1 Paleotectonic and paleogeographic conditions for the formation and evolution of coal bearing bas

In the whole geological age of coal, there are three major coal-forming periods in the world:

In the Carboniferous and Permian periods of the Paleozoic, coal-forming plants were mainly spore plants. The main types of coal are bituminous coal and anthracite.

In the Jurassic and Cretaceous periods of the Mesozoic Era, coal-forming plants were mainly gymnosperms. The main types of coal are lignite and bituminous coal.

In the Tertiary period of the Cenozoic Era, the main angiosperms were destroyed by coal-forming plants. The main coal type is dust tolerant to lignite, followed by peat, and some young bituminous coal.

Iron ore is formed in a variety of ways, there are sedimentary rock deposits, metamorphic rock minerals, etc., and even meteorite, the time of iron ore formation has been reflected in many geohistorical periods, and the period of the formation of major iron ore in Precambrian is detailed.

During the Archean-Paleoproterozoic, the Earth's crust was very thin, and mafic-ultramafic magma from the Earth's mantle erupted over a large area in the vast oceans. At this time, during the global atmospheric hypoxia period, a large amount of iron-rich in the mafic volcanic rocks on the seafloor was dissolved in the form of ferric in the seawater, forming iron-rich seawater.

Meso-Neoproterozoic, under the influence of global cracking events, rifts, rift troughs or depression troughs of different scales were generated near the paleocontinental margin, and huge thick clastic rocks and carbonate rocks were deposited, accompanied by volcanic eruptions of different scales, forming a variety of iron ore types, such as the Dahongshan-type marine volcanic iron-copper ore in Yunnan, the Xuanlong-type marine sedimentary hematite in the Xuanhua area of the northern margin of the North China Craton, the Damiao-type magmatic iron ore in Hebei Province around the upper ga of the North China Craton, and the Lugu-type contact metasomatic hydrothermal iron ore in Sichuan.

The total iron ore formation is shown at:

It can only be said that the favorable conditions for the formation of iron ore before the Cambrian period were that the animals and plants (single cells) that produced oxygen did not exist at that time, so there was almost no oxygen on the earth, so iron could be preserved, and the common magma carried iron elements ejected out of the surface and was not weathered by oxygen.

As for the Carboniferous period, it is simple, mainly because the swamps are distributed, that is, the sea level has fallen, the rivers have developed, and swamps have been formed in many places, which are rich in ferns, so coal was formed after being buried, which is why it is called the Carboniferous.

Geologists and paleontologists divide the strata into 5 generations and 12 epochs according to the order in which the strata are naturally formed. That is, the early Archean and Proterozoic (the Proterozoic contains 1 Sinian in China), and the later Paleozoic, Mesozoic, and Cenozoic. The Paleozoic era is divided into Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian, a total of 6 epochs; The Mesozoic Era is divided into the Triassic, Jurassic and Cretaceous, with a total of 3 epochs; There are only two periods in the Cenozoic: the Tertiary and the Quaternary.

Answer]: The emergence and evolution of human fronts is one of the most important events in the Quaternary, and glaciation is another major event in the Quaternary. Volcanic activity and tectonic movement also existed in the geological period before the Quaternary.

It is Carboniferous, Permian, Jurassic.

The Carboniferous coal accumulation period was mainly in the Late Carboniferous, forming the coal measures in North China, East China and Central and South China, the famous Taiyuan Formation coal measures were formed in this period, and the large mining areas in Shanxi and Hebei such as Xishan, Kailuan, Yangquan, Jincheng, Lu'an, Fenxi, etc. all belong to the coal measures;

Both the Early Permian and the Late Permian had strong coal accumulation, and the Early Permian mainly formed the Shanxi Formation coal measure centered on North China. In the Late Permian, the Longtan coal measure in Guizhou was mainly formed.

During the Jurassic period, due to the "Yanshan Movement" throughout the country, the largest number of coalfields were formed during this period, mainly concentrated in North China and Northwest China. The famous coalfields mainly include Shenfu, Dongsheng coalfield, Datong coalfield and undeveloped coalfield in Xinjiang; The Jurassic coalfield has the most abundant reserves.

In the whole geological epoch, there are three major coal-forming periods in the world: (1) In the Carboniferous and Permian of the Paleozoic, coal-forming plants were mainly spore plants. The main types of coal are bituminous coal and anthracite.

2) In the Jurassic and Cretaceous of the Mesozoic Era, coal-forming plants were mainly gymnosperms. The main types of coal are lignite and bituminous coal. (3) In the Tertiary of the Cenozoic, coal-forming plants were mainly angiosperms.

The main type of coal is lignite, followed by peat, and some young bituminous coal.

When you read some books or movies on the theme of dinosaurs or paleontology, you will always hear some unbelievable geological chronological names, such as Devonian, Silurian, Ordovician, Cretaceous and so on. So how exactly is the geological age of the earth divided? How did these names come about?

Carboniferous--- Permian, Triassic--- Jurassic, Tertiary.

1.Evolutionary stages of rift action.

According to the nature of the earth's crust and the degree of lithospheric cracking, rift basins have gone through several evolutionary stages from the initial intracontinental rift to the formation of the final passive continental margin basin. Salveson (1978) divides it into five periods (Figs. 9-7): pre-rift graben formation rift basin rift basin mature continental margin.

Liu Hefu (1993) summarized it into three stages: the continental rift stage, which is often related to the thermal uplift of the mantle, and forms a barrier-trench structure, without oceanic crust intrusion; In the intercontinental sea stage, continental drift began, and the oceanic crust began to invade and accretify along the mid-ocean ridge, and the Red Sea basin was the product of rifting in this stage. In the continental margin stage and the continental drift period, large-scale subsidence and expansion occurred, and the sedimentation rate exceeded the subsidence rate, and a thick accumulation wedge was formed. In fact, the first stage classified by Liu Hefu (1993) corresponds to the pre-rift and graben formation period of Salveson (1978), the second stage corresponds to the rift basin and rift basin of the latter, and the third stage corresponds to the mature continental margin of the latter.

2.Types of rift action.

According to the genetic characteristics of rifting, it can be divided into active rift (or mantle cause rift) and passive rift (or lithospheric cause).

Active rifting is when a thermal mantle column hits the lithosphere, causing the lithosphere to thin, dome, and arch up, thereby extending the earth's crust. The East African Rift Valley is one of these types. In the early stage of the formation of this rift, regional vaults, arches and uplifts were produced.

Volcanism is produced by high heat flow activity.

Figure 9-7 Evolution stage of rift action.

According to Salveson, 1978).

Passive rifting refers to the thinning of the earth's crust and the passive upwelling of the asthenosphere caused by the tensile stress of the lithosphere. Such as the Rio Grande Rift.

The main difference between the two types of rift is that the heat source and stress have opposite causal relationships, and they have different tectonic evolution, tectonic styles, magmatic activity and sedimentary filling patterns. The former is deposited on the unconformity caused by the initial uplift and lacks detritum. The early deposits of the latter had an inflow of water systems and were not lacking in detritus.

3.Evolutionary pathways of rift basins.

There are many factors that affect the type of rift basin formed by extensional lithosphere, or how continental rift basins or rift basins evolve after formation. Lu et al. (2006) summarized five evolutionary pathways of rift basins based on the tectonic development process of rift basins in different regions and different eras in the world.

1) Continental Rift-Intercontinental Rift-New Ocean Basin;

2) Continental Rift-Recession Rift-Ola Valley;

3) Continental Rift - Passive Continental Margin;

4) Continental rift valley or rift basin - intracontinental depression basin;

5) Continental rift basin-extensional tectonic belt.