Canadian Journal of Earth Sciences
Chlorine isotopes unravel conditions of formation of the Neoproterozoic rock salts from the Salt Range Formation, Pakistan
Journal: Canadian Journal of Earth Sciences
Manuscript ID cjes-2019-0149.R1
Manuscript Type: Article
Date Submitted by the 25-Nov-2019 Author:
Complete List of Authors: Hussain, Syed; CAS ISL, Han, Feng; CAS ISL Han, jibin; CAS ISL Khan, Hawas;Draft Karakoram International University, Department of Earth Sciences Widory, David; Université du Québec à Montréal, Centre GEOTOP
Keyword: Halite, Neoproterozoic, Sylvite, δ37Cl, The Salt Range Formation
Is the invited manuscript for consideration in a Special Not applicable (regular submission) Issue? :
https://mc06.manuscriptcentral.com/cjes-pubs Page 1 of 31 Canadian Journal of Earth Sciences
1 Chlorine isotopes unravel conditions of formation of the Neoproterozoic rock salts from the
2 Salt Range Formation, Pakistan
3 Syed Asim Hussain1, 2, 3,*, Han Feng-qing1, 2, Han Hibin1, 2, Hawas Khan4, David Widory5
4 1) Key Laboratory of Comprehensive and Highly Efficient Utilization of Salt lake Resources, Qinghai Institute of 5 Salt lakes, Chinese Academy of Science, , Xining,810008, China 6 2) Qinghai Provincial Key Laboratory of Geology and Environment of Salt lakes, Xining, China, 810008 7 3) University of Chinese Academy of Science, Beijing, China, 100049 8 4) Department of Earth Sciences, Karakoram International University, 15100, Gilgit, Pakistan. 9 5) GEOTOP/Earth and Atmosphere Sciences Department, UQAM, Montréal, Canada 10 *corresponding author’s E-mail addresses: [email protected] 11
12 Abstract
13 During the late Neoproterozoic,Draft the Salt Range in Pakistan was one of the regions where 14 the Tethys truncated and marine strata developed. The numerous transgressions and regressions
15 that occurred during that period provided enough initial material for the development of marine
16 evaporites. The geology of the Salt Range is characterized by the presence of dense salt layers and
17 the existence of four regional and local scale unconformities. These thick salt deposits geologically
18 favor potash formation. Here we coupled chloride isotope geochemistry and classical chemistry of
19 local halite samples in order to assess the extent of brine evaporation that ultimately formed the
20 salt deposits. Our results indicate that evaporites in the Salt Range area are Br-rich and precipitated
21 from seawater under arid climate conditions. The corresponding δ37Cl values vary from -1.04 to
22 +1.07‰, with an average of -0.25±0.52‰, consistent with the isotope range values reported for
23 other evaporites worldwide. The positive δ37Cl values we obtained indicate the addition of non-
24 marine Cl, may be from reworking of older evaporites, the influx of dilute seawater, the mixing of
25 meteoric and seawater, and the influence of gypsum-dehydration water. The negative Cl isotope
26 compositions (δ37Cl <-1‰) indicate that brines reached the last stages of salt deposition during the
https://mc06.manuscriptcentral.com/cjes-pubs Canadian Journal of Earth Sciences Page 2 of 31
27 Late Neoproterozoic. We conclude that the Salt Range Formation could be promising for K-Mg
28 salts.
29 Keywords: Halite; Neoproterozoic; Sylvite; δ37Cl; The Salt Range Formation
30
31
32
33
34
35 Draft
36
37
38
39
40
41
42
43
44
45
https://mc06.manuscriptcentral.com/cjes-pubs Page 3 of 31 Canadian Journal of Earth Sciences
46 1. Introduction
47 Chlorine (Cl) is an ubiquitous element associated with numerous geochemical processes
48 (Luo et al. 2012). Its uncommon geochemical properties include: highly solubility in water, no
49 bonding to most silicates, and it is usually a trace and incompatible element in nature (Sharp and
50 Draper, 2013). Cl is one of the most abundant elements in many geofluids and one of the major
51 volatile constituents on Earth (e.g. Bureau et al., 2000; Bonifacie et al., 2008). Its global surface
52 average abundance is ~0.5% (Nakamura et al., 2009). Magenheim et al. (1995) estimated that
53 approximately 60% of the Earth Cl is contained within the mantle with the remaining 40% stored
54 in crustal reservoirs (Banks et al., 2000). Studies have shown that Cl is enriched in crustal materials 55 with crustal rocks averaging ~170 ppmDraft of Cl (Rieder et al., 2004). As Cl is evaporative, 56 incompatible (throughout silicates melting) and water soluble, geological processes such as partial
57 melting, magma degassing, hydrothermal activities and weathering concentrate Cl at the Earth
58 surface. In particular, Cl is highly concentrated in marine water (seawater has a Cl concentration
59 of ~20 g/L; Peterson, 2007), saline minerals and terrestrial brines (Bonifacie et al., 2008).
60 Cl has two stable isotopes, 37Cl and 35Cl, whose relative abundances are 24.24:75.76 in
61 nature, respectively (Laeter et al., 2003; Laube, 2010). Due to their relatively large mass difference
62 (5.7%) chlorine stable isotopes display measurable isotope fractionations in the different
63 geological reservoirs (e.g. Tan et al., 2009). For example, salt deposits and saline hydrothermal
64 springs tend to be enriched in 37Cl with respect to seawater (e.g. Kaufmann, 1984). Studies have
65 shown that evaporation and formation of salt minerals favor the heavy 37Cl isotope in the salt
66 deposits with surface reservoirs (evaporites, brines and the oceans) yielding an average δ37Cl of
67 0.05±0.5‰ (e.g. Eggenkamp et al., 1995; Godon et al., 2004; Eastoe et al., 2007). Brines from
68 salt lakes show a δ37Cl range from -2.05 to +1.01‰ or slightly higher (e.g. Liu, 1997; Luo et al.,
https://mc06.manuscriptcentral.com/cjes-pubs Canadian Journal of Earth Sciences Page 4 of 31
69 2012). Most of the physical processes induce Cl isotope fractionation, among which ion filtration
70 (=1.001 to 1.006; Phillips and Bentley, 1987; Agrinier et., 2019), salt precipitation (=1.00055
71 at 28°C; Luo et al., 2012), ion-exchange (=1.0003±0.00006 at 25°C; Musashi et al., 2004) and
72 diffusion (=1.00192±0.00015 at 80°C; Eggenkamp and Coleman, 2009; Du et al., 2016) are
73 inducing the largest chlorine isotope fractionations. Over their history, the Earth’s Cl reservoirs
74 have shown a δ37Cl consistency around the marine water value of 0‰ (Sharp et al., 2007) with
75 most of Cl-rich samples having their δ37Cl nearing this isotope composition (e.g. Eastoe et
76 al.,2007; Bonifacie et al., 2008). One of the most intriguing properties of chlorine isotope
77 compositions is that they can be used to evaluate the evaporation rate at the time of salt formation
78 (Luo et al., 2016). They can thus be used as tracers for characterizing the formation of potash and
79 Mg-salts. Draft
80 The Neoproterozoic period is geologically significant as it has widely been studied for
81 characterizing a large number of geologic processes: e.g. supercontinents collisions and their
82 movements and subduction (Bowring et al., 2007); volcanism (Allen, 2007) high sedimentation
83 rates (Kaufman and Knoll, 1995); evaporite formation and the characterization of paleoclimate
84 environments (Warren, 1999 and 2010). The investigation of ancient evaporative systems is one
85 of the best tools to study local tectonics, basin sedimentation, oxic or anoxic redox and marine or
86 non-marine conditions (Farooqi et al., 2019). The Salt Range (SR) Formation (Fig. 1), an ancient
87 evaporite in Pakistan, deposited during the late Neoproterozoic/Early Cambrian period and is
88 considered the southern border of the western Himalaya (Ghazi et al., 2015), an active frontal
89 thrust zone of the Himalaya in Pakistan (Baker et al., 1988, Iaremchuk et al., 2017). It results of a
90 tectonic collision between the Indian and the Eurasian plates (Grelaud et al., 2002). The distinct
91 features of the SR are i) its dense salt layers, ii) the existence of four regional and local scale
https://mc06.manuscriptcentral.com/cjes-pubs Page 5 of 31 Canadian Journal of Earth Sciences
92 unconformities (Fig. 2A) of Precambrian to Pleistocene ages (Gee and Gee, 1989), and iii) its
93 Permian-Triassic marine belt. For these reasons, the area has been studied for more than a century
94 by geologists and paleontologists, mostly focusing on its tectonics, geological structure,
95 paleontology and petroleum potential but, to our knowledge, there is only a few studies about its
96 geochemistry.
97 With that in mind we carried out this work aiming at the following objectives: (1) to
98 precisely characterize the Cl isotope behavior in halite samples from the Salt Range formation in
99 order to (2) constrain the brine evaporation stages and ultimately (3) to assess the regional potential
100 for potash deposits. 101 2. Geological settings Draft 102 The Salt Range (32°15′–33°0′ N and 71°34′–73°45′ E ) is located in northern Pakistan between
103 the Main Himalayan Fold-Thrust (MHFT) in south and the Main Boundary Trust (MBT) towards
104 north (Fig. 1). It represents the youngest frontal fold and thrust belt with an age of about 67 Ma,
105 which occurred in the advanced stages of the Himalayan orogeny (Powell et al., 1988). The
106 existence of the thick, incompetent SR Fm. at the base of the sedimentary sequence has greatly
107 affected the regional geology and structure (Gee and Gee, 1989). Due to the existence of the
108 evaporitic SR Formation the deformation style of the Potwar Basin is distinct between its southern
109 and northern parts (Lillie et al., 1987; Richards et al., 2015). The SR presents a complicated salt
110 anticlinorium with a chain of salt anticlines, having its maximum thickness in its central part
111 (Farooqi et al., 2019). Fatimi (1973) evaluated the thickness of the SR Fm. between 800 and 2000
112 m. The SR itself emerged following the movement of the Potwar Plateau towards south, supported
113 by an E-W striking and down to the north basement normal fault (Richards et al., 2015).
114 Stratigraphically, the SR displays from the Neoproterozoic to Paleogene rocks of the SR Fm.
https://mc06.manuscriptcentral.com/cjes-pubs Canadian Journal of Earth Sciences Page 6 of 31
115 (Jhelum, Nilawahan and Chharat groups) up to the Eocene (Fig. 2). The overall exposed strata is
116 fairly complete in the SR. Rocks older than the Eocambrian are generally not exposed but a few
117 outcrops can be found in the Kirana and Sangla hills of the Punjab plains (southeast of the SR;
118 Krishnan et al., 1966). Gee and Gee (1989) divided the SR into three main sections: i) The Eastern
119 SR (from Jogi Tilla to Khewra), ii) the Central SR (from Khewra to Warchha) and iii) the Western
120 SR (from Sakesar to Kalabagh). The SR is wider in its middle section (between Khewra and
121 Warchha) where it makes up for one of the best successions of the Eocambrian period.
122 The SR Formation is mainly formed of halite, anhydrite, dolomite, gypsum that may extend
123 up to the Hazara District (Latif, 1970). Combined with the coeval similarly restricted marine 124 deposits of the Ara Formation in Oman,Draft the Hurmuz Formation in Iran, and the salt deposits in 125 India, it suggests a widespread evaporite deposition across this area (Smith, 2012). Within the SR
126 area, the SR Formation is divided into three members, based on their location and occurrence: i)
127 the Billianwala Salt Member, ii) the Bandarkas Gypsum Member and iii) the Sahwal Marl Member
128 (Fig. 2A). These three units outcrop in the Khewra Gorge (Fig. 1). The Billianwala Salt Member
129 incorporates marl, thick seams of halite and potash seams. The Bandarkas Gypsum Member
130 displays marl with important deposits of gypsum that range from crystalline to non-crystalline.
131 The Sahwal Marl Member consists of marl and thick seams of halite (~2-4m). The Billianwala
132 Salt Member is observed in the Khewra salt mine and is divided into seven seams, three in the
133 upper group called the Buggy complex and four in the lower group called the Pharwala complex
134 (Fig. 2C). The Khewra area is an asymmetrical dome cut by the Khewra stream that exposes a
135 significant stratigraphic part of this area. A complete sequence of the SR Fm. is exposed about one
136 km from the mouth of the Khewra salt mine (Table 1). All exposed strata in the Khewra salt mines
https://mc06.manuscriptcentral.com/cjes-pubs Page 7 of 31 Canadian Journal of Earth Sciences
137 are part of the lower or main saline marls. Faults in their southern and western parts limit the main
138 mine extension.
139 3. Material and methods
140 1.1 Sampling strategy
141 We collected a total of 28 halite samples in the Kherawa salt mine (Salt Range Formation;
142 Fig. 2). Details about the sample locations are reported in Table 2. Fresh halite samples were
143 collected in order to obtain the most representative samples and to avoid any potential bias
144 resulting from secondary processes.
145 3.2 Elemental concentrations
Draft+ + 2+ 3+ 2+ 2- - - - 146 For each sample, we determined K , Na , Ca , B , Mg , SO4 , Br , Cl , NO3
147 concentrations and corresponding Cl stable isotope compositions (δ37Cl). K+, Ca2+, Mg2+, and B3+
148 concentrations were measured by ICP-OES (ICAP6500DUO, USA) with a precision better than
- - 2- 149 5%. Br , NO3 and SO4 were analyzed by Ion Chromatography (IC-5000+, Thermo Fisher USA)
150 and Cl- was measured by chemical mercurimetry, with an accuracy higher than 0.3% (ISL, CAS,
151 1988). δ37Cl was analyzed using high-accuracy Positive Thermal Ionization Mass Spectrometry
152 (TIMS-TRITON, U.S.A) with a detection limit of 1-320 a.m.u. All measurements were made at
153 the Salt Lakes Analytical and Testing Department, Qinghai Institute of Salt Lakes, Chinese
154 Academy of Sciences.
155 3.3 Chlorine isotope compositions analysis
156 All halite samples were dissolved in pure (at least 4 times deionized) water. The ensuing
157 purification process followed the two-steps resin method described by Xiao et al. (1995). Briefly,
158 a polyethylene ion-exchange column (diameter of 0.5 cm) was filled with 2 cm of a reborn H-
https://mc06.manuscriptcentral.com/cjes-pubs Canadian Journal of Earth Sciences Page 8 of 31
159 cation exchange resin (200-400 mesh, resin type: Dowex 50WX8). Then, 1.6 cm of regenerated
160 Cs-cation exchange resin was inserted into a second polyethylene ion-exchange column (diameter
161 of 0.4 cm). Samples were first eluted through the H-cation exchange resin column and then through
162 the Cs one. During the process, the pH of the solution was maintained between 3 and 6, without
2- - 163 the aid of a buffer solution. Ultimately, samples were collected for TIMS analysis. As SO4 /Cl
- - 164 and NO3 /Cl molar ratios were all below 2.5 and 0.5 in our samples, respectively, no further
2- - 165 purification was needed as interferences by SO4 and NO3 can then be considered as negligible
166 (Luo et al., 2016). Here, we used NaCl (ISL-354 NaCl) as the Cl isotope standard reference
167 material. This seawater standard was collected at coordinates 4018/ N, 101008/ E and is considered
168 the Standard Mean Ocean Chloride (SMOC) (Xiao et al., 2002). Draft 169 For Cl isotope analysis, solutions were prepared to ultimately contain approximatively 5 mg/ml
170 Cl. A tantalum (Ta) filament was heated under vacuum for one hour (using a current of 2-3A)
171 before being covered with 2.5 µL of a graphite slurry that contained at least 80% of ethanol plus
172 80 µg of graphite. About 2.5 µL of the sample solution, containing at least 10 µg of Cl as CsCl
173 was deposited onto the filament, which was then dried using a current of 1A for <3 minutes.
174 Samples were finally placed into the source of the TIMS mass spectrometer until a vacuum of
-7 + - 175 around 2.5×10 mbars was reached. During the analysis, the Cs2Cl ion current was kept at 4 ×10
176 12 A by adjusting the TIMS source current. Data were simultaneously collected on Faraday cup
133 35 + 133 37 + 177 “C” and “H1” by using the ion flows from mass numbers 301 ( Cs2 Cl ) and 303 ( Cs2 Cl ).
178 The 37Cl/35Cl ratio we obtained for the international IAEA ISL-354 NaCl standard was
179 0.319028±0.000058 (n=12), in agreement with Hussain et al. (2019) and with the certified value
180 of Xiao et al. (2002) of 0.31964±0.00092. Precision for the 37Cl determination was >±0.3‰.
181 We reported the Cl stable isotope compositions using the classical “δ” (delta) notation:
https://mc06.manuscriptcentral.com/cjes-pubs Page 9 of 31 Canadian Journal of Earth Sciences
37퐶푙 35 퐶푙푠푎푚푝푙푒 182 훿37퐶푙 = ― 1 × 103 (1) 37퐶푙 ⌈35퐶푙 ⌉ 퐼푆퐿 ― 354
183
184 4. Results and discussion
185 The Cl isotope and elemental compositions of our halite samples are given in Table 2.
+ - 2– 186 Results show that Na and Cl are the major ions, followed by SO4 . Additionally, trace elements
187 such as B3+ and Br- are also detected. The δ37C1 of the halite samples range from -1.04 to +1.07‰
188 with an average value of -0.25±0.52‰. Most of the Cl isotope compositions fall between -0.5 and 189 +0.5‰. Draft 190 4.1 Origin of the halite
191 Geochemistry has been widely used to identify the sources of salts (e.g. Schreiber and
192 Tabakh, 2000), discriminating them into three distinct types: terrigenous, hydrothermal and marine
193 (e.g. Guo et al., 2017). Previous studies suggested that there is no evidence of evaporite
194 precipitation from non-marine or continental brines in the SR (e.g. Hardie, 1984). Hydrothermal
195 fluids migrating along the deep large faults are also improbable sources for these salts as: (1) the
196 δ37Cl we measured in the SR hydrothermal waters (about ±1‰) are distinct from those reported
197 worldwide, ranging from negative isotope compositions to as high as +3‰ (Guo et al., 2017). (2)
198 Hydrothermal depositions are usually accompanied by extremely high Mn and Fe concentrations
199 (Hardie, 1990). For the SR, their concentrations are on average extremely low, 0.06 and 0.97 ppm,
200 respectively (Sharif et al., 2007). But ultimately these two elements may be controlled by the pH
201 of the fluids as well as the presence of complexating anions such as Cl- and F-. (3) Kovalevych et
https://mc06.manuscriptcentral.com/cjes-pubs Canadian Journal of Earth Sciences Page 10 of 31
202 al. (2006) reported an approximate homogenization temperature of the saline inclusions in the
203 halite of 50-1000C, which contradicts a deep hydrothermal origin.
204 The lithology of the SR Formation indicates a marine nature: at an earlier stage, it had been
205 isolated from the main Tethys Sea during a regression event that ultimately formed a lake (Latif,
206 1970; Ghazi et al., 2015). Its depositional environment is considered as a shallow marine under
207 arid conditions in which evaporite succession developed (Latif 1970; Farooqi et al., 2019). The
208 concentrations we measured for elements such as B and Br (Table 2) also support this marine
209 nature, although most of our Br values are between 50-100 ppm, in the lower range of those
210 reported for halite precipitated from marine water (65–270 ppm; Holser, 1979). These low Br 211 concentrations may result from the reworkingDraft of older evaporites, the influx of dilute seawater, the 212 mixing of meteoric and seawater, and the influence of gypsum-dehydration water (Kovalevych et
213 al., 2006). Eggenkamp et al. (2019) demonstrated that Br is entering less easily the halite
214 crystalline structure compared to Cl, making the impact of this process less significant on the Br
215 concentrations. Shurui et al. (2019) recently hypothesized that Br contents are more useful to
216 reveal the stage of brine evaporation. Still, together, C1 isotope geochemistry of evaporites, their
217 mineralogy and the sedimentological evidences (i.e. depositional environments) confirm that the
218 SR was formed under marine conditions.
219 4.2 Chlorine isotopes and Cl/Br ratios in the halite
220 Sedimentary basins created by evaporated seawater display negative δ37C1 (≤0.0‰;
221 Eggenkamp et al., 1995; Eastoe et al., 2001). This again comforts our conclusion of a marine origin
222 as the δ 37Cl we obtained for 6 of the 8 salt seams (Fig. 1) are strictly negative, ranging from -1.04
223 to -0.01‰ (average of -0.46±0.30‰). The other 2 samples, collected in the Buggy and North
https://mc06.manuscriptcentral.com/cjes-pubs Page 11 of 31 Canadian Journal of Earth Sciences
224 Buggy sections, unexpectedly, show positive Cl isotope compositions, from 0.02 to 1.07‰, with
225 an average of 0.53±0.36‰).
226 The Cl/Br ratio is one of the most effective and sensitive indexes when determining the
227 geological environment, the degree of concentration and the depositional phase associated to the
228 brine evaporation process (Han et al., 2019). This ratio is mainly controlled by the sequential
229 formation of salt minerals during the evaporation of marine water, resulting from their possible
230 substitution, having similar ion radii. The average Cl/Br (molar) ratio of present seawater is ~300
231 and has remained constant through geological history (Kaufmann 1999a; Sakellariou-
232 Makrantonakie, 2008; Yechieli, 2009). While seawater evaporation increases Br concentrations, 233 dilution will decrease them (Han, et al.,Draft 2018). The Cl/Br ratio of evaporated seawater remains 234 constant until halite starts precipitating at a NaCl concentration near 6.2 mol/L (Alcala and
235 Custodio, 2008). During the evaporation process the first minerals formed are Ca salts, followed
236 by SO4 salts, NaCl (Halite), KCl (Sylvite), KMgCl.6H2O (Carnallite) and finally MgCl2.6H2O
237 (Bischofite) (Warren, 2010 and references therein). In general, the later evaporation phases induce
238 a Br- depletion (Wilson and Long, 1993). In our study, the Cl/Br ratios ranged between 1.32×103
239 to 8.47×103, in agreement with the 103-105 ratios generally considered for NaCl minerals
240 (Kloppmann et al., 2001; Cartwright et al., 2006).
241 The relationships existing between Cl/Br and δ37Cl in Figure 3 give information about the
242 halite dissolution or recrystallization processes. Previous studies have proved that dissolution and
243 recrystallization do not affect both Cl/Br and δ 37Cl (e.g. Banks et al., 2000), but if continental
244 waters are mixed with brine before evaporation occurs, the Cl/Br ratio of the solution will be
245 distinct from that of the seawater (Han et al., 2019). Here, all Cl/Br ratios are very high compared
246 to the ~300 seawater (Fig. 3), indicating that in the SR seawater was mixed with continental water
https://mc06.manuscriptcentral.com/cjes-pubs Canadian Journal of Earth Sciences Page 12 of 31
247 and/or that water-rock interaction (WRI; Farooqi et al., 2019) occurred. Figure 4 reports the
248 classical Na/Br vs Cl/Br diagram. When seawater undergoes evaporation and crystallization, Br
249 will preferentially concentrate in the remaining seawater, resulting from its difficulty to enter the
250 halite mineral lattice (e.g. Liu et al., 2016). This results in a decrease of the corresponding Na/Br
251 and Cl/Br molar ratios in the residual seawater (e.g. Liu et al., 2016). On the other hand, brines,
252 formed by dissolution of precipitated halite by fresh water, yield higher Na/Br and Cl/Br molar
253 ratios compared to seawater (e.g. Liu et al., 2016). When plotted into the diagram (Figure 4), the
254 ratios that we obtained for our halite samples also hint at multiple sources for the halite as well as
255 the occurrence of recrystallization and WRI. Moreover, all samples plot above the seawater halite
256 precipitation line defined by Kesler et al. (1995), again indicating multiple WRI processes that
257 explain that all our Na/Br and Cl/Br ratiosDraft are greater than those of seawater (Fig. 4).
258 δ37C1 variations in the halite samples are slightly larger than those reported from other
259 sedimentary basins (0.0±0.9‰: Eastoe et al., 1999). This also confirms that, beside a high
260 evaporation rate, continental/non-marine waters influenced the salt formation (e.g. Xiao et al,
261 2000). The evaporation process concentrates brines and continuously decreases the corresponding
262 37Cl (e.g. Luo et al., 2014). Here, as reported for other sedimentary basins (e.g. Tan et al. 2005),
263 the δ37C1 of the potash seam are more negative than those of common salt (Table 2), consistent
264 with previous laboratory experiments (Eastoe et al., 2007).
265 4.3 Inputs of non-Marine Chloride
266 Evaporites forming in basins having no or limited connections with the open sea are expected
267 to episodically get waters and solutes from non-marine sources (Hardie, 1984). Previous studies
268 have shown that the geology deposition cycle in the SR begins with marine evaporite facies,
269 followed by an irregular marine and non-marine sedimentation sequence and finally settled with a
https://mc06.manuscriptcentral.com/cjes-pubs Page 13 of 31 Canadian Journal of Earth Sciences
270 second evaporite facies, i.e. recrystallization (Ghauri, 1979; Kovalevych et al., 2006). In an
271 evaporite basin, the input of non-marine Cl may depend on its shape and geometry (Warren, 1999).
272 As thus, smaller basins, like the Salt Range, are more susceptible to yield δ37C1 significantly
273 distinct from the ones of the corresponding marine waters, as a consequence of those non-marine
274 contributions. Since the SR Fm. is a remnant of the Tethys Sea (Latif, 1970; Ghazi et al., 2015)
275 and chemically demonstrates a marine origin (see section 4.1), the corresponding δ37Cl should be
276 centered around 0±0.5‰ (Eatoe et al., 2001 and 2007). Here, our results show that the 37Cl of the
277 SR halite samples can be separated into two different families (Figure 3): 1) Samples that with the
278 low 37Cl that show a high concentration of ancient brines, i.e. they reached the late phase of
279 deposition. 2) The samples with the positive δ37Cl that indicate that the brines have either been
280 mixed with non-marine Cl (e.g. EastoeDraft et al., 2007; Farooqi et al., 2019) and/or underwent
281 recrystallization (Kovalevych et al. 2006; Warren, 2016), that resulted in chlorine isotope
282 compositions distinct from the marine evaporites.
283 4.4 Economical deposits and δ37C1
284 Luo et al. (2012, 2014) experimentally proposed that 37Cl constantly decrease during the
285 initial phase of brine deposition. Consequently, when the halite precipitates during the late
286 deposition phase, it yields more negative 37Cl. This 37Cl-depletion continues until the
287 crystallization of K-Mg salts (Luo et al., 2016). Hence, the study of the Cl isotope compositions
288 gives information on the evaporation stage, and thus changes in the 37Cl can be related to the
289 evaporation cycles of saline lakes.
290 Most of our 37Cl are within the range of 0 to -0.5‰ with some values below, which indicates
291 that during salt deposition the evaporation rate was high in the SR area. Reported δ37Cl values for
https://mc06.manuscriptcentral.com/cjes-pubs Canadian Journal of Earth Sciences Page 14 of 31
292 salt deposits worldwide are usually ≤-0.60‰ for K-salts and <-1‰ for carnallite (Table 3). Our
293 study therefore shows that the Salt Range Formation was developed in the later stage of brine
294 deposition, which is promising in terms of potential for sylvinite and carnallite deposits, in
295 agreement with previous geological studies (Table 2 & 3).
296 4.5 Comparison of the Cl isotope compositions of the Salt Range with other basins
297 It has now been well documented that the Cl stable isotope compositions of terrestrial
298 reservoirs are distinct from the δ37C1 of present-day seawater (Guo et al., 2017; Figure 5): δ37C1
299 around 0‰ are representative of a marine source; terrestrial materials such as basalt (MORB) show
300 highly enriched δ37C1 (7- 8‰; Sharp et al., 2007) and waters from subduction zones have δ37C1 301 around -7.5 ‰ (Ransom et al., 1995; WeiDraft et al., 2008). K-forming basins have δ37C1 ranging from 302 0 to ±1‰ (Tan et al., 2005; Eastoe et al., 2007), isotope compositions varying with the tectonic
303 settings, the Cl sources and the formation environment. Eastoe et al. (2007) reported a -1 to +1‰
304 range for chlorine isotope compositions of K-salts during the study of halite samples from 5
305 different basins. Tan et al. (2005) reported δ37C1 of -2.41 and 0.44‰ for the Navarra and Catalonia
306 Basins (Spain), respectively, while the sylvite from the Mahai Salt Lake (China) was about -0.90‰
307 (Table 3). In the Salt Range the δ37C1values range between -1.04 to +1.07‰, similar to the Mahai
308 Salt Lake (China), the Khorat Basin (Thailand) and the Nepa Basin (Russia) (Table 3). These data
309 indicate that most of the δ37C1 for Mg-K salts lay between -1 and +1‰, confirming that the SR
310 formation is promising for economical K and Mg salts deposits (Figure 5). The proven reserves
311 though are mainly located in the Khewra mine (Figure 1C), but their extraction is rendered difficult
312 due to the fact that gravity (Ahmad et al., 1979) and airborne (OGDCL, 1962, 1963: Drewes et al.,
313 2007) studies have shown that they are situated at shallow depths.
314 5. Conclusions
https://mc06.manuscriptcentral.com/cjes-pubs Page 15 of 31 Canadian Journal of Earth Sciences
315 1) The thick bedded halite in the Salt Range formation is strongly associated to its marine
316 source, demonstrated by the range of their δ37C1, from -1.04 to +1.07‰ (average of -
317 0.25±0.52‰)
318 2) δ 37Cl of the salt rock samples show two dissimilar patterns. Of the eight seams studied,
319 six yielded negative isotope compositions and the other two positive ones. The overall
320 halite isotope variations are slightly larger than the marine water Cl (δ37C1 = 0.0‰). This
321 is explained by the input of non-marine Cl and incongruent solution (which results in the
322 partitioning of Br into saturated NaCl solution, inducing a Cl isotope fractionation; Eastoe
323 et al., 2001). The Potash seam shows lower δ37C1, which is consistent with values
324 previously reported for i) other basins (Tan et al., 2005 reported 37Cl <0.33‰ for salts
325 collected above and below potashDraft strata, <-0.6‰ in sylvite, and <-1‰ for carnallite) and
326 ii) laboratory experiments (e.g. -0.9<37Cl<0‰; Eastoe et al, 1999; Luo et al., 2014).
327 3) The δ37C1 presented here, in conjunction with previous geological studies, suggest that the
328 salts have reached their final stage of precipitation and possibly the stability fields of K-
329 salts. This indicates that the SR area is favorable for sylvite deposits.
330 4) To date, the characterization of the δ37C1 isotope compositions of the Salt Range area is
331 still scarce rending the predictions of the exact salt precipitation stage very difficult.
332 Further studies, comparing δ37C1 with those of known sylvite deposits, particularly with
333 evaporite basins of similar origins (e.g. India, Iran and Oman) are needed to more precisely
334 outline the terminal stages of the brines.
335
336
https://mc06.manuscriptcentral.com/cjes-pubs Canadian Journal of Earth Sciences Page 16 of 31
337 References
338 Agrinier, P., Destrigneville, C., Giunta, T., Bonifacie, M., Bardoux, G., Andre, J., Lucazeau, F.
339 2019. Strong impact of ion filtration on the isotopic composition of chlorine in young clay-
340 rich oceanic sediment pore fluids. Geochimica et Cosmochimica Acta, 245: 525-541.
341 Ahmad, M.A., Rahim, S.M., Mirza, M.A., Sakhawat, Muhammad, Ahmad, Khursheed, and Farah,
342 Abul. 1979. Seismic refraction traverses near Khewra salt deposits, Jhelum District,
343 Punjab, Pakistan: Geological Survey of Pakistan Information Release 110 :13.
344 Alcalá, F.J., and Custodio, E. 2008. Using the Cl/Br ratio as a tracer to identify the origin of salinity
345 in aquifers in Spain and Portugal. Journal of Hydrology, 359: 189-207.
346 Allen, P.A. 2007. The Huqf Supergroup of Oman: basin development and context for 347 Neoproterozoic glaciation. Earth-ScienceDraft Reviews, 84: 139-185. 348 Baker, D.M., Lillie, R.J., Yeats, R.S., Johnson, G.D., Yousuf, M., and Zamin, A.S.H. 1988.
349 Development of the Himalayan frontal thrust zone: Salt Range, Pakistan. Geology, 16: 3-
350 7.
351 Banks, D., Green, R., Cliff, R., and Yardley, B. 2000. Chlorine isotopes in fluid inclusions:
352 determination of the origins of salinity in magmatic fluids. Geochimica et Cosmochimica
353 Acta, 64: 1785-1789.
354 Bonifacie, M., Jendrzejewski, N., Agrinier, P., Humler, E., Coleman, M., and Javoy, M. 2008. The
355 chlorine isotope composition of Earth's mantle. Science, 319: 1518-1520.
356 Bowring, S.A., Grotzinger, J.P., Condon, D.J., Ramezani, J., Newall, M.J., and Allen, P.A. 2007.
357 Geochronologic constraints on the chronostratigraphic framework of the Neoproterozoic
358 Huqf Supergroup, Sultanate of Oman. American Journal of Science, 307: 1097-1145.
359 Bureau, H., Keppler, H., and Métrich, N. 2000. Volcanic degassing of bromine and iodine:
360 experimental fluid/melt partitioning data and applications to stratospheric chemistry. Earth
https://mc06.manuscriptcentral.com/cjes-pubs Page 17 of 31 Canadian Journal of Earth Sciences
361 and Planetary Science Letters, 183: 51-60.
362 Cartwright, I., Weaver, T.R., and Fifield, L.K. 2006. Cl/Br ratios and environmental isotopes as
363 indicators of recharge variability and groundwater flow: an example from the southeast
364 Murray Basin, Australia. Chemical Geology, 231: 38-56.
365 de Laeter, J.R., Böhlke, J.K., De Bièvre, P., Hidaka, H., Peiser, H., Rosman, K., and Taylor, P.
366 2003. Atomic weights of the elements. Review 2000 (IUPAC Technical Report). Pure and
367 applied chemistry, 75: 683-800.
368 Drewes, H., Ahmad, Z., and Khan, R. 2007. Resource Evaluation of Selected Minerals and
369 Industrial Commodities of the Potwar Plateau Area, Northern Pakistan. Geological
370 Survey (US). No. 2078-H.
371 Eastoe, C., and Peryt, T. 1999. Stable chlorineDraft isotope evidence for non‐marine chloride in
372 Badenian evaporites, Carpathian mountain region. Terra Nova, 11: 118-131.
373 Eastoe, C., Long, A., Land, L.S., and Kyle, J.R. 2001. Stable chlorine isotopes in halite and brine
374 from the Gulf Coast Basin: brine genesis and evolution. Chemical Geology, 176: 343-360.
375 Eastoe, C., Peryt, T., Petrychenko, Y., and Geisler-Cussey, D. 2007. Stable chlorine isotopes in
376 Phanerozoic evaporites. Applied Geochemistry, 22: 575-588.
377 Eggenkamp, H., and Schuiling, R. 1995. δ37C1 variations in selected minerals: a possible tool for
378 exploration. Journal of Geochemical Exploration, 55: 249-255.
379 Eggenkamp, H., and Coleman, M.L. 2009. The effect of aqueous diffusion on the fractionation of
380 chlorine and bromine stable isotopes. Geochimica et Cosmochimica Acta, 73: 3539-3548.
381 Eggenkamp, H., Kreulen, R., and Van Groos, A.K. 1995. Chlorine stable isotope fractionation in
382 evaporites. Geochimica et Cosmochimica Acta, 59: 5169-5175.
383 Farooqui, M.A., Umar, M., Sabir, M.A., Pervez, R., and Jalees, T. 2019. Geochemical attributes
https://mc06.manuscriptcentral.com/cjes-pubs Canadian Journal of Earth Sciences Page 18 of 31
384 of late Neoproterozoic Salt Range Formation, Pakistan: constraints on provenance,
385 paleoclimate, depositional and tectonic settings. Geosciences Journal, 23: 201-218.
386 Fatmi, A.N. 1974. Lithostratigraphic units of the Kohat-Potwar province, Indus basin, Pakistan.
387 Mem. Geol. Surv. Pakistan, 10: 1-80.
388 Gee, E., and Gee, D. 1989. Overview of the geology and structure of the Salt Range, with
389 observations on related areas of northern Pakistan. Geological Society of America Special
390 Paper, 232: 95-112.
391 Ghauri, A.A.K. 1979. Sedimentary Structures Of the Jutana Dolomite And The Baghanwala
392 Formation. Journal of Himalayan Earth Sciences, 12.
393 Ghazi, S., Ali, S.H., Sahraeyan, M., and Hanif, T. 2015. An overview of tectonosedimentary
394 framework of the Salt Range, Draft northwestern Himalayan fold and thrust belt, Pakistan.
395 Arabian Journal of Geosciences, 8: 1635-1651.
396 Godon, A., Jendrzejewski, N., Eggenkamp, H.G., Banks, D.A., Ader, M., Coleman, M.L., and
397 Pineau, F. 2004. A cross-calibration of chlorine isotopic measurements and suitability of
398 seawater as the international reference material. Chemical Geology, 207: 1-12.
399 Grelaud, S., Sassi, W., de Lamotte, D.F., Jaswal, T., and Roure, F. 2002. Kinematics of eastern
400 Salt Range and South Potwar basin (Pakistan): a new scenario. Marine and Petroleum
401 Geology, 19: 1127-1139.
402 Guo, P., Liu, C., Huang, L., Wang, P., Wang, K., Yuan, H., Xu, C., and Zhang, Y. 2017. Genesis
403 of the late Eocene bedded halite in the Qaidam Basin and its implication for paleoclimate
404 in East Asia. Palaeogeography, Palaeoclimatology, Palaeoecology, 487: 364-380.
405 Han, J.-L., Hussain, S.-A., and Han, F.-Q. 2019. Stable chlorine isotopes in saline springs from
406 the Nangqen basin, Qinghai–Tibet Plateau: Brine genesis and evolution. Journal of earth
https://mc06.manuscriptcentral.com/cjes-pubs Page 19 of 31 Canadian Journal of Earth Sciences
407 system science, 128: 206.
408 Han, J.-l., Han, F.-q., Hussain, S.-A., Liu, W.-y., Nian, X.-q., and Mao, Q.-f. 2018. Origin of Boron
409 and Brine Evolution in Saline Springs in the Nangqen Basin, Southern Tibetan Plateau.
410 Geofluids, 2018.
411 Hardie, L.A. 1984. Evaporites; marine or non-marine? American Journal of Science, 284: 193-
412 240.
413 Hardie, L.A. 1990. The roles of rifting and hydrothermal CaCl 2 brines in the origin of potash
414 evaporites; an hypothesis. American Journal of Science, 290: 43-106.
415 Holser, W. 1979. Trace elements and isotopes in evaporites. In Marine Minerals. Mineralogical
416 Society of America Short Course Notes Washington, DC. pp. 295-346.
417 HongBing, T., HaiZhou, M., XiYing, M.,Draft JianXin, X., and YingKai, X. 2009. Fractionation of
418 chlorine isotope in salt mineral sequences and application: Research on sedimentary stage
419 of ancient salt rock deposit in Tarim Basin and western Qaidam Basin. Acta Petrologica
420 Sinica, 25: 955-962.
421 Hussain, S.A., Han, F.-Q., Han, W., Rodríguez, A., Han, J.-L., Han, J., Nian, X.-Q., Yi, L., Ma,
422 Z., and Widory, D. 2019. Climate Change Impact on the Evolution of the Saline Lakes of
423 the Soan-Sakaser Valley (Central Salt Range; Pakistan): Evidences from Hydrochemistry
424 and Water (δD, δ18O) and Chlorine (δ37Cl) Stable Isotopes. Water, 11: 912.
425 Iaremchuk, I., Tariq, M., Hryniv, S., Vovnyuk, S., and Meng, F. 2017. Clay minerals from rock
426 salt of Salt Range Formation (Late Neoproterozoic–Early Cambrian, Pakistan). Carbonates
427 and Evaporites, 32: 63-74.
428 Kaufmann, R., Long, A., Bentley, H., and Davis, S. 1984. Natural chlorine isotope variations.
429 Nature, 309: 338.
https://mc06.manuscriptcentral.com/cjes-pubs Canadian Journal of Earth Sciences Page 20 of 31
430 Kloppmann, W., Négrel, P., Casanova, J., Klinge, H., Schelkes, K., and Guerrot, C. 2001. Halite
431 dissolution derived brines in the vicinity of a Permian salt dome (N German Basin).
432 Evidence from boron, strontium, oxygen, and hydrogen isotopes. Geochimica et
433 Cosmochimica Acta, 65: 4087-4101.
434 Kovalevych, V.M., Marshall, T., Peryt, T.M., Petrychenko, Y., and Zhukova, S.A. 2006. Chemical
435 composition of seawater in Neoproterozoic: Results of fluid inclusion study of halite from
436 Salt Range (Pakistan) and Amadeus Basin (Australia). Precambrian Research, 144: 39-51.
437 Krishnan, M. 1966. Salt tectonics in the Punjab salt range, Pakistan. Geological Society of America
438 Bulletin, 77: 115-122.
439 Latif, M. 1970. Explanatory notes on the geology of southeastern Hazara to accompany the revised
440 geological map. Jahrbuch der GeologischenDraft Bundesanstalt, Sonderband, 15: 5-20.
441 Laube, J., Kaiser, J., Sturges, W., Bönisch, H., and Engel, A. 2010. Chlorine isotope fractionation
442 in the stratosphere. Science, 329: 1167-1167.
443 Lillie, R.J., Johnson, G.D., Yousuf, M., Zamin, A.S.H., and Yeats, R.S. 1987. Structural
444 development within the Himalayan foreland fold-and-thrust belt of Pakistan.
445 Liu, W., Xiao, Y., Wang, Q., Qi, H., Wang, Y., Zhou, Y., and Shirodkar, P. 1997. Chlorine isotopic
446 geochemistry of salt lakes in the Qaidam Basin, China. Chemical Geology, 136: 271-279.
447 Liu, J., Chen, Z., Wang, L., Zhang, Y., Li, Z., Xu, J., Peng, Y. 2016. Chemical and isotopic
448 constrains on the origin of brine and saline groundwater in Hetao plain, Inner Mongolia.
449 Environmental Science and Pollution Research, 23: 15003-15014.
450 Luo, C., Xiao, Y., Ma, H., Ma, Y., Zhang, Y., and He, M. 2012. Stable isotope fractionation of
451 chlorine during evaporation of brine from a saline lake. Chinese Science bulletin, 57: 1833-
452 1843.
https://mc06.manuscriptcentral.com/cjes-pubs Page 21 of 31 Canadian Journal of Earth Sciences
453 Luo, C., Xiao, Y., Wen, H., Ma, H., Ma, Y., Zhang, Y., Zhang, Y., and He, M. 2014. Stable isotope
454 fractionation of chlorine during the precipitation of single chloride minerals. Applied
455 Geochemistry, 47: 141-149.
456 Luo, C., Wen, H., Xiao, Y., Ma, H., Fan, Q., Ma, Y., Zhang, Y., Yang, X., and He, M. 2016.
457 Chlorine isotopes in sediments of the Qarhan Playa of China and their paleoclimatic
458 significance. Chemie der Erde-Geochemistry, 76: 149-156.
459 Magenheim, A.J., Spivack, A.J., Michael, P.J., and Gieskes, J.M. 1995. Chlorine stable isotope
460 composition of the oceanic crust: implications for Earth's distribution of chlorine. Earth
461 and Planetary Science Letters, 131: 427-432.
462 Musashi, M., Oi, T., Eggenkamp, H., and Yato, Y. 2004. Experimental Determination of Chlorine
463 Isotope Effect by Ion-exchange Technique.Draft Radioisotopes, 53: 213-218.
464 Nakamura, N., Nyquist, L., Reese, Y., Shih, C., Numata, M., Fujitani, T., and Okano, O. 2009.
465 Chlorine Isotopes: As a Possible Tracer of Fluid/Bio-Activities on Mars and a Progress
466 Report on Chlorine Isotope Analysis by TIMS. NASA-JSC report.
467 Peterson, J., MacDonell, M., Haroun, L., Monette, F., Hildebrand, R.D., and Taboas, A. 2007.
468 Radiological and chemical fact sheets to support health risk analyses for contaminated
469 areas. Argonne National Laboratory Environmental Science Division, 133.
470 Phillips, F.M., and Bentley, H.W. 1987. Isotopic fractionation during ion filtration: I. Theory.
471 Geochimica et Cosmochimica Acta, 51: 683-695.
472 Ransom, B., Spivack, A.J., and Kastner, M. 1995. Stable Cl isotopes in subduction-zone pore
473 waters: Implications for fluid-rock reactions and the cycling of chlorine. Geology, 23: 715-
474 718.
475 Richards, L., King, R., Collins, A., Sayab, M., Khan, M., Haneef, M., Morley, C., and Warren, J.
https://mc06.manuscriptcentral.com/cjes-pubs Canadian Journal of Earth Sciences Page 22 of 31
476 2015. Macrostructures vs microstructures in evaporite detachments: An example from the
477 Salt Range, Pakistan. Journal of Asian Earth Sciences, 113: 922-934.
478 Rieder, R., Gellert, R., Anderson, R., Brückner, J., Clark, B., Dreibus, G., Economou, T.,
479 Klingelhöfer, G., Lugmair, G., and Ming, D. 2004. Chemistry of rocks and soils at
480 Meridiani Planum from the Alpha Particle X-ray Spectrometer. Science, 306: 1746-1749.
481 Sakellariou-Makrantonaki, M., Dimakas, D., and Angelaki, A. Determination of bromide and
482 chloride concentrations in drinking water at Pelion Mountain (Central Greece). In
483 Agricultural and biosystems engineering for a sustainable world. International Conference
484 on Agricultural Engineering, Hersonissos, Crete, Greece, 23-25 June, 2008. 2008.
485 European Society of Agricultural Engineers (AgEng).
486 Schreiber, B.C., and Tabakh, M.E. Draft 2000. Deposition and early alteration of evaporites.
487 Sedimentology, 47: 215-238.
488 Schröder, S., Schreiber, B.C., Amthor, J.E., and Matter, A. 2003. A depositional model for the
489 terminal Neoproterozoic–Early Cambrian Ara Group evaporites in south Oman.
490 Sedimentology, 50: 879-898.
491 Sharif, Q.M., Hussain, M., Hussain, M.T., Ahmad, V., and Raza Shah, M. 2007. Chemical
492 Evaluation of Major Salt Deposits of Pakistan. Journal of the Chemical Society of Pakistan,
493 29: 569.
494 Sharp, Z., and Draper, D. 2013. The chlorine abundance of Earth: implications for a habitable
495 planet. Earth and Planetary Science Letters, 369: 71-77.
496 Sharp, Z., Barnes, J., Brearley, A., Chaussidon, M., Fischer, T., and Kamenetsky, V. 2007.
497 Chlorine isotope homogeneity of the mantle, crust and carbonaceous chondrites. Nature,
498 446: 1062.
https://mc06.manuscriptcentral.com/cjes-pubs Page 23 of 31 Canadian Journal of Earth Sciences
499 Tan, H., Ma, H., Xiao, Y., Wei, H., Zhang, X., and Ma, W. 2005. Characteristics of chlorine
500 isotope distribution and analysis on sylvinite deposit formation based on ancient salt rock
501 in the western Tarim Basin. Science in China Series D: Earth Sciences, 48: 1913-1920.
502 Warren, J. 1999. Evaporites: their evolution and economics. Wiley-Blackwell.
503 Warren, J.K. 2010. Evaporites through time: Tectonic, climatic and eustatic controls in marine and
504 nonmarine deposits. Earth-Science Reviews, 98: 217-268.
505 Wei, W., Kastner, M., and Spivack, A. 2008. Chlorine stable isotopes and halogen concentrations
506 in convergent margins with implications for the Cl isotopes cycle in the ocean. Earth and
507 Planetary Science Letters, 266: 90-104.
508 Wilson, T., and Long, D. 1993. Geochemistry and isotope chemistry of CaNaCl brines in Silurian
509 strata, Michigan Basin, USA. AppliedDraft Geochemistry, 8: 507-524.
510 Xiao, Y., Zhou, Y., and Liu, W. 1995. Precise Measurement of Chlorine Isotopes Based on Cs2Cl2
511 by Thermal Ionization Mass Spectrometry. Analytical Letters, 28: 1295-1304.
512 Xiao, Y., Yinming, Z., Qingzhong, W., Haizhen, W., Weiguo, L., and Eastoe, C. 2002. A
513 secondary isotopic reference material of chlorine from selected seawater. Chemical
514 Geology, 182: 655-661.
515 Yechieli, Y., Kafri, U., and Sivan, O. 2009. The inter-relationship between coastal sub-aquifers
516 and the Mediterranean Sea, deduced from radioactive isotopes analysis. Hydrogeology
517 Journal, 17: 265-274.
518 Ying-kai, X., Wei-guo, L., Yin-min, Z., Yun-hui, W., and Shirodkar, P. 2000. Variations in
519 isotopic compositions of chlorine in evaporation-controlled salt lake brines of Qaidam
520 Basin, China. Chinese Journal of Oceanology and Limnology, 18: 169-177.
https://mc06.manuscriptcentral.com/cjes-pubs Canadian Journal of Earth Sciences Page 24 of 31
1 Table1: Detailed stratigraphy of the Salt Range Formation. Thickness and the lithology of the 2 exposed rock from the Khewra Salt Mine are presented. Stratigraphy sequence(s) Subdivision/Description Thickness (m)
New division Old division
Sahwal Marl Upper gypsum dolomite Crystalline to non-crystalline 0-20
Upper saline marl a) Bright red marl + minor salt seams >80
b) Dull red marl + gypsum (3m at top) 50
Bandrakas Gypsum Middle gypsum Crystalline to non-crystalline 50
Billianwala Salt Lower or main saline marl Halite + sometimes intermixed with >650
Draftgypsum beds
Lower gypsum dolomite Base is not exposed >100
3
4
5
6
7
8
9
10
https://mc06.manuscriptcentral.com/cjes-pubs Page 25 of 31 Canadian Journal of Earth Sciences
11 Table 2: δ37Cl and ion compositions of the halite samples. SPW: South Pharwala, KS: Potash 12 Seam, MPW: Middle Pharwala, NPW: North Pharwala, TS: Thin Seam, S: Sujowal, B: Buggy, 13 NB: North Buggy.
- 2- + + 2+ 2+ 3+ - - 37 Sample Location Cl SO4 Na K Ca Mg B Br NO3 δ Cl (Wt. %) (Wt. %) (Wt. %) (Wt. %) (Wt. %) (Wt. %) (Wt. %) (Wt. %) (Wt. %) (‰) KH17-1 NLLT 51.05 6.96 36.41 0.32 0.23 0.13 0.0034 0.0080 0.0375 -0.62 KH17-2 SPW 59.43 1.36 38.71 0.22 0.21 0.06 0.0003 0.0105 0.1262 -1.04 KH17-3 SPW 59.35 1.47 38.50 0.32 0.24 0.13 0.0005 0.0089 0.1366 -0.91 KH17-4 KS 36.68 27.21 24.21 7.55 0.03 4.31 0.0052 0.0097 0.1117 -0.58 KH17-5 KS 44.85 0.31 22.30 9.41 0.01 0.06 0.0003 0.0340 0.0948 -0.74 KH17-6 MPW 60.28 0.16 39.00 0.15 0.02 0.02 0.0012 0.0092 0.1534 -0.28 KH17-7 KS 47.61 8.10 31.91 1.44 1.35 0.65 0.0106 0.0064 0.0326 -0.49 KH17-8 KS 40.33 7.71 19.14 9.73 0.03 1.38 0.0014 0.0281 0.0904 -0.73 KH17-9 NPW 54.14 3.81 35.40 0.77 0.52 0.45 0.0072 0.0093 0.0239 -0.81 KH17-10 NPW 60.45 0.12 39.18 Draft0.06 0.04 0.01 0.0000 0.0074 0.1795 -0.13 KH17-11 NPW 60.16 0.29 38.94 0.13 0.10 0.08 0.0000 0.0082 0.0658 -0.34 KH17-12 NPW 45.65 6.73 30.43 1.30 1.18 0.49 0.0082 0.0054 0.0300 -0.01 KH17-13 TS 60.30 0.20 39.05 0.10 0.04 0.02 0.0001 0.0100 0.1863 -0.46 KH17-14 TS 49.69 12.67 31.31 3.80 0.02 2.5 0.0022 0.0240 0.1391 -0.49 KH17-15 TS 57.85 3.15 38.74 0.10 0.07 0.08 0.0001 0.0111 0.0687 -0.15 KH17-16 TS 58.63 2.21 38.62 0.27 0.25 0.02 0.0001 0.0076 0.0992 -0.84 KH17-17 MPW 60.49 0.18 39.21 0.05 0.02 0.04 0.0003 0.0243 0.1752 -0.83 KH17-18 MPW 58.27 2.69 38.02 0.55 0.19 0.28 0.0005 0.0072 0.1231 -0.15 KH17-19 MPW 60.19 0.52 39.09 0.10 0.07 0.03 0.0003 0.0096 0.0993 -0.16 KH17-20 MPW 53.49 0.40 31.01 2.29 0.02 1.35 0.0005 0.0085 0.0734 -0.13 KH17-21 S 49.30 12.68 37.90 0.04 0.02 0.06 0.0009 0.0183 0.1451 -0.18 KH17-23 S 59.67 1.11 39.03 0.08 0.05 0.05 0.0000 0.0095 0.1314 -0.20 KH17-22 S 60.22 0.47 39.04 0.14 0.08 0.04 0.0001 0.0103 0.0848 0.73 KH17-24 B 59.69 1.13 39.03 0.04 0.01 0.11 0.0005 0.0075 0.1175 0.02 KH17-25 B 59.37 1.54 38.56 0.16 0.11 0.25 0.0004 0.0091 0.1158 0.08 KH17-26 NB 59.33 1.48 38.52 0.29 0.27 0.11 0.0020 0.0078 0.0972 0.67 KH17-27 NB 56.31 4.83 36.54 0.20 0.13 0.05 0.0014 0.0076 0.0290 1.07 KH17-28 NB 54.08 7.42 38.26 0.05 0.008 0.18 0.0007 0.0229 0.1530 0.61
https://mc06.manuscriptcentral.com/cjes-pubs Canadian Journal of Earth Sciences Page 26 of 31
14 Table 3: Comparison of the chlorine stable isotope compositions of worldwide potash promising 15 basins. Sources: Qarhan Salt Lake, Mengye Yunnan, Navarra Basin, Catalonia Basin, Spain, 16 Sitaluobin and Mahai Salt Lake from Tan et al. (2005); East Siberia & Holbrook Basin from Eastoe 17 et al. (2007); Gulf of Mexico from Eastoe et al. (2001); Salt Range from this study. 18 Region Sample 37Cl/35Cl ± (2σ) δ37Cl (‰)
Qarhan Salt Lake, China Salt (0.7― 0.8m depth) 0.31912±0.00004 -0.44 Modern carnallite 0.31882±0.00006 -1.38
Mengye Yunnan, China White salt 0.31914±0.00004 -0.38 China Sage green sylvinite 0.31904±0.00006 -0.69 Caesious sylvinite 0.31898±0.00004 -0.88
Navarra Basin, Spain Pink sylvinite 0.31898±0.00016 -0.88 Red sylvinite 0.31849±0.00011 -2.41 Carmine sylvinite 0.31902±0.00003 -0.74
Catalonia Basin, Spain Salt (lower zone) 0.31958±0.00005 1.00 White salt 0.31941±0.00008 0.47 Pink salt 0.31945±0.00006 0.60 Red sylvinite 0.31913±0.00005 -0.41 CarnalliteDraft 0.31887±0.00006 -1.22
Sitaluobin, Belarus Salt (S-84) 0.31924±0.00003 -0.06 Sylvinite (S-83) 0.31880±0.00017 -1.44 Sylvinite (S-80) 0.31855±0.00004 -2.22 0.31843±0.00017 -2.60
Mahai Salt Lake, China Salt 0.31913±0.00003 -0.21 Early sylvinite deposit 0.31891±0.00003 Early carnallite deposit 0.31864±0.00002 -0.90 -1.88
East Siberia With sylvite (Angara Fm.) -0.8 With sylvite (Usolye Fm.) -0.9 With sylvite (Belsk Fm.) -0.6 With Carnallite (Angara 0.9 Fm) Above sylvite -0.4 to +0.1 (Angara Fm.)
Holbrook Basin, Arizona Potash facies (Supai Fm.) - -0.4 With sylvite (Supai Fm.) -0.9 -
Gulf of Mexico Louann & Potash - -0.5 Haynesille salt
Halite (pink) - -0.15 Halite (white) -0.13 Salt Range, Pakistan Sylvite - -0.49 to -0.73
19
https://mc06.manuscriptcentral.com/cjes-pubs Page 27 of 31 Canadian Journal of Earth Sciences
Figures
Draft
Fig. 1. Location and geological maps of the sampling area. (A) Location map of the study area. (B) Geographical map of the Salt Range. (C) Working area and distribution of the informal sub- units of the Salt Range Formation in the Khewra Mine (after Richards, 2015).
https://mc06.manuscriptcentral.com/cjes-pubs Canadian Journal of Earth Sciences Page 28 of 31
Draft
Fig.2. (A) Stratigraphic column (after Grelaud et al., 2002). (B) The Salt Range Member subdivisions (after Ghazi et al., 2015).
https://mc06.manuscriptcentral.com/cjes-pubs Page 29 of 31 Canadian Journal of Earth Sciences
Draft
Fig.3. Variations of the δ37Cl (‰) and Cl/Br ratios of halite from the Salt Range formation. The seawater evaporation pathway is also reported: the black line is taken from Eggenkamp et al., 1995 and the blue one from Eastoe et al., 1999). Note that the seawater evaporation process proceeds from right to left.
https://mc06.manuscriptcentral.com/cjes-pubs Canadian Journal of Earth Sciences Page 30 of 31
Draft
Fig. 4. Na-Cl-Br systematics in the Salt Range halite. Square symbol: seawater. Blue line: seawater evaporated past halite precipitation and solid (black) line: theoretical chemical compositions resulting from the dissolution/recrystallization of halite.
https://mc06.manuscriptcentral.com/cjes-pubs Page 31 of 31 Canadian Journal of Earth Sciences
Draft
Fig. 5. Range of 37Cl for the Salt Range Formation compared to those of promising potash basins worldwide (data taken from the literature and available in Table 3).
https://mc06.manuscriptcentral.com/cjes-pubs