  
pp. 19 ◽  
Author(s):  
Dwi Winarti ◽  
Dwikorita Karnawati ◽  
Hary Christady Hardiyatmo ◽  
Srijono Srijono
Keyword(s):  
Clay Minerals ◽  
Clay Mineral ◽  
Hydrothermal Alteration ◽  
Gold Mineralization ◽  
Slope Instability ◽  
Landslide Area ◽  
Debris Slide ◽  
Argillic Alteration ◽  
Wet Condition ◽  
Lombok Island

Debris slides were recently found in the Pelangan area at Southern Mountain of Lombok Island, Indonesia. Pelangan is well known as the gold mineralization and hydrothermal alteration area. This study is aimed to identify the mineralogy and geochemistry of altered andesitic tuff that controlled slope instability and induced debris slides. For this purpose, it is necessary to prepare the field observation and laboratory analyses. Landslide inventory reveals that the Pelangan debris slides mostly occur in altered andesitic tuff. Based on the outcrop observations in the field, andesitic tuff found around the Pelangan debris slides have been altered in general. The strong intensity of alteration developed by hydrothermal alteration in this study area produces large amount of clay minerals especially montmorillonite, kaolinite, and illite. The abundance of those clay minerals reflect the intermediate argillic alteration. Montmorillonite is a type of clay mineral that easily swells at wet condition and easily shrinkages at dry condition. Swelling of clay mineral destroys intersheet and interlayer bonds, and reduces shear strength. The presence of clay minerals in the altered andesitic tuff of intermediate argillic zone can be considered as one of the factors that induced to the Pelangan debris slides. Further studies on geotechnical and slope stability analysis of the landslide area are crucial to be done for better understanding of the characteristics of the altered rocks inducing hazardous landslides.

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 Initial mechanism of lands-ide occurrence in hydrothermal alteration zone near MTL, Shikoku lsland, Japan

2004 ◽  
Vol 41 (2) ◽  
pp. 121-130
Author(s):  
Masaaki MIYAHARA ◽  
Ryuji KITAGAWA ◽  
Ryuichi YATABE ◽  
Kinutada YOKOTA
Keyword(s):  
Hydrothermal Alteration ◽  
Alteration Zone
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