Hydrothermal alteration processes of fluorapatite and implications for REE remobilization and mineralization

2021 ◽  
Vol 176 (10) ◽  
Author(s):  
Bing Xiao ◽  
Yuanming Pan ◽  
Hao Song ◽  
Wenlei Song ◽  
Yu Zhang ◽  
...  
Keyword(s):  
Hydrothermal Alteration ◽  
Alteration Processes

scholarly journals Geology and Geothermal Setting of Tompaso Geothermal System, Indonesia, with Comparisons of Andesite Alteration Patterns with Wairakei, New Zealand

2021 ◽  
Author(s):  
◽  
Kartika Palupi Savitri
Keyword(s):  
Hydrothermal Alteration ◽  
Short Wave ◽  
Age Dating ◽  
Core Material ◽  
Geothermal System ◽  
Scattered Electron ◽  
Subsurface Geology ◽  
North Sulawesi ◽  
Alteration Processes ◽  
First Time

<p>Tompaso geothermal system is a typical volcanic arc geothermal system in North Sulawesi, Indonesia. Although situated close to the Tondano caldera, subsurface lithologies and structures do not show any evidence for caldera-related features and the system is inferred to be related to the andesitic Soputan volcano. The subsurface geology of Tompaso consists of Tuff B unit, Rhyolite unit, Andesite B unit, Pitchstone unit, Pyroclastic Breccia unit,Andesite A unit, Pumice unit, and Tuff A unit, respectively, from the oldest penetrated unit. The silicic Pitchstone and Rhyolite units are presumed to be sourced from the same magma chamber. Petrological and mineralogical observations using binocular and petrographic microscopy, short-wave infrared (SWIR) analysis, and back-scattered electron (BSE) imaging combined with energy dispersive X-ray spectroscopy (EDS) have been applied to cuttings and limited core material from three boreholes: LHD-26, LHD-27, and LHD-32. Age dating has not been undertaken and, thus, conclusions on correlations between subsurface geology inferred here with surface formation groupings from previous works cannot be drawn.  Tompaso geothermal system is characterised primarily by variations in the fracturing within the reservoir. Secondary mineralogy and the structure of present-day temperature of the system suggest that the movement of hydrothermal fluids at Tompaso is controlled by faults: the Soputan, Tempang, and A-A’ faults, the last defined for the first time in this thesis. Soputan Fault controls the outflow of the system. On the other hand, the influence of Tempang and A-A’ faults is dominant only in the upper portion of the system. The A-A’ fault likely acts as a channel for cooler meteoric surface water, while the Tempang Fault is inferred to have experienced self-sealing and appears to be an impermeable structure in the system. The self-sealing process of the Tempang Fault and/or the introduction of meteoric water through the A-A’ fault may be related to the cooling of the northern and western part of the system.  The challenges in identifying protoliths in active geothermal areas is addressed here through studies of the influence of andesite textures on the preferences of hydrothermal alteration processes. Wairakei andesites were chosen for comparison to Tompaso andesites, especially because of its different geological setting and geothermal reservoir structure. The results suggest that mineral composition and arrangement affect the preference of hydrothermal alteration on andesites.</p>

scholarly journals Geology and Geothermal Setting of Tompaso Geothermal System, Indonesia, with Comparisons of Andesite Alteration Patterns with Wairakei, New Zealand

2021 ◽  
Author(s):  
◽  
Kartika Palupi Savitri
Keyword(s):  
Hydrothermal Alteration ◽  
Short Wave ◽  
Age Dating ◽  
Core Material ◽  
Geothermal System ◽  
Scattered Electron ◽  
Subsurface Geology ◽  
North Sulawesi ◽  
Alteration Processes ◽  
First Time

<p>Tompaso geothermal system is a typical volcanic arc geothermal system in North Sulawesi, Indonesia. Although situated close to the Tondano caldera, subsurface lithologies and structures do not show any evidence for caldera-related features and the system is inferred to be related to the andesitic Soputan volcano. The subsurface geology of Tompaso consists of Tuff B unit, Rhyolite unit, Andesite B unit, Pitchstone unit, Pyroclastic Breccia unit,Andesite A unit, Pumice unit, and Tuff A unit, respectively, from the oldest penetrated unit. The silicic Pitchstone and Rhyolite units are presumed to be sourced from the same magma chamber. Petrological and mineralogical observations using binocular and petrographic microscopy, short-wave infrared (SWIR) analysis, and back-scattered electron (BSE) imaging combined with energy dispersive X-ray spectroscopy (EDS) have been applied to cuttings and limited core material from three boreholes: LHD-26, LHD-27, and LHD-32. Age dating has not been undertaken and, thus, conclusions on correlations between subsurface geology inferred here with surface formation groupings from previous works cannot be drawn.  Tompaso geothermal system is characterised primarily by variations in the fracturing within the reservoir. Secondary mineralogy and the structure of present-day temperature of the system suggest that the movement of hydrothermal fluids at Tompaso is controlled by faults: the Soputan, Tempang, and A-A’ faults, the last defined for the first time in this thesis. Soputan Fault controls the outflow of the system. On the other hand, the influence of Tempang and A-A’ faults is dominant only in the upper portion of the system. The A-A’ fault likely acts as a channel for cooler meteoric surface water, while the Tempang Fault is inferred to have experienced self-sealing and appears to be an impermeable structure in the system. The self-sealing process of the Tempang Fault and/or the introduction of meteoric water through the A-A’ fault may be related to the cooling of the northern and western part of the system.  The challenges in identifying protoliths in active geothermal areas is addressed here through studies of the influence of andesite textures on the preferences of hydrothermal alteration processes. Wairakei andesites were chosen for comparison to Tompaso andesites, especially because of its different geological setting and geothermal reservoir structure. The results suggest that mineral composition and arrangement affect the preference of hydrothermal alteration on andesites.</p>

scholarly journals Lithofacies from the 1963-1967 Surtsey eruption in SUSTAIN drill cores SE-2a, SE-2b and SE-03

2020 ◽  
Vol 14 ◽  
pp. 19-32
Author(s):  
Jocelyn McPhie ◽  
James D.L. White ◽  
Carolyn Gorny ◽  
Marie D. Jackson ◽  
Magnús Tumi Gudmundsson ◽  
...  
Keyword(s):  
Hydrothermal Alteration ◽  
Sedimentary Facies ◽  
Drill Hole ◽  
Explosive Eruptions ◽  
Volcanic System ◽  
Sea Floor ◽  
Alteration Processes ◽  
Lapilli Tuff ◽  
Drill Holes ◽  
Drill Cores

Surtsey was drilled in 2017 in the context of the Surtsey Underwater volcanic System for Thermophiles, Alteration processes and INnovative Concretes (SUSTAIN) project. Vertical drill holes, SE-02a and SE02b (drilled to 191.64 m), and angled drill SE-03 (drilled to 354.05 m), intersected armoured lapilli tuff and lapilli tuff generated mainly by explosive eruptions at Surtur from November 1963 to January 1964. The top ~20 m of lapilli tuff was erupted from Surtungur. Intervals of coherent basalt in SE-02b (15.7 to 17 m and <15 cm at the end) and in SE-03 (<1 m at ~60 m and ~238 m, and 10 m near the base) are probably intrusions that may have fed the small lavas erupted at Surtur ~2.5 years later. Although collared only a few m from the 1979 drill hole, neither SE-02a nor SE-02b intersected the 13-m-thick interval of basalt found in the 1979 drill hole. The 2017 drill cores are entirely lithified and variably altered, reflecting the effects of hydrothermal alteration and cement deposition on the originally fresh, unconsolidated ash and lapilli. Drill hole SE-03 was drilled on an azimuth of 264o and at 55o from horizontal, obliquely crossing the crater- and conduit-fill of Surtur. Although the exact trajectory of SE-03 is unknown (the drill hole was not surveyed), the drill hole ended at a vertical depth of ~100 m below the pre-eruption sea floor, however, sedimentary facies known to underlie the sea floor nearby were not intersected. Surtur eruptions therefore excavated the pre-eruption sea floor to a depth of several tens of m.

Hydrothermal alteration processes of the Tertiary lavas of Northern Ireland

2001 ◽  
Vol 65 (4) ◽  
pp. 543-554 ◽  
Author(s):  
Ch. Robert
Keyword(s):  
Hydrothermal Alteration ◽  
Local Perturbation ◽  
Fluid Composition ◽  
Lava Sequence ◽  
Long Time ◽  
History Of ◽  
Alteration Minerals ◽  
Alteration Processes ◽  
Flow Through ◽  
Trioctahedral Smectites

AbstractThe alteration mineralogy of two outcrops of basaltic lavas in northeast Ireland is studied with respect to the hydrothermal alteration history of basalts. Evidence for contact between basaltic flows and palaeorivers or palaeolakes is reported in both outcrops, which belong to two different formations: the Lower Basaltic Formation (LBF) and the Inter Basaltic Formation (Causeway Tholeiite Member, CTM). The secondary minerals consist of layer silicates (chlorite-smectite, C-S, di- and trioctahedral smectites), zeolites, calcite and silica minerals and there is a repetition of the sequence of alteration mineralogy in each formation. The mineralogy of phyllosilicates from the LBF (C-S) corresponds to hotter conditions of alteration than those of CTM (di/trioctahedral smectites), while the zeolite mineralogy is controlled by the fluid composition. In consequence, the mineralogy and the distribution of alteration minerals suggest that the crystallization of phyllosilicates and zeolites did not develop during burial of lavas a long time after the eruption, but reflects thermal gradients driven by lava heat flow and marked by local perturbation caused by regional water flow through the aquifer zone in the lava during the last cooling of each lava sequence.

High-charge to low-charge smectite reaction in hydrothermal alteration processes

Clay Minerals ◽  
1988 ◽  
Vol 23 (2) ◽  
pp. 133-146 ◽  
Author(s):  
A. Bouchet ◽  
D. Proust ◽  
A. Meunier ◽  
D. Beaufort
Keyword(s):  
Hydrothermal Alteration ◽  
Measurement Techniques ◽  
Wall Rock ◽  
Hydrothermal Conditions ◽  
High Charge ◽  
X Ray ◽  
External Sources ◽  
Alteration Processes ◽  
Low Charge ◽  
Hydrothermal Veins

AbstractIllite/smectite mixed-layered minerals (I/S) occurring in hydrothermally altered dacite from the island of Martinique were studied using X-ray powder diffraction, electron microprobe and CEC measurement techniques. Microprobe analyses and X-ray identification of high- and low-charge smectite layers indicate that the I/S hydrothermal alteration operates from wall-rock to hydrothermal veins, with conversion of high-charge to low-charge smectite and formation of illite layers. The overall alteration reaction can be expressed as: mixed-layered high-charge smectite + Si4+ + K+ → mixed-layered low-charge smectite + illite. This reaction requires Si and K from external sources and differs from the currently invoked mechanisms for diagenetic illitization where Si is released. The proposed reaction appears, therefore, to be the first step of I/S alteration under low-temperature hydrothermal conditions, prior to the crystallization of newly-formed I/S.

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