Among the above rocks and minerals, Artemia fossils and Artemia larvae fossils occupy a very important position.
I. Dolomite and salt-dissolved breccia
Dolomite is light gray, yellow gray and dark gray, which can be divided into argillaceous, calcareous, microcrystalline dolomite, gypsum micrite dolomite, semi-automorphic dolomite and automorphic dolomite. Plate 9- 1 is coarse-grained dolomite with unequal grain semi-self-shaped double worm structure. The morphology of dolomite particles depends entirely on the aggregation and bonding of two kinds of insect fossils. The edges of dolomite particles are often surrounded by Artemia solid fossils. The middle is mostly composed of Artemia larva molting fossils and Artemia larva molting fossils.
Salt-dissolved breccia (Wei Dongyan, 199 1) is one of the most common rock types in salt-bearing systems. Illustration 9-2 shows the outcrop of salt-dissolved breccia in the Ordovician salt-bearing system in Xing County, Shanxi Province. The arrow 1 in the figure refers to the black Artemia solid fossils, and the yellow breccia is common with Artemia solid fossils, and brown ones can also be seen, among which there are many Artemia fossils with head, chest and abdomen, which are swimming; Arrow 2 refers to the circular fecal fossils of Artemia larvae; Arrow 3 refers to the fossils of Artemia larvae.
Secondly, dolomite containing halite and gypsum pseudocrystals.
Pseudocrystalline microcrystalline dolomite containing halite (Plate 9-3) has a porphyritic microcrystalline structure. Both phenocrysts and substrates have double worm structures. The black ones in the matrix are mostly Artemia solid fossils, and the white ones are Artemia larvae molting fossils. The speckled pseudocrystals of halite are square, oval or irregular, and consist of Artemia larva fossils and Artemia fossils (mainly molting fossils). Some fossils break through the edge of phenocryst, which makes the edge of phenocryst appear burr-like.
Pseudocrystalline limestone dolomite containing gypsum (Plate 9-4) has a porphyritic microcrystalline structure. Both phenocrysts and substrates have two insect structures. Spotted gypsum pseudocrystals are rectangular, and consist of many molting fossils of Artemia larvae (white), small molting fossils of Artemia larvae (gray) and a few large molting fossils of Artemia larvae (white).
Three, dolomite and suture
Dolomite with suture has a semi-self-shaped near-equigranular mosaic structure (Figure 9-5). Rhombic and quadrilateral dolomites are formed by polymerization of Artemia and molting fossils of Artemia larvae.
Regarding the suture, geologists believe that the suture is formed by uneven dissolution of rocks (epigenetic period) under pressure, and the residual iron and organic matter in the dissolution process are dark gray and black. Careful observation shows that the so-called dissolved residue in the suture may actually be caused by the accumulation of gray-black Artemia solid fossils (very few are Artemia larvae fossils) into strips. Therefore, the theory of suture pressure dissolution is debatable.
Four. Bamboo dolomite
Bamboo-leaf dolomite has a semi-automorphic granular mosaic structure with two insects (Figure 9-6). Most dolomite particles consist of multiple molting fossils of Artemia larvae, and a few are single molting fossils of Artemia larvae. Artemia fossils (gray-black) either exist alone in the gaps of dolomite particles or aggregate into strips. The long axes of Artemia fossils are arranged in parallel in arc strips, which look like bamboo leaves to the naked eye.
Verb (abbreviation for verb) anhydrite rock
Anhydrite in the salt basin is layered alone, coexisting with rock salt and potassium salt, or dispersed in dolomite. Anhydrite is often nodular, massive, tumor-like, intestinal, chicken cage wire-like, etc. Studies have shown that anhydrite consists of two kinds of insect fossils, no matter what form or polymer it takes. Panel 5-23 shows intestinal anhydrite. It can be seen that the molting fossils of Artemia larvae and Artemia larvae are horizontally or nearly vertically closely inlaid and aggregated into intestines. Sometimes Artemia fossils (gray-black) can be seen vertically distributed along the long axis of the core.
Six, rock salt
Rock salt is the main rock type of salt-bearing system. The rocks are grayish white, light gray, soot-colored, light brown and brown, and some are colorless and transparent. The main mineral is halite, in addition to a small amount of impurities: argillaceous, dolomite, magnesite, anhydrite, potassium salt, authigenic time, pyrite and hematite. The research shows that the minerals in halite, whether it is the main mineral halite or the minor and trace minerals, are all composed of Artemia and Artemia larva fossils. Detailed research shows that there are more Artemia fossils in rock salt than Artemia larvae fossils. Plate 9-7 is halite containing pyrite, and the cubic particles of halite are composed of molting fossils of Artemia larvae, surrounded by solid fossils of Artemia. Generally speaking, two groups of nearly vertical cleavage are actually composed of two nearly vertical Artemia solid fossils. In the black anhydrite pyrite belt, square or nearly square pyrite is also composed of Artemia fossils, which may contain bacteria and algae. The white one in the middle of the right side of the picture is the fossil of Artemia larvae, and you can see the obvious hind feet.
Magnesite is usually contained in rock salt (Figure 9-8). Magnesite is a nonstandard rhombus with the sizes of 0.56mm× 1mm and 0.56mm× 1.2mm, which is composed of Artemia larvae molting fossils, Artemia larvae molting fossils (light color) and dark gray Artemia fossils, and the crystals are surrounded by linear dark Artemia fossils. The obvious sign of determining Artemia fossils is that there are two inverted eight-shaped tentacles at the top of the head, and the chest is wide and the abdomen is narrow.
Red-brown halite usually contains fine flake hematite in the form of rhombus, meniscus and rod (Illustrations 9-9). It is more common for potassium salt and hematite to coexist closely. Flake hematite consists of tiny parts of Artemia appendages of smaller Artemia larva molting fossils, while the edge of diamond is surrounded by tiny parts of dark Artemia larva fossils or Artemia appendages.
Seasoning is also common in rock salt. In plate 9- 10, it is a self-shaped hexagonal bipyramid, which is composed of white Artemia molting fossils, bacteria and algae. The outer six sides are surrounded by gray Artemia larvae or tiny parts of Artemia appendages.
Among halite, sylvite is usually square, rectangular and earthworm-shaped (plate 9- 1 1, plate 9- 12). In Figure 9- 1 1, the rectangular potassium salt consists of Artemia larvae molting fossils (white) and Artemia solid fossils (gray-black), and is surrounded by black solid Artemia fossils or tiny parts of Artemia appendages. In a rectangular crystal, there are five straight lines whose long sides are parallel to each other. Look carefully, each line consists of 1 Artemia solid fossil or two Artemia solid fossils. This parallel line segment composed of Artemia fossils is what we usually call a group of cleavage of potassium salts. Of course, a single Artemia fossil is inclined or perpendicular to the fossils parallel to each other in a rectangular crystal. On the right side of plate 9- 12, potassium salt is shown as earthworm. Careful observation shows that it consists of three molting fossils of Artemia larvae. Among them, the molting fossils of each Artemia larva are surrounded by Artemia solid fossils on both sides. 9- 12 disk has a long row of potassium salts obliquely distributed on the left side, which consists of white Artemia larvae molting fossils and black Artemia solid fossils.
Seven, sylvite containing halite.
Potash-bearing halite and potash halite were found in Well Yu 9, Well Shan 1 and Well Zhenchuan 1 in Ordos Basin. The potassium-bearing horizon is mainly the sixth member of the fifth member of Majiagou Formation, and there is also a small amount of dispersed potassium salt in the fourth member of the fifth member of Tang 1 Jing. Potash rock only occurs in the middle and upper part of the sixth sub-member of the fifth member of Ma in Well Yu 9, with a thickness of only 4 cm. In potash rock containing potash salt, besides potash salt, potash mineral also contains a small amount of carnallite and potassium iron salt.
Careful study under microscope shows that there are five occurrences of potassium salt in this area: first, it is distributed in rock salt, usually in the form of inclusions, generally autotype or semi-autotype; Secondly, a ring-edge structure is formed around the grain of potassium salt, and the potassium salt is semi-isomorphic. Thirdly, potassium salt and halite form granular heterostructure, and potassium salt is mostly irregular crystal; Fourthly, special granular potassium salts, such as lenticular potassium salts, show uneven mosaic structure under high magnification; Fifthly, potassium salt is a component of some Artemia feces.
No matter what the occurrence of potassium salt is, it is formed by copolymerization of a single Artemia fossil or a single Artemia larva fossil or Artemia fossil and Artemia larva fossil.
Fig. 9-13 shows the structure of two kinds of insects with round edges of halite containing potassium salt. This is a unique microscopic thin-slice structure containing potassium and potassium salts in this area. Ring-edge double helix structure refers to the ring edge formed by fine particles of potassium salt around large crystal grains of halite.
In addition to the fine particles of potassium salt, there are fine particles of red hematite and anhydrite at the edge of the ring, which together with potassium salt form a mosaic structure. The fine minerals in the ring-shaped decorative structure mentioned here-potassium salt, hematite and anhydrite-all appear in the form of Artemia larva molting fossils, Artemia larva molting fossils and Artemia solid fossils. Among them, hematite is mostly Artemia solid fossils. Sometimes, several Artemia fossils are piled together, and it is difficult to identify the shape of a single Artemia. At this time, it can be identified by a slender tail and an inverted "eight-shaped" antenna. Of course, the incomplete fossil fragments of Artemia appendages are also part of salt minerals.
Carnitine coexisting with potassium salt in this area occurs in brownish-red potassium salt-bearing rocks in the fifth sub-member of the fifth member of Ma 'an Formation in Well Yu 9. Carnitine, colorless, sometimes light rose, low negative protrusion, secondary red-green interference color, biaxial crystal positive light. Illustration 9- 14 shows polygon carnallite in rock salt. Carnitine is wrapped in inner leaf fossils separated from Artemia appendages. ), indicating that Artemia plays an important role in the formation of carnallite.
Potassium iron salt and carnallite occur in the same horizon. The potassium and iron salts in the flake are colorless, the surface is rough and obvious, the positive protrusion is low, uniaxial positive light, first-class gray interference color, and sometimes slightly blue-gray abnormal interference color. Potassium iron salt looks like a saw blade (plate 9- 15), and potassium iron salt and cristobalite are inclusions of halite. On the serrated side of potassium and iron salts, three sensory hairs at the antenna end of Artemia nauplii can be seen, which can be compared with the three sensory hairs at the antenna end of modern Artemia nauplii (plate 9- 16). Filamentous fossils on Artemia appendages can also be seen in the photos.
The study on the tiny fossils of Artemia in carnallite and potassium iron salt shows that Artemia is closely related to the formation of these two potassium salts.
Eight, clay minerals in salt-bearing system
Clay minerals are one of the important components of salt-bearing system. The comprehensive study shows that the clay minerals in this area are mainly illite and chlorite, and kaolinite is low in content and limited in distribution, mainly distributed in the desalting layer of salt-bearing system.
Plate 9- 17 shows the flaky polymer of illite in SEM photos. There are usually round or various forms of black cavities in the polymer, which indicates that there are tubular or tubular molting fossils of Artemia and Artemia larvae in the polymer, and illite appears in the form of such molting fossils.
Plate 9- 18 is a scanning electron microscope photograph of chlorite, which is self-columnar, mainly composed of molting fossils of Artemia larvae or pupae and a small amount of molting fossils of Artemia larvae.
The study shows that clay minerals and their combinations mainly depend on the composition, salinity and pH value of brine. For example, chlorite, illite and their combinations occur in the sixth submember of the fifth member of Majiagou Formation, especially in the halite-sylvite stratum rich in sylvite. Previous studies have considered that clay minerals in salt-bearing systems are formed by terrigenous detritus and silicate alteration. According to the characteristics of amphibian fossils, the author thinks that the clay minerals in the salt-bearing system are primary minerals, and their genesis is closely related to the biological-water-salt system in the basin. Clay minerals are important products in evaporite environment.