Origins of calcite in a boiling geothermal system

Simmons, S. W.; Christenson, Bruce

doi:10.2475/ajs.294.3.361

Cited by 283 publications

(154 citation statements)

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“…The typical radial texture of calcite observed in the field and the supposed conditions of precipitation (i.e. during fluid immiscibility) are indicative of a high rate of precipitation of the carbonatic phase (Simmons and Christenson 1994). Relatively high levels of Sr in calcite further confirm this hypothesis, since the co-precipitation of elements with distribution coefficient <1, like Sr, is enhanced by high rates of precipitation (Kele et al 2008).…”

Section: Mineralogy Of Castelnuovo Dell'abate Travertine Depositsupporting

confidence: 64%

Investigating fossil hydrothermal systems by means of fluid inclusions and stable isotopes in banded travertine: an example from Castelnuovo dell’Abate (southern Tuscany, Italy)

Rimondi

Costagliola

Ruggieri

et al. 2015

Int J Earth Sci (Geol Rundsch)

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Section: Mineralogy Of Castelnuovo Dell'abate Travertine Depositsupporting

confidence: 64%

Investigating fossil hydrothermal systems by means of fluid inclusions and stable isotopes in banded travertine: an example from Castelnuovo dell’Abate (southern Tuscany, Italy)

Rimondi

Costagliola

Ruggieri

et al. 2015

Int J Earth Sci (Geol Rundsch)

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“…The mineralogy and textures of the veins, particularly the bladed calcite, are thought to be indicative of deposition during fluid boiling (Browne 1978;Simmons & Christenson 1994). A detailed fluid inclusion study of these veins elsewhere (Craw 1997) suggests that they formed during boiling of CO2-bearing water, and the present data suggest an initial fluid composition of c. 5 mole% CO2.…”

Section: Euhedral Quartz-adularia Veinsmentioning

confidence: 57%

Structure and fluid migration in a late Cenozoic duplex system forming the Main Divide in the central Southern Alps, New Zealand

Cox¹,

Craw²,

Chamberlain³

1997

New Zealand Journal of Geology and Geophysics

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The Alpine Schist immediately west of the Main Divide of the Southern Alps is a west-dipping duplex system consisting of an imbricated stack of rock slabs, each c. 250-1000 m thick. The imbricated stack has low grade, little deformed pumpellyite-actinolite facies semischists at the base, overlain by progressively higher grade and more deformed schists. The structurally highest slab mapped consists of multiply-deformed biotite zone schist. The duplex lies on the hanging wall of the northwest-dipping Main Divide Fault Zone, which separates semischist from structurally underlying greywacke. Rock slabs are internally disrupted by faults subparallel to layering, and consist of lozenge-shaped blocks of 10-100 m. Fault zones separating rock slabs consist of <50 cm thick zones of weakly lithified cataclasite and soft gouge. Slickensides on fault surfaces plunge northwest. The duplex formed during late Cenozoic rise of the Southern Alps.Four generations of postmetamorphic veins cut rock slabs of the duplex system. The earliest veins contain quartz, chlorite, calcite, and sulphides and lie subparallel to foliation in the higher grade slabs only. A distinctive set of openspace-filling fissure veins in a lower greenschist facies slab contains euhedral quartz, adularia, bladed calcite, and chlorite. The whole duplex system is cut by steeply dipping shears and fractures containing quartz and ankerite infilling and breccia cementation. Late stage iron oxy-hydroxidecoated fractures, generally steeply dipping, cut all rock slabs. Pyrite and, locally, arsenopyrite accompanies quartz and ankerite veins in extensional sites of steeply dipping late stage fractures, and gold contents up to 850 ppb occur. This G96031Received 2 September 1996; accepted 9 May 1997 gold mineralisation occurred within c. 1 km of the surface and had epithermal affinities.Hydrothermal fluids mineralising the various fractures range in temperature between 350°C and near-ambient temperatures. The quartz-adularia-calcite veins formed at 0.5-2.5 km depth before duplex formation, and later veins formed at shallower levels after duplex formation. Vein carbonates have δ 18 O(SMOW) between 11.4 and26.1%o, and Δ 13 C(PDB) between -0.6 and -11.4%o. Calculated isotopic ratios for the mineralising fluids show little evidence for meteoric origin. The fluid may be meteoric water which has undergone isotopic exchange with host rocks, metamorphic water, or a mixture of these, and mineralisation occurred during rise of the fluids from depth.

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“…Steam-heated water currently fills the pore spaces and fractures near wells Br7 and Brl6 as determined from the down-hole composition of fluids leaking into the wells through casing breaks caused by corrosion (Hedenquist and Stewart, 1985). The presence of the water is consistent with the abundance of hydrothermal clay and calcite, and the isotopic compositions of calcite in the altered rocks (Hedenquist, 1990;Simmons and Christenson, 1994). Alteration mineral assemblages and fluid inclusion data from well Brl6 indicated the former existence of boiling temperatures, however, implying that the present temperatures caused by steam-heated water were preceded by higher temperatures (Simmons and Browne, 1997).…”

Section: S a M P L E D E S C R I P T I O N Smentioning

confidence: 59%

Genesis of Dioctahedral Phyllosilicates During Hydrothermal Alteration of Volcanic Rocks: II. The Broadlands-Ohaaki Hydrothermal System, New Zealand

Yan

Tillick

Peacor

et al. 2001

Clays and clay miner.

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Abstract--The clay mineral textures, assemblages, formation mechanisms, and controlling geological parameters relating to alteration of silicic volcanic rocks by hydrothermal solutions, in core samples from the Broadlands-Ohaaki hydrothermal system, New Zealand, were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission and analytical electron microscopy (TEM/ AEM). Mineralogical and textural relations of this active hydrothermal system, for which temperatures and fluid relations are well known, are equivalent to those in the Golden Cross hydrothermal gold deposit as described in Part 1.XRD data show a sequence of clay minerals from smectite to a range of interstratified I-S to mica with increasing depth and temperature, on average. TEM observations are in general agreement with XRD data, especially with respect to relative proportions of illite (I)-and smectite (S)-like layers. TEM data also show that: (1) Smectite packets contain no discrete illite-like layers in samples identified as (Reichweite, R = 0) I-S by XRD. They coexist with separate packets of (R = 1) I~S. (2) A continuous range in I-S occurs from (R = 1) I-S with increasing proportion of illite-like layers, but at high illite-like layer contents there is a gap between I-S and illite. (3) 1M and 2M] polytypes of mica coexist in separate packets, but the rare 1M polytype has a larger VlMg content.The data imply that clay minerals formed by dissolution and neocrystallization directly from volcanic phases, although multiple reaction events can not be ruled out. Such "episodic" alteration produces a sequence of clay minerals identical to those of prograde diagenesis of pelitic sediments. This result implies that the presence of a continuous sequence is not definitive proof of continuous sequences of transformation as a function of time and continuous burial. Reaction progress of the clay-mineral sequence is in general accord with the known temperature gradient, but with significant and common exceptions. High porosity and permeability, both inherent in rock texture and local structure, are inferred to fbster local reaction progress, as consistent with metastability of phases and the Ostwald step rule.

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Origins of calcite in a boiling geothermal system

Cited by 283 publications

References 0 publications

Investigating fossil hydrothermal systems by means of fluid inclusions and stable isotopes in banded travertine: an example from Castelnuovo dell’Abate (southern Tuscany, Italy)

Investigating fossil hydrothermal systems by means of fluid inclusions and stable isotopes in banded travertine: an example from Castelnuovo dell’Abate (southern Tuscany, Italy)

Structure and fluid migration in a late Cenozoic duplex system forming the Main Divide in the central Southern Alps, New Zealand

Genesis of Dioctahedral Phyllosilicates During Hydrothermal Alteration of Volcanic Rocks: II. The Broadlands-Ohaaki Hydrothermal System, New Zealand

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