CATATAN GEOLOGI GEOLOGICAL NOTES ISSN 0126–5539; e-ISSN 2682-7549 Warta Geologi, Vol. 45, No. 2, April-June 2019, pp. 31–39 The enigma of the Bario salt produced in the highlands of northern Sarawak Franz L. Kessler 1,* , John Jong 2 , Mazlan Madon 3 1 Goldbach Geoconsultants O&G and Lithium Exploration, Germany 2 JX Nippon and Gas Exploration (Malaysia) Limited, Malaysia 3 Advisor, Malaysian Continental Shelf Project, National Security Council, Malaysia * Corresponding author email address: franzlkessler32@gmail.com Abstract: The Bario/Kelabit Highlands, located in northern Sarawak is famous for its rice. One of Bario’s hidden treasures, however, is its salt, produced from the many salt springs in the area but sold in small quantities at the local marketplace such that its existence is not well known outside of Sarawak. The Bario salt is probably of non-marine origin but its actual origin is not clear. A new salt analysis, in the context with older salt spring data, has enabled a comparison with other non-marine salts. In particular, the presence of borate and lithium points to potential affinities with non-marine highland salts, such as those found in Argentina, Bolivia, Nevada and Tibet, as well as with phreatic brine salt such as the Jadar deposit in Serbia. The marked content of iodine makes allusion to brines in the vicinity of hydrocarbon-bearing reservoirs. Given that the Bario salt contains hardly any sulphate, and very little calcium, the source of the salt is unlikely to be an evaporite-bearing rock in the subsurface as previously thought. Nonetheless, there should be more fieldwork conducted and analyses made on the highland salt deposits and associated brines in northern Sarawak to provide a better understanding of their geochemical composition and origin. Keywords: Malaysia, Sarawak, Bario, Kelabit, saltwater spring, salt composition INTRODUCTION The exploration for lithium, a highly sought-after metal in the context of electricity storage, has prompted renewed research about saline brines. A comparison of world-wide lithium brines is given by Garrett (2004). Boschetti et al. (2007) describes the habitat of saline brines including the importance of isotopes. Presentations by Orocobre (2016), and SaltWorks (2017), focus on the facies of saline lakes, and their lithium potential, as well as lithium brine production characteristics. The Bario salt, produced in the remote highlands of northern Sarawak served an isolated human population, cattle and wild animals alike since unrecorded times. “Salt hunters” (a term used during the reign of the white Rajahs) extracted the salt from the salt spring, by boiling the brine water in a big pot until the salt forms a greyish layer, then collect the salt from the bottom. This process is still followed until today. The salt is dried completely and inserted into bamboo pipes, which are heated over a fire for 24 hours to harden the salt. The final step is wrapping the salt into big leaves for storage in order to keep it dry and safe for the long journey home. The wrapped salt is sold in bamboo cylinders. Naturally brownish grey, Bario salt’s colour is intentionally preserved. It is less salty than commercially available alternatives, partly due to the low magnesium content. Nevertheless it is highly sought-after due to its high, natural mineral contents. A commercially available sample is shown in Figure 1. Surprisingly, little is known about the origin of the salt and its geochemical composition. Obviously, the presence of salt in a tropical monsoon climate remains an enigma. As shown in Figure 2, salt deposits do not normally occur in monsoon-wet equatorial regions. In this paper we have attempted to assemble as much openly available information (Geological Survey reports and the internet) and performed a salt brine analysis. The new data allowed us to place Bario in context with other salt deposits throughout the world (Figure 3), and to postulate potential scenarios of how the salt may have originated. Comparing the composition of salt brines is tricky; concentrations in the literature are shown in mol, wt % or ppm, as cations or dry salt. Measured salt concentrations in salt lakes are not constant, but fluctuate due to occasional rainfall and fluid circulation Figure 1: Bario salt wrapped in bamboo leaves.