Hydrothermal Fluids

1996 ◽  
Author(s):  
Craig M. Bethke
Keyword(s):  
Hot Springs ◽  
Geochemical Modeling ◽  
Ore Deposits ◽  
Hydrothermal Fluids ◽  
Mississippi Valley ◽  
Midocean Ridges ◽  
First Case ◽  
Modeling Software ◽  
Geochemical Models ◽  
Ore Deposition

Hydrothermal fluids, hot groundwaters that circulate within the Earth’s crust, play central roles in many geological processes, including the genesis of a broad variety of ore deposits, the chemical alteration of rocks and sediments, and the origin of hot springs and geothermal fields. Many studies have been devoted to modeling how hydrothermal fluids react chemically as they encounter wall rocks, cool, boil, and mix with other fluids. Such modeling proliferated in part because hydrothermal fluids are highly reactive and because the reaction products are commonly well preserved, readily studied, and likely to be of economic interest. Further impetus was provided by the development of reliable modeling software in the 1970s, a period of concern over the availability of strategic and critical minerals and of heightened interest in economic geology and the exploitation of geothermal energy. As a result, many of the earliest and most imaginative applications of geochemical modeling, beginning with Helgeson’s (1970) simulation of ore deposition in hydrothermal veins and the alteration of nearby country rock, have addressed the reaction of hydrothermal fluids. For example, Reed (1977) considered the origin of a precious metal district; Garven and Freeze (1984), Sverjensky (1984, 1987), and Anderson and Garven (1987) studied the role of sedimentary brines in forming Mississippi Valley-type and other ore deposits; Wolery (1978), Janecky and Seyfried (1984), Bowers et al. (1985), and Janecky and Shanks (1988) simulated hydrothermal interactions along the midocean ridges; and Drummond and Ohmoto (1985) and Spycher and Reed (1988) modeled how fluid boiling is related to ore deposition. In this chapter, we develop geochemical models of two hydrothermal processes: the formation of fluorite veins in the Albigeois ore district and the origin of “black smokers, ” a name given to hydrothermal vents found along the ocean floor at midocean ridges. As a first case study, we borrow from the modeling work of Rowan (1991), who considered the origin of fluorite (CaF2) veins in the Albigeois district of the southwest Massif Central, France. Production and reserves for the district as a whole total about 7 million metric tons, making it comparable to the more famous deposits of southern Illinois and western Kentucky, USA.

Pétrographie et altération de la matière organiquedu gisement de plomb–zinc–cuivre de tourist–Bou Beker,Maroc nord oriental

1996 ◽  
Vol 33 (10) ◽  
pp. 1363-1374 ◽  
Author(s):  
M. Bouadellah ◽  
A. C. Brown ◽  
Y. Héroux
Keyword(s):  
Organic Matter ◽  
Ore Deposits ◽  
Mississippi Valley ◽  
Sulfide Mineralization ◽  
Mineralization Process ◽  
Associated Gas ◽  
Regional Flow ◽  
Lead Zinc ◽  
Reflectance Measurements ◽  
Ore Deposition

Reflectance measurements and organic petrography were used to study altered organic matter in the dolomitic Middle Jurassic Beddiane sequence hosting the Beddiane lead–zinc deposit. Organic matter occurs in the lower dolostone units of the formation where zinc sulfide mineralization prevails. The upper units, where lead sulfide mineralization is dominant, contain lesser amounts of organic matter. The organic matter in the Beddiane sequence consists of macerals, amorphous kerogen, and solid bitumen, inertinite and vitrinite are ubiquitous. The amount of exinite increases toward mineralized areas but the ratio exinite/kerogen remains constant. Two types of vitrinite are considered on the basis of their reflectance: Vt1 with low reflectance values (0.3–0.5%) and Vt2 with higher values (0.7–1.25%). The ratio Vt1/Vt2 increases and the reflectance values for Vt1 decrease toward the zinc-prevailing units, Organic matter associated with the mineralization exhibits features such as oxidation halos and desiccation cracks, together with a low-fluorescent exinite. The association of the kerogen content, the trend in reflectance values, and the alteration features of the Mississippi Valley-type Beddiane deposit support the hypothesis that the regional flow of hot brines associated with the mineralization process was the cause of anomalous heating, that the occurrence of exinite maceral and its associated gas played a role in the ore deposition, and that the new chemical equilibrium reached by the zinc-dominant host rock after ore deposition is responsible for the suppressed reflectance values within and near the ore deposits.

scholarly journals Radiogenic Pb Enrichment of Mississippi Valley-Type Metallic Ore Deposits, Southern Ozarks: Constraints Based on Geochemical Studies of Source Rocks and Their Diagenetic History

Geosciences ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 172
Author(s):  
Jonathan Chick ◽  
Sydney E. McKim ◽  
Adriana Potra ◽  
Walter L. Manger ◽  
John R. Samuelsen
Keyword(s):  
Linear Trend ◽  
Ore Deposits ◽  
Source Rocks ◽  
Mississippi Valley ◽  
Isotopic Signatures ◽  
Boone Formation ◽  
Tripolitic Chert ◽  
Geochemical Studies ◽  
Mississippi Valley Type ◽  
Valley Type

Southern Ozark Mississippi Valley-type ores are enriched in radiogenic Pb, with isotopic signatures suggesting that metals were supplied by two end-member components. While the less radiogenic component appears to be derived from various shale and sandstone units, the source of the more radiogenic component has not yet been identified. Analyses of cherts from the Early Ordovician Cotter Dolomite and tripolitic chert from the Early Mississippian Boone Formation contain highly radiogenic Pb, with isotopic ratios comparable to those of ores. However, most samples have lower 208Pb/204Pb and 207Pb/204Pb for a given 206Pb/204Pb compared to ores. These relationships demonstrate that the enriched Pb isotopic values of the ore array cannot be related to the host and regional lithologies sampled, suggesting that the source of high ratios may lay further afield. The slope of the linear trend defined by the Pb isotope ratios of ores corresponds to an age of about 1.19 Ga. Therefore, an alternative for the linear array is the involvement of Precambrian basement in supplying ore Pb. Rare earth element patterns show that diagenetic processes involving the action of groundwater and hydrothermal fluids affected the sampled lithologies to various degrees, with Cotter Dolomite having experienced the highest degree of alteration.

scholarly journals Geochemical Modeling of Scale Formation due to Cooling and CO2-degassing in San Kamphaeng Geothermal Field, Northern Thailand

2021 ◽  
Vol 20 (3) ◽  
Author(s):  
Sutthipong Taweelarp ◽  
Supanut Suntikoon ◽  
Thaned Rojsiraphisal ◽  
Nattapol Ploymaklam ◽  
Schradh Saenton
Keyword(s):  
Carbon Dioxide ◽  
Hot Springs ◽  
Hot Spring ◽  
Geochemical Modeling ◽  
Chemical Properties ◽  
Geothermal Field ◽  
Spring Water ◽  
Northern Thailand ◽  
Scaling Potential ◽  
Co2 Degassing

Scaling in a geothermal piping system can cause serious problems by reducing flow rates and energy efficiency. In this work, scaling potential of San Kamphaeng (SK) geothermal energy, Northern Thailand was assessed based on geochemical model simulation using physical and chemical properties of hot spring water. Water samples from surface seepage and groundwater wells, analyzed by ICP-OES and ion chromatograph methods for chemical constituents, were dominated by Ca-HCO3 facies having partial pressure of carbon dioxide of 10–2.67 to 10–1.75 atm which is higher than ambient atmospheric CO2 content. Surface seepage samples have lower temperature (60.9°C) than deep groundwater (83.1°C) and reservoir (127.1°C, based on silica geothermometry). Geochemical characteristics of the hot spring water indicated significant difference in chemical properties between surface seepage and deep, hot groundwater as a result of mineral precipitation along the flow paths and inside well casing. Scales were mainly composed of carbonates, silica, Fe-Mn oxides. Geochemical simulations based on multiple chemical reaction equilibria in PHREEQC were performed to confirm scale formation from cooling and CO2-degassing processes. Simulation results showed total cumulative scaling potential (maximum possible precipitation) from 267-m deep well was estimated as 582.2 mg/L, but only 50.4% of scaling potential actually took place at SK hot springs. In addition, maximum possible carbon dioxide outflux to atmosphere from degassing process in SK geothermal field, estimated from the degassing process, was 6,960 ton/year indicating a continuous source of greenhouse gas that may contribute to climate change. Keywords: Degassing, Geochemical modeling, PHREEQC, San Kamphaeng Hot Springs, Scaling

scholarly journals COMPUTER CODES OF GEOCHEMICAL MODELING USED TO WATER-ROCK INTERACTION SIMPLE AND COMPLEX SYSTEMS

2019 ◽  
Vol 16 (32) ◽  
pp. 108-118
Author(s):  
Marcos Antônio KLUNK ◽  
Sudipta DASGUPTA ◽  
Mohuli DAS ◽  
Paulo Roberto WANDER
Keyword(s):  
Complex Systems ◽  
Geochemical Modeling ◽  
Chemical Properties ◽  
Coupled Transport ◽  
Burial History ◽  
Batch Mode ◽  
Data Set ◽  
Rock Interaction ◽  
Geochemical Reactions ◽  
Geochemical Models

The numerical modeling of transport and reaction was used for the understanding of the evolution of the diagenetic processes and their importance in the characterization and prediction of oil reservoir quality. Geochemical models are represented by numerical equations based on the physical-chemical properties of minerals. There are many software’s available in the market to simulate systems and geochemical reactions. The codes are divided into three distinct categories: coupled transport of reaction, modeling speciation, and batch mode according to the numerical method. Simple systems have clear connections between inputs and outputs. Complex systems have multiple factors that provide a probability distribution of data inputs that interact in specific functions. The outputs produced as a result are therefore impossible to predict with complete accuracy. Several research groups tried to develop numerical codes for geochemical modeling. The critical factors for the use of these systems are (i) verification of the simulation results with empirical data set and (ii) sensitivity analysis of these results, for the construction of general models which provide a predictive character. This last factor is particularly important as it establishes the qualitative and quantitative impact of each parameter in the simulations. Thus, with a complete numerical model diagenetic, it is possible to perform various simulations modifying one or the other parameter to test the sensitivity in the construction of these different geological scenarios. This set includes mineral composition and texture, the composition of fluids, paragenetic sequence, and burial history. This work brings fundamental concepts related to this topic as well as an analysis of commercial software available.

Multi-Stage Fluid System Responsible for Ore Deposition in the Ossa-Morena Zone (Portugal): Constraints in Cu-Ore Deposits Formation

2020 ◽  
Vol 62 (6) ◽  
pp. 508-534
Author(s):  
M. Maia ◽  
N. Moreira ◽  
S. Vicente ◽  
J. Mirão ◽  
F. Noronha ◽  
...  
Keyword(s):  
Ore Deposits ◽  
Fluid System ◽  
Multi Stage ◽  
Ore Deposition

Origin and formation model of Eocene dolomite in the upper Niubao Formation of Lunpola Basin, Tibetan Plateau

2021 ◽  
pp. 1-50
Author(s):  
Xiaoquan Chen ◽  
Fengcun Xing ◽  
Shu Jiang ◽  
Yongchao Lu ◽  
Zhongrong Liu ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Hot Springs ◽  
Northern China ◽  
Hydrothermal Fluids ◽  
Lake Basin ◽  
The Tibetan Plateau ◽  
Climate Conditions ◽  
Hot Climate ◽  
Strong Evaporation ◽  
Semi Arid

Using fresh cores samples, we determined the origin and formation process of Eocene lacustrine dolomites in the Tibetan Plateau through petrological, mineralogical, and geochemical analyses. Dolomitic rocks were collected from the upper member of Eocene Niubao Formation in the Lunpola Basin, and consist of dolomitic mudstone, argillaceous dolomite, dolomite-bearing mudstone and mud-bearing dolomite. These dolomites are dominated by aphanotopic and micro-crystalline dolomites, with minor amounts of euhedral or subhedral powder- and fine-crystalline dolomites. Carbon and oxygen stable isotopes, combined with ubiquitous gypsum in study area, indicates a semi-saline continental lake under strong evaporative conditions. The revealed relatively high temperature of dolomitization(33.8°C–119.1°C), combined with hydrothermal minerals such as cerous phosphate and barite, reflect the participation of dolomite from hot fluids. Moreover, the inferred dolomitization temperatures decrease gradually toward the centre of the lake basin, suggesting the resurgence of hydrothermal fluids along a fault zone on the lake margin. This proves that frequent thermal events occurred at the boundary fault of the Lunpola Basin margin during early Himalayan orogenesis. In addition, Jurassic carbonates interacting with hydrothermal fluids, as well as strong evaporation conditions, likely provided favourable conditions for the formation of primary lime sediments. A rich source of Mg2+ brought by volcanic ash, hydrothermal fluids, and the Jurassic carbonates then created conditions for dolomitization during the depositional period. Strong evaporation under a relatively hot climate enhanced penecontemporaneous dolomitization, thus forming dolomite. Tibetan Plateau was under arid to semi-arid climate conditions, and there was a widespread distribution of dolostones in western, central, and northern China during the Eocene period. The hydrothermal dolomites of the upper Niubao Formation testify for active hot springs, while lacustrine dolomite imply arid or semi-arid climates during the Eocene, in the early stages of Himalayan orogenesis.

Magmatic-Hydrothermal Fluids

Elements ◽  
2020 ◽  
Vol 16 (6) ◽  
pp. 401-406 ◽  
Author(s):  
Andreas Audétat ◽  
Marie Edmonds
Keyword(s):  
Metal Content ◽  
Fluid Phase ◽  
Volcanic Eruptions ◽  
Hydrothermal Systems ◽  
Ore Deposits ◽  
Hydrothermal Fluids ◽  
Geological Processes ◽  
Mineral Growth ◽  
Fluid Saturation ◽  
Fluid Phase Equilibria

Magmatic-hydrothermal fluids play a key role in a variety of geological processes, including volcanic eruptions and the formation of ore deposits whose metal content is derived from magmas and transported to the site of ore deposition by means of hydrothermal fluids. Here, we explain the causes and consequences of fluid saturation in magmas, the corresponding fluid-phase equilibria, and the behavior of metals and ligands during the transition from magma to an exsolved hydrothermal fluid. Much of what we know about magmatic-hydrothermal systems stems from the study of fluid inclusions, which are minute droplets of fluids trapped within minerals during mineral growth.

Uniqueness

1996 ◽  
Author(s):  
Craig M. Bethke
Keyword(s):  
Geochemical Modeling ◽  
Theoretical Work ◽  
Input Constraints ◽  
Governing Equations ◽  
Single Root ◽  
Rate Laws ◽  
Starting Point ◽  
The Subject ◽  
Geochemical Models ◽  
Practical Question

A practical question that arises in quantitative modeling is whether the results of a modeling study are unique. In other words, is it possible to arrive at results that differ, at least slightly, from the original ones but nonetheless satisfy the governing equations and honor the input constraints? In the broadest sense, of course, no model is unique (see, for example, Oreskes et al., 1994). A geochemical modeler could conceptualize the problem differently, choose a different compilation of thermodynamic data, include more or fewer species and minerals in the calculation, or employ a different method of estimating activity coefficients. The modeler might allow a mineral to form at equilibrium with the fluid or require it to precipitate according to any of a number of published kinetic rate laws and rate constants, and so on. Since a model is a simplified version of reality that is useful as a tool (Chapter 2), it follows that there is no“correct” model, only a model that is most useful for a given purpose. A more precise question (Bethke, 1992) is the subject of this chapter: in geochemical modeling is there but a single root to the set of governing equations that honors a given set of input constraints? We might call such a property mathematical uniqueness, to differentiate it from the broader aspects of uniqueness. The property of mathematical uniqueness is important because once the software has discovered a root to a problem, the modeler may abandon any search for further solutions. There is no concern that the choice of a starting point for iteration has affected the answer. In the absence of a demonstration of uniqueness, on the other hand, the modeler cannot be completely certain that another solution, perhaps a more realistic or useful one, remains undiscovered. Geochemists, following early theoretical work in other fields, have long considered the multicomponent equilibrium problem (as defined in Chapter 3) to be mathematically unique. In fact, however, this assumption is not correct. Although relatively uncommon, there are examples of geochemical models in which more than one root of the governing equations satisfy the modeling constraints equally well. In this chapter, we consider the question of uniqueness and pose three simple problems in geochemical modeling that have nonunique solutions.

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