Salty Matters

The Blog is written by me, John Warren. Once every three or four weeks or so I will post an article or two on an evaporite topic that has piqued my interest. On the Saltwork Publications webpage (under "the Works") there is a growing library of pdfs and epubs based on these blogs. These articles on the website have much higher resolution extractable graphics in than in the blog. There is also a link to this set of pdfs and epubs on the home page (www.saltworkconsultants.com).

Volatile evaporite interactions with magma Part 1 of 2: Indications of hydrated salts?

John Warren - Sunday, February 10, 2019

Introduction

Direct and indirect interactions between magma and evaporites at a regional scale are neither well documented, nor well understood. Mostly, this is because little or no salt remains once the high-temperature interactions have run their course; instead, there is a suite of indirect geochemical and indicator-mineral assemblages (Warren, 2016). Aside from the presence of what can be ambiguous indicator suites, some hard-rock geologists with a career working in igneous and metamorphic terranes may not be well versed in textures indicative of the former presence of sedimentary evaporites, nor their varying volatility, nor their meta-evaporitic and meta-igneous siblings.

The term pyrometasomatic encompasses some, but not all, of the types of salt-magma interaction and reactions that occur when evaporites and molten magmas of different types are nearby. Styles of evaporites interactions with magma are a spectrum, with two endmember situations; 1) orthomagmatic (salt-assimilative and internal to the magma), and 2) paramagmatic (salt-interactive and external to the magma). Both encompass outcomes that can include a variety of substantial ore deposits (Warren, 2016; Chapter 16). Only in situations where igneous sills and dykes have intruded salt masses, with contacts preserved, can direct effects of magma-salt interaction be documented. Even then, determining the timing of the evaporite igneous interaction can be problematic; one must ask if the chemistry and texture indicate, 1) syn-igneous emplacement, or 2) post-emplacement alteration and deeply circulating groundwater flushing, or 3) a combination.

Orthomagmatic and paramagmatic evaporite associations are distinct from occurrences of primary igneous/magmatic anhydrites, which precipitate from sulphate-saturated melts. Igneous anhydrite forms independently of any sedimentary evaporite assimilation, as seen, for example, in anhydrite crystals crystallised in trachyandesitic pumice erupted from El Chichón Volcano in 1982, or in dacitic pumices erupted from Mount Pinatubo in 1991 and in acidic lavas in the Yanacocha district of northern Peru (Luhr et al., 2008; Chambefort et al., 2008). These evaporite assimilations are also distinct from fumarolic anhydrite, which precipitates where groundwaters and sulphur-bearing magmatic fluids interact, as on Usu Volcano, Hokkaido, and many central American and Andean volcanoes such as El Laco (Zimbelman et al., 2005). Likewise, they are distinct from the anhydrite precipitates (white smokers) in and below submarine vents across numerous mid-oceanic ridges (Humphris et al., 1995). See Warren 2016 (Chapter 16) for more geological detail on these non-evaporite-igneous anhydrite occurrences.

Cooking with salt (thermal decomposition of hydrated versus non-hydrated salts)

Perhaps the most critical factor controlling the local intensity of magmatic interaction with an evaporitic country rock is whether or not the sedimentary evaporite assemblage, in proximity to an igneous heat source, contains abundant hydrated salts, such as gypsum, polyhalite or carnallite. Hydrated evaporite salts, when interacting with the igneous realm, are highly volatile and likely to decompose. They tend to release their water of crystallisation at temperatures many hundreds of degrees below the melting points of their anhydrous counterparts (Table 1).


In contrast, anhydrous salts, such as halite beds intruded by igneous dykes or sills, are much less reactive. At a local scale (measured in metres) with respect to an intrasalt-igneous interaction, there are a number of documented thermally-driven alteration styles, typically created by the intrusion of dolerite dykes and sills into cooler halite, or the outflow of extrusive igneous flows over cooler halite beds (Knipping and Herrmann, 1985; Knipping, 1989; Grishina et al, 1992, 1998; Gutsche, 1988; Steinmann et al., 1999; Wall et al., 2010). Hot igneous material interacts with somewhat cooler anhydrous salt masses, typically halite or anhydrite, to create narrow but distinct heat and mobile fluid-release envelopes(Figure 1), also reflected in the resulting recrystallised inclusion-modified salt textures (Figure 2).


Based on studies of inclusion chemistry and homogenization temperatures in fluid inclusions in bedded halite near intrusives, it seems that the extent of the influence of a dolerite sill or dyke in bedded salt is marked by fluid (brine)-inclusion migration. This is evidenced by the disappearance of chevron structures and consequent formation of clear (sparry) recrystallised halite, with a new set of higher-temperature brine inclusions located at intercrystal or polyhedral intersections. Such a migration envelope is documented in bedded Cambrian halites intruded by end-Permian dolerite dykes in the Tunguska region of Siberia (Figure 2; Grishina et al., 1992). There, as a rule of thumb, an alteration halo extends up to twice the thickness of the dolerite sill above the sill and almost the thickness of the sill below (Figure 1).

Four inclusion type associations were found in halite as a function of the ratio of the distance of the sample from the intrusion contact (d) to the thickness of the intrusion (h), i.e. d/h (Figure 2). Chevron structures with aqueous inclusions progressively disappear as d/h decreases; the disappearance of chevrons occurs at greater distances above than below the intrusive sill. At d/h < 5 above the sill, a low-density CO2 vapour phase appears in brine inclusions, at d/h < 2 H2S-bearing liquid-CO2 inclusions appear, sometimes associated with carbonaceous material and orthorhombic S8, and for d/h < 0.9, CaCl2, CaCl2.KCl and nCaCl2.n MgCl2 solids occur in association with free water and liquid CO2 inclusions, with H2S, SCO, and Sg. The d/h values marking the transitions outlined above are lower below the sills than above. The water content of the inclusions progressively decreases on approaching the sills, whereas their CO2 content and density increase. Carnallite, sylvite and calcium chloride can occur as solid inclusions in the two associations nearest to the sill for d/h<2. Carnallite and sylvite occur as daughter minerals in brine inclusions. The presence of carbon dioxide is taken to indicate fluid circulation and dissolution/recrystallisation phenomena induced by the basalt intrusions. The origin of carbon dioxide is likely related to carbonate dissolution during magmatism (see Salty Matters, Oct 31, 2016).


In some shallow locations, relatively rapid magma emplacement can lead to linear breakout trends outlined by phreatomagmatic or phreatic explosion craters. Such phreatic explosion craters have been imaged on the Tertiary seafloor horizons in parts of the North Sea (Figure 3; Wall et al., 2010). The dykes were emplaced into Paleozoic and Mesozoic sediments and have a common upper termination in Early Tertiary sediments. The dykes are part of the British Tertiary volcanic province emplaced some 58 Ma. These dykes are characterised by a narrow 0.5–2 km wide vertical disturbance of seismic reflections that have linear plan view geometry. Negative magnetic anomalies directly align with the vertical seismic disturbance zones and indicate the presence of underlying igneous material. Linear coalesced collapse craters are found above the dykes. The collapse craters formed above the dyke due to the release of volatiles at the dyke tip and resulting gaseous expansion and subsequent volume loss. According to Wall et al. (2010), the larger craters likely formed due to explosive phreatomagmatic interaction between magma and pore water. The linearly aligned collapse craters can be considered an Earth analogue to Martian pit chain craters.

A phreatic eruption, also called a phreatic explosion, ultravulcanian eruption or steam-blast eruption, occurs when magma heats ground or surface water and is a separate but related occurrence to a phreatomagmatic eruption. A phreatomagmatic deposit typically contains solid inclusions of magmatic (igneous) material, whereas debris tied to a phreatic deposit does not, but ties to the effects of juvenile and deeply circulated hydrothermal waters. Extreme temperatures associated with an emplaced magma (anywhere from 500 to 1,170 °C) can cause a near-instantaneous phase change to steam, so forming a phreatomagmatic deposit. That is, rapid heating results in an intense explosion made up of steam, water, ash, rock, and volcanic bombs. During the eruption of Mount St. Helens, hundreds of steam explosions preceded the1980 Plinian eruption of the volcano core. Many authors argue a less intense geothermal event results in a mud volcano, but there are many other active mud volcanoes worldwide that tie to compactional overpressure unrelated to any magma emplacement (Warren et al., 2011). As the published interpretation of aligned phreatic breakout structures illustrated in Figure 3 is based on seismic without well control, the explosion mechanism may be solely phreatic heating or phreatomagmatic.


Deposits of phreatic eruptions (as contrasted with a phreatomagmatic eruption) typically include steam and rock fragments without the inclusion of fragments derived from liquid magma, lava or volcanic ash. The temperature of the phreatic fragments can range from cool to incandescent. So if molten magma is present, the resulting explosive debris deposit is typically classified as a phreatomagmatic eruption. These eruptions can create broad, low-relief craters called maars. In contrast, phreatic explosions lack debris derived from molten (igneous) material, but emplacement can be accompanied by carbon dioxide or hydrogen sulfide gas emissions. CO2 can asphyxiate at sufficient concentration; H2S is a broad spectrum poison. A 1979 phreatic eruption on the island of Java killed 140 people, most of whom were overcome by poisonous gases. Phreatic eruptions, even if the deposit lacks igneous rock fragments, are typically classed as a type of volcanic eruptions because a phreatic eruption can force juvenile fluids to the surface. But when a phreatic explosion is related to an igneous feature intersecting an evaporite bed, the resultant textures show a contrast between heating of anhydrous and hydrous salts


Hydrous salt interactions in Germany

Textures created by an igneous intrusion into a variably-hydrated evaporite succession can be studied in the dyke-and sill-intruded halite levels exposed in the walls of potash mines of the Werra-Fulda district of Germany (Figure 4; Steinmann et al., 1999; Schofield et al., 2014). There, the Permian Zechstein salt series contains two important potash salt horizons (2-10m thick), which are mined at a depths ≈ 800 m, from within a 400m thick halite host (Figure 4a). In the later Tertiary, basaltic melts intruded these Zechstein evaporites, but it seems only a few dykes reached the Miocene landsurface. The basaltic melt ties to regional volcanic activity, some 10 to 25 Ma. Basalts exposed in the halite-dominant portions of the mine walls are typically subvertical dykes, rather than sills. The basaltic intervals intersect the salt over zones up to several kilometres wide (Figure 4b). However, correlations of individual dyke swarms, either between different mines, or between surface and subsurface outcrops is difficult.


From a paleogeographic perspective, the Werra-Fulda Basin is situated in a southern embayment of the European Zechstein Basin. It contains cyclic evaporites of the Werra Formation (Z1). In the Neuhof area, the evaporites of the Zechstein are underlain by siliciclastic rocks of the Permian Rotliegend interval. The higher Zechstein-cycles (Z2 – Z7), on top of the Werra Formation, consist of a siliciclastic succession with intercalated limestone and anhydrite layers (Strauch et al., 2018; Beer and Barnasch, 2018). The Werra Formation is dominated by rock salt with a thickness up to 300 m.

Two potash seams (Seam Hessen and Seam Thüringen) separate the rock salt of the Werra Formation into three distinct units (Figure 4b). Lower, Middle and Upper Werra rock salt). Seam Hessen mainly consists of hard salt (kieserite, sylvite, halite and anhydrite). It is overlain by several, potash mineral-bearing horizons which show a strong vertical and lateral heterogeneity and consist of kieserite, sylvite, carnallite, halite and anhydrite. Internally, three separate units are identified within the potash Seam Hessen (Figure 4). The “Wurmsalz”, a hard salt with up to four strongly folded anhydritic clay bands represents the lower part of Seam Hessen. The middle part consists of massive, kieserite-rich hard salt with abundant sylvite lenses (“Flockensalz”). The “Bändersalz”, a banded hard salt which is typically intercalated with brownish, halitic layers occurs in the upper part of Seam Hessen. Potash Seam Thüringen usually occurs around 50 m below Seam Hessen. Its lower part is dominated by a well-bedded hard salt with intercalated rock salt. Its upper part consists of a variety of rock types including carnallite, sylvite and hard salt.

In the Fulda region the thermally-driven release of water of crystallisation within particular Zechstein salt beds intersecting igneous dykes creates thixotropic or subsurface “peperite” textures in hydrated carnallitite ore layers, where heated water of crystallisation escaped from the hydrated-salt lattice. Dehydration-driven loss of mechanical strength focuses zones of magma entry into particular horizons in the salt mass, wherever hydrated salt layers were intersected (Figure 5b verses 5c). In contrast, dyke and sill margins are much sharper and narrower in zones of contact with anhydrous salt intervals (Figure 5a, d; Schofield et al., 2014).

Accordingly, away from the immediate vicinity of the direct thermal aureole, heated and overpressured dehydration waters can enter a former Zechstein carnallite halite bed, and drive the creation of extensive soft sediment deformation and peperite textures in the previous hydrated layer (Figure 5c, d). Mineralogically, sylvite and coarse recrystallised halite dominate the salt fraction in the peperite intervals/beds. These deformed beds formed within a hydrated salt bed and so differ from the conventional notion of volcanic peperites indicating water-saturated sediment interactions with very shallow dyke or sill emplacements.

Sylvite in these altered zones is a form of dehydrated carnallite, not a primary-textured salt. In the Fulda region, such altered zones and deformed units can extend along former carnallite layers to tens or even a hundred or more metres from the dyke feeder. Ultimately, the deformed potash bed passes laterally out into the unaltered bed, which can retain abundant inclusion-rich primary chevron halite and carnallite (Figure 5c versus 5d). That is, nearer the basalt dyke, the carnallite is transformed mainly into inclusion-poor halite and sylvite, the result of recrystallisation combined with incongruent flushing of warm saline fluids mobilised from the hydrated carnallite crystal lattice as it was heated and decomposed in response to nearby dyke emplacement. During such Miocene salt alteration/thermal metamorphism in the Fulda region, NaCl-rich diagenetic and juvenile fluids were mixed with fluids originating from thermally-mobilised crystallisation water in the carnallite as it converted to sylvite.

Nearer the basalt dyke, the carnallite is largely transformed into inclusion-poor halite and sylvite, the result of incongruent flushing of warm saline fluids mobilised from the hydrated carnallite crystal lattice as it was heated by dyke emplacement. During Miocene salt alteration/thermal metamorphism in the Fulda region, NaCl-fluids were mixed with fluids originating from thermally-mobilised crystallisation water in the carnallite, as it converted to sylvite. This brine mixture altered the basalts during post-intrusive cooling, an event which numerical models suggest was quite rapid (Knipping, 1989): a dyke of less than 0.5 m thickness probably cooled to temperatures less than 200°C within 14 days of dyke emplacement.

Worldwide, igneous dykes intersecting salt beds tend to widen to become sills in two zones: 1) along evaporite units within the halite mass that contain hydrated salts, such as carnallite or gypsum (Figure 5b, c) and, 2) where rising magma has ponded and so created laccoliths at the upper or lower halite contact with the adjacent nonsalt strata, or against a salt wall (Warren, 2016). The first alteration of the hydrated salt layer is a form of mineral alteration and recrystallisation in response to a pulse of released water/steam as dyke-driven heating forces the dehydration of hydrated salt layers. The second alteration is often folding and fluid-like disaggregation of the former, now dehydrated, layer in response to the mechanical strength contrast at a hydrated-nonhydrated salt-bed contact (Warren, 2016).

Surface expression of hydrated bedded salts interacting with magma in Dallol, Ethiopia

Local potash ores typify thermal sump depressions in the Dallol and Musley areas (Figure 6a, b, c, 7) where a similar set of subsurface destabilisation processes occurred when rising magma reached the levels of hydrated salts (kainite and carnallite beds) in the Houston Formation of the Danakhil depression fill (see Warren 2016 and Bastow et al. 2018 for more detailed discussion of the potash stratigraphy). To attain these hydrated salt levels the rising dyke swarm had passed relatively passively through the Lower Rocksalt Formation (Salty Matters, April 29, 2015). Emplacement of the magma/dykes into hydrated evaporites below the vicinity of what is now the Dallol Mound would have mobilised and deformed the hydrated potash salt level, converting carnallite to sylvite, kainite to bischofite and lesser kieserite, as well as creating widespread cavities filled with rising pressured volatiles carried by MgCl and KCl brines. Pressurisacreation of a cavernous network filled with volatiles at the level of the Houston Formation would have aided in forming the four-way dip closure now seen on the exposed and eroding salt beds that make up much of the Dallol Mound surface.


Once these hydrothermal cavities dissolved and breached the way to surface, the feeder brines cool and precipitate prograde salts such as halite, sylvite and bischofite. Such destabilisation has likely accommodated the emplacement of a basaltic sill at the level of the potash salts, in turn driving the uplift of the lake beds above this region outlined by the centripetal dips of the Dallol Mound. Mound-related uplift and hydrothermal activity then stimulate the formation of natural areas of ground collapse, sulphurous and acidic springs and fumaroles, along with the creation of water-filled chimneys and doline sags, filling with various hydrothermal salts, in the vicinity of the volcanic mound  (Figure 6).

That is this type of potash in the Dallol Mound region is hydrothermally reworked from the uplifted equivalents of the Houston Formation. Even today this hydrology is precipitating carnallitite (associated with bischofite and minor kieserite) in various hydrothermal brine pools atop and around the Dallol Mound, such as the carnallite-dominant Crescent deposit (Figure 7). These hydrothermal salts owe their origins to daylighting of pressurised fluid systems and cavities.


The last pressurised phreatic explosion crater formed in 1926. They were created by the volatile products of hydrated salt layers (Houston Fm) where these salts had come into contact with thermal aureoles or actual lithologies of newly emplaced dykes that had penetrated the underlying halite section. Volcanic rock fragments and other igneous debris have yet to make it to the surface in the Dallol Mound region, although active volcanic mounds and flows do cover the saltflat surface tens of kilometres to the south (Erte Alle ) and north. Based on the analogy exposed within the Zechstein-hosted potash mines of the Fulda region of Germany, it is likely that as well as creating at-surface brine pools, this hydrothermal dyke-related hydrology locally converts most subsurface carnallitite to a disturbed sylvinite bed at the level of contact with the Houston Fm.

Implications

It seems a "one-size-fits-all" model does not characterise magmatic interactions with massively bedded evaporites. Instead, there is a mineralogical control to the intensity of the interaction and the depth of thermal influence of recrystallisation and mobilisation textures. When a dyke-swarm intersects halite or anhydrite the thermally-driven recrystallisation and fluid migration halo is more limited, as outlined in Figure 1 and Figure 5a, d.

In contrast, when a dyke swarm intersects an interval containing hydrous salts such kainite, carnallite or gypsum, the heating drives the expulsion of the bound-water at decomposition temperatures much lower than the salts melting point (Table 1). Such hydrous-salt intervals devolatise, fluidise and flow, with the effects of the heating halo extending much further away from the heat source, driven in part by steam-driven hydrofracturing. On cooling, the resulting mineralogy in the highly-deformed bed is dominated by the anhydrous form of the devolatised salt, as in the sylvite unit after carnallite as seen in potash seams adjacent to dykes in the Fulda Region (Figures 5b, c).

Closer in to the heat source, the basalt that has moved in along the hydrous potash beds show abundant peperite textures (Figure 5c; Schofield et al., 2014). Actually, this is a unique form of peperite that is tied to beds of hydrous evaporite. It forms outside the usual scenario envisaged for peperite whereby molten igneous material interacts with wet sediment, with the water in the wet sediment held in interparticle pores.

The classic definition of a peperite is that it is a "genetic term applied to a rock formed essentially in situ by disintegration of magma intruding and mingling with unconsolidated or poorly consolidated, typically wet sediments. The term also refers to similar mixtures generated by the same processes operating at the contacts of lavas and other hot volcaniclastic deposits with such sediments" (Skilling et al. 2002).

In the case of the bedded hydrous salt intervals, before the intrusion of the igneous heat source, there was little to no free water, other than occasional brine inclusions in associated halite chevrons. What makes these hydrous-salt peperites interesting is that it is the igneous heating drives a mineralogic transformation in the hydrous salts that makes the formerly "dry" salt bed become "wet" sediment.

Before our work in the Fulda region (Schofield et al., 2014), the nature of igneous interactions with evaporites was understood to be mainly that documented by studies in areas with intrusives interacting with thick anhydrous halite and anhydrite beds. The heating haloes were seen as driving recrystallisation and brine migration over limited lateral distances of a few metres. However, the potash seam interactions in the Fulda region show this alteration distance can be much greater (hundreds of metres) id hydrous salt layers are heated.

The surface geology in the Dallol Mound region of Ethiopia shows an even more impressive set of igneous dyke hydrated salt interactions (Warren, 2016). There the potash interval known as the Houston Formation is a tens-of-metres thick section of hydrated salts below the upper halite unit and atop the lower halite. When the rising igneous dyke swarm rose to the level of Houston Formation, it drove a broad linear devolatisation zone in the dyke-heated alteration halo. This, in turn, forced the formation of the closed anticlinal uplift structure that is the Dallol mound. The release of MgCl2 during volatisation also explains phreatic breakout features that are outlined by at-surface collapse dolines with their hot (104-108°C) brine lakes and unusual bischofite (MgCl2) precipitates. Likewise, the same set of processes explains the occurrences of metres to tens of metres thick bischofite intervals that are intersected in cores in some of the potash exploration wells in the vicinity of Dallol Mound (pers. obs). These are likely cavity fill deposits formed as a byproduct of kainite and carnallite devolatisation sourced at the level of Houston Formation.

This set of more mobile brine fluid escape features has implications for nuclear waste storage in halite successions where a storage cavity may be in proximity to an interval of hydrous evaporite salts. Halite-hosted purpose-built caverns in thick evaporite intervals are one of the safest places in the world to store waste but perhaps not in parts of the salt succession that entrain beds of hydrous salts such as carnallite or kainite (Warren, 2017).

References

Bastow, I. D., A. D. Booth, G. Corti, D. Keir, C. Magee, C. A.-L. Jackson, J. Warren, J. Wilkinson, and M. Lascialfari, 2018, The development of late-stage continental breakup: Seismic reflection and borehole evidence from the Danakil Depression, Ethiopia: Tectonics, v. 37.

Beer, W., and L. Barnasch, in press, Werra-Fulda-Becken, SDGG- Monography.

Chambefort, I., J. H. Dilles, and A. J. R. Kent, 2008, Anhydrite-bearing andesite and dacite as a source for sulfur in magmatic-hydrothermal mineral deposits: Geology, v. 36, p. 719-722.

Grishina, S., J. Dubessy, A. Kontorovich, and J. Pironon, 1992, Inclusions in salt beds resulting from thermal metamorphism by dolerite sills (eastern Siberia, Russia): European Journal of Mineralogy, v. 4, p. 1187-1202.

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Humphris, S. E., P. M. Herzig, D. J. Miller, J. C. Alt, K. Becker, D. Brown, G. Brugmann, H. Chiba, Y. Fouquet, J. B. Gemmell, G. G., M. D. Hannington, N. G. Holm, J. J. Honnorez, G. J. Iturrino, R. Knott, R. Ludwig, K. Nakamura, S. Petersen, A. L. Reysenbach, P. A. Rona, S. Smith, A. A. Sturz, M. K. Tivey, and X. Zhao, 1995, The internal structure of an active sea-floor massive sulphide deposit: Nature, v. 377, p. 713-716.

Knipping, B., 1989, Basalt intrusions in evaporites: Lecture Notes in Earth Sciences (Springer-Verlag), v. 24, p. 132 pp.

Knipping, B., and A. G. Hermann, 1985, Mineralreaktionen und Stoff transporte an einem Kontakt Basalt-Carnallitit im Kalisalzhorizont Thüringen der Werra-Serie des Zechsteins: Kali und Steinsalz, v. 9, p. 111-124.

Luhr, J. F., 2008, Primary igneous anhydrite: Progress since its recognition in the 1982 El ChichÛn trachyandesite: Journal of Volcanology and Geothermal Research, v. 175, p. 394-407.

Schofield, N., I. Alsop, J. Warren, J. R. Underhill, R. Lehné, W. Beer, and V. Lukas, 2014, Mobilizing salt: Magma-salt interactions: Geology, v. 42, p. 599-602.

Skilling, I. P., J. D. L. White, and J. McPhie, 2002, Peperite: a review of magma–sediment mingling: Journal of Volcanology and Geothermal Research, v. 114, p. 1-17.

Steinmann, M., P. Stille, W. Bernotat, and B. Knipping, 1999, The corrosion of basaltic dykes in evaporites: Ar-Sr-Nd isotope and rare earth elements evidence: Chemical Geology, v. 153, p. 259-279.

Strauch, B., M. Zimmer, A. Zirkler, S. Höntzsch, and A. M. Schleicher, 2018, The influence of gas and humidity on the mineralogy of various salt compositions – implications for natural and technical caverns: Advances in Geoscience, v. 45, p. 227-233.

Wall, M., J. Cartwright, R. Davies, and A. McGrandle, 2010, 3D seismic imaging of a Tertiary Dyke Swarm in the Southern North Sea, UK: Basin Research, v. 22, p. 181-194.

Warren, J. K., 2016, Evaporites: A compendium (ISBN 978-3-319-13511-3): Berlin, Springer, 1854 p.

Warren, J. K., 2017, Salt usually seals, but sometimes leaks: Implications for mine and cavern stabilities in the short and long term: Earth-Science Reviews, v. 165, p. 302-341.

Warren, J. K., A. Cheung, and I. Cartwright, 2011, Organic Geochemical, Isotopic and Seismic Indicators of Fluid Flow in Pressurized Growth Anticlines and Mud Volcanoes in Modern Deepwater Slope and Rise Sediments of Offshore Brunei Darussalam; Implications for hydrocarbon exploration in other mud and salt diapir provinces (Chapter 10), in L. J. Wood, ed., Shale Tectonics, v. 93: Tulsa OK, AAPG Memoir 93 (Proceedings of Hedberg Conference), p. 163-196.

Zimbelman, D. R., R. O. Rye, and G. N. Breit, 2005, Origin of secondary sulfate minerals on active andesitic stratovolcanoes: Chemical Geology, v. 215, p. 37-60.

 

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mass die-back Evaporite-source rock association Great Salt Lake hydrogen Dead Sea karst collapse auto-suture chert bedded potash evaporite karst 13C Clayton Valley playa: MgSO4 enriched sepiolite wireline log interpretation GR log lazurite tachyhydrite McArthur River Pb-Zn potash mine stability astrakanite natural geohazard 18O sedimentary copper basinwide evaporite Proterozoic HYC Pb-Zn gassy salt Red Sea Messinian dark salt Seepiophila jonesi SedEx Paleoproterozoic Oxygenation Event salt mine sodium silicate palygorskite Hyperarid marine brine sulfur Hell Kettle magadiite Zabuye Lake 18O enrichment halotolerant brine pan solikamsk 2 Karabogazgol Koppen climate lithium brine evaporite Belle Plain Member Stebnyk potash base metal stevensite sulphate subsidence basin deep seafloor hypersaline anoxic basin Five Island salt dome trend lithium battery Mulhouse Basin perchlorate mummifiction water in modern-day Mars hydrothermal karst Danakhil Depression, Afar High Magadi beds Ingebright Lake gem hydrothermal potash phreatomagmatic explosion supercontinent halite-hosted cave knistersalz venice K2O from Gamma Log epsomite Phaneozoic climate 13C enrichment Dead Sea saltworks mirabilite MgSO4 depleted Pilbara Deep Salar de Atacama vanished evaporite Realmonte potash halite evaporite dissolution H2S Lake Peigneur stable isotope seawater evolution Crescent potash salt seal Archean MOP lithium carbonate evaporite-metal association Belle Isle salt mine Catalayud Lomagundi Event Platform evaporite evaporite-hydrocarbon association Neoproterozoic well blowout methanogenesis carbon oxygen isotope cross plots NaSO4 salts Kalush Potash Schoenite well logs in evaporites York (Whitehall) Mine Magdalen's Road Zaragoza Boulby Mine Stebnik Potash gas in salt Deep seafloor hypersaline anoxic lake anthropogenic potash phreatic explosion Lop Nur cauliflower chert meta-evaporite Musley potash brine lake edge North Pole seal capacity Ethiopia water on Mars Sumo saline clay Dallol saltpan collapse doline Dead Sea caves Ripon Turkmenistan intrasalt nitrogen salt leakage, dihedral angle, halite, halokinesis, salt flow, Koeppen Climate DHAB Precambrian evaporites circum-Atlantic Salt Basins kainitite Lamellibrachia luymesi Weeks Island salt mine climate control on salt rockburst Calyptogena ponderosa recurring slope lines (RSL) anomalous salt zones potash ore sulfate eolian transport halophile DHAL lot's wife oil gusher MVT deposit Badenian organic matter Patience Lake member flowing salt sinjarite SOP salt periphery ancient climate doline Density log antarcticite African rift valley lakes Thiotrphic symbionts sinkhole vadose zone Corocoro copper potash ore price brine evolution Ure Terrace salt ablation breccia Quaternary climate salt trade dissolution collapse doline halokinetic hectorite bischofite methanotrophic symbionts salt tectonics sulphur capillary zone Sulphate of potash Mega-monsoon cryogenic salt Prairie Evaporite black salt methane gas outburst zeolite Hadley cell: lapis lazuli Muriate of potash Bathymodiolus childressi extrasalt Lake Magadi carbon cycle nuclear waste storage crocodile skin chert namakier CO2 NPHI log Lop Nor dihedral angle CO2: albedo alkaline lake intersalt source rock salt suture authigenic silica vestimentiferan siboglinids Jefferson Island salt mine freefight lake hydrological indicator anthropogenically enhanced salt dissolution solar concentrator pans CaCl2 brine Pangaea nacholite blowout hydrohalite waste storage in salt cavity snake-skin chert salt karst deep meteoric potash Gamma log allo-suture Kara bogaz gol causes of glaciation geohazard Mesoproterozoic RHOB gypsum dune carnallitite Neoproterozoic Oxygenation Event silica solubility jadarite Atlantis II Deep trona lunette Warrawoona Group silicified anhydrite nodules Neutron Log well log interpretation endosymbiosis

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