Chronological and rock magnetic constraints on the transition of the Quaternary paleoclimate in the western Qaidam Basin, NE Tibetan Plateau

A closed Quaternary saline paleolake, currently still a lake and named Dalangtan after one of its largest sub-basins, has widely distributed sediments in the western Qaidam Basin, NE Tibetan Plateau. Lacustrine salt minerals and fine sediments from this paleolake provide an environmental record for investigating paleoclimatic evolution in the Asian interior. However, detailed continuous Pliocene–Quaternary paleoclimatic records are broadly lacking from the NE Tibetan Plateau owing to poor exposure of the outcrops in section. For this study, we performed a detailed magnetostratigraphic dating and rock magnetic analysis on a 590-m-long core from the SG-5 borehole in the western Qaidam Basin. The results demonstrate that the lacustrine sediments in the SG-5 borehole were deposited more than ~3.0 Ma. Saline minerals began to increase at 1.2 Ma, and the magnetic susceptibility (χ) also changed at that time; the percentage frequency-dependent magnetic susceptibility was relatively low and uniform throughout the whole core. These observations, combined with the χ, pollen, salt ion, and grain-size records from other boreholes, indicate that the western Qaidam Basin and the greater Asian interior had a significant climate transition at 1.2 Ma during an extreme drought.

Micron-Nanometer Evaporite Mineral Compositions in the Jiangling Depression, Jianghan Basin, China, by Means of Scanning Electron Microscopy

Scanning electron microscopy (SEM) was used to analyze and study micron-nanometer evaporite samples collected from Paleocene and Eocene drill cores in the Jiangling Depression. Accordingly, seven beds of potassium-bearing solid rocks were accurately identified. Sylvite, carnallite, syngenite, dolomite, thenardite, anhydrite, glauberite, halite, barite, celestite, and other solid salt minerals were found, and carnallite, syngenite, and thenardite were found for the first time in the Jiangling Depression. Sylvite, syngenite, and carnallite indicate that the Paleogene salt lakes in the Jiangling Depression had evolved to the sylvite stage and that prospecting for solid sylvite would be satisfactory. Micron-nanometer celestite is contained in the evaporites, from which we can infer that strontium may have been provided by deep formation water (or oil-field water). This finding is of great significance to studying the genesis of sylvite sediment in the Jiangling Depression. From the extensive development of primary glauberite beds typical of warm salt minerals in the Shashi Formation, it can be inferred that the late Paleogene paleoclimate in the Jiangling Depression of the Jianghan Basin was dry and hot. Based on the extensive distribution of micron-nanometer pyrite, siderite, iron and Fe2O3/FeO ratios in evaporite sediments and color analysis of mudstones, the evaporites in the study area formed in an underwater anoxic, reducing environment during sedimentation. Therefore, the evaporite sediments in the Paleocene–Eocene interval of the Jiangling Depression are proposed to have formed in a saltwater lake sedimentary environment, and the ancient lake was characterized by a deep-water salt lake sedimentary model.

Effects of Dissociation Water Retention on Pore Structure Disintegration in Hydrate Sediments

During the depressurization process, natural gas hydrates (NGHs) decompose and release methane gas and water. Field experience shows that only 1% of the dissociation water is recovered, hindering the continuous pressure decline and further NGHs decomposition. The retention effect of the dissociation water on the pore structure is still unclear in NGHs sediments. In this paper, the hydrate sediment samples were tested for porosity, permeability, pore structure and clay minerals content, etc. The ions concentration change of solution was continuously measured using a conductivity meter to evaluate the disintegration mechanism of sediments. The results show that the pore structure of sediments tend to disintegrate under the action of dissociation water, leading to an increase in the ions concentration of dissociation water. According to the ions concentration curve, the sediment disintegration is divided into two stages. The rapid disintegration stage is mainly related to clay minerals. The slow disintegration stage is mainly related to the dissolution of soluble salt minerals. The initial water content is the main factor affecting the disintegration of the sediment skeleton. Under the condition of low initial water content, the sediment skeleton disintegrates instantaneously in dissociation water. When the initial water content exceeds 30.6–37.9%, the pore structure of sediments tends to be stable in dissociation water. Studying the effect of dissociation water on the sediment pore structure is helpful to understand the mechanism of low water production and to optimize the exploitation regime of gas hydrate.

Potensi Kualitatif Produksi Garam dari Perairan Pantai Lubuk dan Pantai Takari, Bangka Belitung

Garam-garaman tersedia di air laut sebagai sumberdaya alam yang melimpah, garam ini diekstraksi untuk memenuhi kebutuhan manusia sehari-hari. Penelitian bertujuan untuk mengetahui potensi kualitatif produksi garam dari Pantai Lubuk dan Pantai Takari, Bangka Belitung. Dua metode sebagai perbandingan yaitu metode perebusan di Pantai Lubuk Desa Lubuk, dan metode penjemuran konvensional air laut yang dilanjutkan rekristalisasi di Pantai Takari Desa Rebo. Analisis potensi kualitatif garam krosok ini membandingkan dengan lokasi lain dan standar SNI. Hasil penelitian menunjukan bahwa potensi kualitastif produksi garam dari Pantai Lubuk dan Pantai Takari cukup menjanjikan karena mampu bersaing dengan produksi dari wilayah lain dan kualitasnya masih dapat ditingkatkan. Berdasarkan metode perebusan tradisional diperoleh kadar NaCl bernilai 89,98%, sementara dengan cara dijemur konvensional dan direkristalisasi bernilai 90,94%, nilai ini menunjukan bahwa kadar NaCl masih di bawah standar SNI yang bernilai 94,0%. Namun demikian, hasil garam ini masih dapat dipergunakan untuk pengasinan ikan, campuran pakan, dan pupuk. Kualitas garam dari Pantai Lubuk dan Pantai Takari untuk Kadar KIO3 tidak terdeteksi, Kadar Bagian yang Tidak Larut dalam Air bernilai 8,98% dan (-); Kadar Air bernilai 2,23% dan 13,10%; Unsur zat pencemar Cd, Pb, Hg, As (dari Pantai Lubuk tidak terdeteksi dan dari Pantai Takari <0,0108, <0,0077, <0,0002, <0,0001). Dengan demikian, penelitian lanjutan diperlukan untuk meningkatkan kualitas garam menjadi lebih baik menuju kualitas standar. Kualitas garam yang baik secara ekonomi dapat menguntungkan sebagai alternatif mata pencaharian masyarakat pesisir di Desa Rebo dan Desa Lubuk. Various salt minerals are available in sea water as an abundant natural resource. This salt can be extracted to meet everyday human needs. This study aims to determine the qualitative potential of salt production from Lubuk Beach and Takari Beach, Bangka Belitung. Two methods were compared: the boiling method (at Lubuk Beach, Lubuk Village) and the conventional seawater drying method followed by recrystallization (at Takari Beach, Rebo Village). the quality of krosok salt analysis was compared with the salt quality from other locations and SNI standards. The results showed that the qualitative potential of salt production from Lubuk Beach and Takari Beach is quite promising because it can compete with production from other regions and its quality can still be improved. Based on the traditional boiling method, the NaCl content in salt was 89.98%, while conventional and recrystallized drying method was 90.94%, this value indicates that the NaCl content was still below the SNI standard (94.0%). However, this salt can still be used for fish salting, feed mixtures and fertilizers. The salt from Lubuk Beach and Takari Beach did not show KIO3 levels, the water-insoluble portion content was 8.98% and (-); Water content was 2.23% and 13.10%; Pollutant elements Cd, Pb, Hg, As (undetectable from Lubuk Beach and from Takari Beach <0.0108, <0.0077, <0.0002, <0.0001). Further research is needed to improve the quality of salt to be better towards standard quality. Economically good quality salt can be beneficial as an alternative livelihood for coastal communities in Rebo and Lubuk villages.

Pore structure and controlling factors of dolomite-bearing high-salinity shale reservoir in Qianjiang Formation, Jianghan Basin, China

High-salinity shale is a unique and promising shale-oil reservoir in continental basins. We have collected representative samples from different lithologies from wells in the Qianjiang Depression to test the pore structure and basic character from prospective high-salinity oil-bearing shales. We conducted field emission scanning electron microscopy and X-ray diffraction analyses to study the high-salinity shale pore morphology and composition, respectively. We used mercury injection capillary pressure to understand the high-salinity shale macropore distribution, and we used low-pressure nitrogen (N2) adsorption to study the mesopore distribution. The results show that the high-salinity shale-oil reservoir mainly is composed of carbonate (dolomite and calcite), clay, and saline minerals (anhydrite, glauberite, and halite). Many intergranular pores were developed in the high-salinity shale. The mesopores and macropores both were developed well in argillaceous dolomite. The average pore volume of macropores is 0.0588 ml/g, which accounts for approximately 59% of the total pore volume. Therefore, in the high-salinity shale-oil reservoirs that we tested, macropores were more important than other pores. The symbiosis of dolomite and calcite improved the porosity of the high-salinity shale-oil reservoir, and the salt minerals increased the pore complexity.

The hidden CO2 – The occurrence, distribution and composition of fluids in various salt minerals

&lt;p&gt;Fluid inclusions are voids enclosed in the rock matrix and contain, depending on their origin and development, various amounts of gaseous, liquid or solid phases. Depending on their occurrence within the crystalline structure or in healed micro-fractures, primary and secondary inclusions can be distinguished. Their characteristics are utilized in various geological settings to reconstruct rock history and fluid involvement. Fluid inclusions could also be considered to be small equivalents to large cavities. As salt is regarded a favorable host rock for the storage of natural gas and other materials in artificial caverns, knowledge on gas migration and retention is crucial.&lt;/p&gt;&lt;p&gt;Here, we present results of a fluid inclusion study in various salt rocks using Raman spectroscopy in addition to conventional microscopic characterization and gas analysis on whole rock samples. This approach allows for a better understanding of fluid generation and migration in different salt lithologies over geological times.&lt;/p&gt;&lt;p&gt;Various salt minerals (halite, sylvite, kieserite and carnallite) from an area of potential overprint of CO&lt;sub&gt;2&lt;/sub&gt;-dominated gas migration were investigated. Numerous fluid inclusions exhibit chevron structure and are small sized. Large single- or two-phased inclusions are observed with irregular shapes, often indicative for leakage or necking down. Interestingly, although the CO&lt;sub&gt;2&lt;/sub&gt; concentrations in whole rock samples were high, fluid inclusions were dominated by an aqueous phase and often contain numerous daughter minerals. This suggests that CO&lt;sub&gt;2&lt;/sub&gt;-rich gas is stored along distinct fractures or grain boundaries within an otherwise intact rock.&lt;/p&gt;

Mineralogy and petrography of the Keban Pb-Zn-(Cu) skarn deposit, Elaziğ, eastern Turkey

&lt;p&gt;The Keban Pb-Zn-(Cu) skarn deposit in the Elaz&amp;#305;&amp;#287; region, Turkey, was formed at the contact zone of the Permo-Triassic metamorphics and the Late Cretaceous plutonic rocks in the Eastern Taurus orogenic belt. The mineralization is hosted by skarn and meta-clastic/carbonate rocks of the Keban Metamorphics intruded by alkali syenite porphyry, which is associated with the Pb-Zn-(Cu) mineralization. The rock units in the region are partly hydrothermally altered graphite calc-schist containing crystallized limestone interlayers and lenses, meta-pellitic rocks (phylitte/calc-phyllite), dolomitic limestone, calc-silicate hornfels, marble and plutonic rocks. Calc-silicate hornfels is an initial metamorphic product occurred in contact zone of the intrusive unit. Results of mineralogical studies indicate that garnet and pyroxene-rich skarn formed in early (prograde) stage of skarnization whereas epidote, chlorite, tremolite, phlogopite, muscovite, calcite, quartz and fluorite are typical minerals of the retrograde stage. Using the Raman spectroscopy investigations, garnets in alteration zone are subdivided into two groups. Garnets in andradite composition are zoned and occur close to the intrusion reflecting high-temperature conditions and those of grossular composition represent low-temperature conditions. The sill/dykes and stock-like Keban plutonic rocks hosting foid syenite porphyry and nepheline syenite are of holocrystalline hipidiomorph porphyritic texture including large nepheline and plagioclase phenocrysts. Metallic minerals comprise sphalerite, galena, chalcopyrite, magnetite, bornite, pyrite, fahlore and hematite, which mainly occur as dissemination, vein and massive forms and crosscut by late-stage quartz, fluorite and calcite veinlets. Sphalerite is medium-coarse grained, semi-euhedral and contain chalcopyrite inclusions. Blebs of chalcopyrite are widely recognized in sphalerite (chalcopyrite disease). Galena replaces sphalerite and in some cases, it hosts several sulfo-salt minerals. Magnetite partly or completely transforms to limonite and chalcopyrite inclusions in sphalerite occur among the magnetite grains.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Key words: &lt;/strong&gt;Keban, Pb-Zn-(Cu) skarn deposits, Mineralogy, Petrography, Ore Microscopy, Raman Spectroscopy&lt;/p&gt;

Salt, sediments and weathering environments in Bunger Hills

Terrestrial environments at Bunger Hills, East Antarctica, vary from vegetation-rich, little-weathered rock surfaces retaining glacial polish and striations near the glacier and ice-sheet margins to salty, vegetation-poor, extensively weathered regions near to and downwind of marine bays and inlets. Weathering forms include tafoni and orientated pits, which record former wind directions. Although salts are found all over Bunger Hills, the strongly weathered area is coincident with the distribution of halite (NaCl) and thenardite (Na2SO4), both of which are derived from seawater and marine salt spray. Salts elsewhere in Bunger Hills are either subglacial calcium carbonates or rock weathering products including gypsum (CaSO4⋅2H2O) and a range of rarer minerals. These other salt minerals do not weather rocks and sediment. The distribution of halite and thenardite acts as a major control on the geomorphology, sediment geochemistry and biogeography of Bunger Hills.