![Location of junggar basin](https://upload.wikimedia.org/wikipedia/commons/a/a5/Location_of_junggar_basin.svg)
The Junggar Basin () is one of the largest
sedimentary basin
Sedimentary basins are region-scale depressions of the Earth's crust where subsidence has occurred and a thick sequence of sediments have accumulated to form a large three-dimensional body of sedimentary rock. They form when long-term subsidence ...
s in
Northwest China
Northwest China () is a statistical region of China which includes the autonomous regions of Xinjiang and Ningxia and the provinces of Shaanxi, Gansu and Qinghai. It has an area of 3,107,900 km2.
The region is characterized by a (semi-)arid con ...
. It is located in
Xinjiang
Xinjiang, SASM/GNC: ''Xinjang''; zh, c=, p=Xīnjiāng; formerly romanized as Sinkiang (, ), officially the Xinjiang Uygur Autonomous Region (XUAR), is an autonomous region of the People's Republic of China (PRC), located in the northwest ...
,
and enclosed by the
Tarbagatai Mountains
The Tarbagatai Mountains ( mn, , , translit. ''Tarvagatai nuruu'', literally: "range with marmots"; ; kk, Тарбағатай жотасы, ''Tarbağatai jotasy'') are a range of mountains located in the north-western parts of Xinjiang, China, ...
of
Kazakhstan
Kazakhstan, officially the Republic of Kazakhstan, is a transcontinental country located mainly in Central Asia and partly in Eastern Europe. It borders Russia to the north and west, China to the east, Kyrgyzstan to the southeast, Uzbeki ...
in the northwest, the
Altai Mountains
The Altai Mountains (), also spelled Altay Mountains, are a mountain range in Central Asia, Central and East Asia, where Russia, China, Mongolia and Kazakhstan converge, and where the rivers Irtysh and Ob River, Ob have their headwaters. The m ...
of
Mongolia
Mongolia; Mongolian script: , , ; lit. "Mongol Nation" or "State of Mongolia" () is a landlocked country in East Asia, bordered by Russia to the north and China to the south. It covers an area of , with a population of just 3.3 million, ...
in the northeast, and the
Heavenly Mountains (Tian Shan) in the south.
The geology of Junggar Basin mainly consists of
sedimentary rock
Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...
s underlain by
igneous
Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or ...
and
metamorphic
Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock (protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, causin ...
basement rocks.
The basement of the basin was largely formed during the development of the
Pangea
Pangaea or Pangea () was a supercontinent that existed during the late Paleozoic and early Mesozoic eras. It assembled from the earlier continental units of Gondwana, Euramerica and Siberia during the Carboniferous approximately 335 million y ...
supercontinent during complex tectonic events from
Precambrian
The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the ...
to late
Paleozoic
The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon.
The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838
by combining the Greek words ''palaiós'' (, "old") and ' ...
time.
The basin developed as a series of
foreland basin
A foreland basin is a structural basin that develops adjacent and parallel to a mountain belt. Foreland basins form because the immense mass created by crustal thickening associated with the evolution of a mountain belt causes the lithospher ...
s – in other words, basins developing immediately in front of growing mountain ranges – from
Permian
The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleoz ...
time to the
Quaternary
The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from 2.58 million years ...
period.
The basin's preserved sedimentary records show that the climate during the
Mesozoic
The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceo ...
era was marked by a transition from humid to arid conditions as monsoonal climatic effects waned.
The Junggar basin is rich in geological resources (e.g.
petroleum
Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crud ...
,
coal
Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen.
Coal is formed when dea ...
and
ore deposits
Ore is natural rock or sediment that contains one or more valuable minerals, typically containing metals, that can be mined, treated and sold at a profit.Encyclopædia Britannica. "Ore". Encyclopædia Britannica Online. Retrieved 7 April 2 ...
) due to effects of
volcanism
Volcanism, vulcanism or volcanicity is the phenomenon of eruption of molten rock (magma) onto the surface of the Earth or a solid-surface planet or moon, where lava, pyroclastics, and volcanic gases erupt through a break in the surface called ...
and sedimentary deposition.
Regional tectonic setting
![Junggar basin map(3)](https://upload.wikimedia.org/wikipedia/commons/7/70/Junggar_basin_map%283%29.png)
The major structural components of the Junggar Basin divided into six parts:
# Wulungu Depression were formed by
faulting
In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...
and flat
depression. There was about 2,000 – 4,000 m thick sedimentary layers that deposited from
Permian
The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleoz ...
to the present.
# Luliang uplift (Sangequan uplift) was surrounded by narrow but steeply dipping at the north and wide but gently dipping at the south. There were about 1,100 – 4,000 m thick sedimentary layers and the complete layer from Permian to the present can be found in the southern part. Also, the
plunging fold was found in this area.
# Central Depression was formed by three major lowland plains where are in Manas, Central, and Wucaiwan. There were 5,000 m thick sedimentary layers from
Carboniferous
The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonifero ...
to
Quaternary
The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from 2.58 million years ...
.
# West Uplift consists of Chepaizi-Paotai uplift and Urho-Karamay monocline.
#* Chepaizi-Paotai uplift formed by eastward plunging fold with faulting. The
footwall
In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...
includes Jurassic-Quaternary sedimentary layers while the
hanging wall
In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...
consists of post-Carboniferous sedimentary layers.
#* Urho-Karamay monocline was formed with
thrust fault
A thrust fault is a break in the Earth's crust, across which older rocks are pushed above younger rocks.
Thrust geometry and nomenclature
Reverse faults
A thrust fault is a type of reverse fault that has a dip of 45 degrees or less.
If ...
along the west-northwest boundary of the basin.
The
Indo-Australian plate
The Indo-Australian Plate is a major tectonic plate that includes the continent of Australia and the surrounding ocean and extends northwest to include the Indian subcontinent and the adjacent waters. It was formed by the fusion of the Indian an ...
collision during Neogene resulted in uplift of the northern Junggar basin. This also resulted in re-activation of Permian
thrust fault
A thrust fault is a break in the Earth's crust, across which older rocks are pushed above younger rocks.
Thrust geometry and nomenclature
Reverse faults
A thrust fault is a type of reverse fault that has a dip of 45 degrees or less.
If ...
s,
produced faults on basement rocks and rifting on basin margin to form Karamay-Urho
monocline
A monocline (or, rarely, a monoform) is a step-like fold in rock strata consisting of a zone of steeper dip within an otherwise horizontal or gently-dipping sequence.
Formation
Monoclines may be formed in several different ways (see diagram)
* ...
. This area concentrated abundant hydrocarbons on the
anticline
In structural geology, an anticline is a type of fold that is an arch-like shape and has its oldest beds at its core, whereas a syncline is the inverse of an anticline. A typical anticline is convex up in which the hinge or crest is the ...
part.
# East Uplift (Zhangpenggou-Qitai uplift) was formed by
deformations in several times. The formation of NE-trend plunging fold in this area activated the faulting of basement rocks.
# Tian Shan Foredeep formed during lower-middle Triassic since the Tian Shan has uplifted continuously.
During Cretaceous, the basin sank again and thus water depth became shallow due to tectonic deformations.
In Paleogene, the size of the lake kept reducing and the eastern basin become a landmass. Also, there was further subsidence of Tian Shan Foredeep because of the formation of Himalayan in Paleogene.
Geology
Basement rock of Junggar Basin
In
Precambrian
The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the ...
section was made up of
felsic
In geology, felsic is a modifier describing igneous rocks that are relatively rich in elements that form feldspar and quartz.Marshak, Stephen, 2009, ''Essentials of Geology,'' W. W. Norton & Company, 3rd ed. It is contrasted with mafic rocks, whi ...
-
intermediate granite
Granite () is a coarse-grained (phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies undergro ...
with the inclusion of
greenstones and
ophiolite
An ophiolite is a section of Earth's oceanic crust and the underlying upper mantle that has been uplifted and exposed above sea level and often emplaced onto continental crustal rocks.
The Greek word ὄφις, ''ophis'' (''snake'') is found i ...
s, where the Paleozoic section consists of mainly potassium- and sodium-deficient
extrusive rock
Extrusive rock refers to the mode of igneous volcanic rock formation in which hot magma from inside the Earth flows out (extrudes) onto the surface as lava or explodes violently into the Earth's atmosphere, atmosphere to fall back as Pyroclastic ...
s.
The
basalt
Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...
s in the basement which indicated trapped late Paleozoic oceanic crust that came from the mantle.
Sedimentary stratigraphy
The sedimentary
facies
In geology, a facies ( , ; same pronunciation and spelling in the plural) is a body of rock with specified characteristics, which can be any observable attribute of rocks (such as their overall appearance, composition, or condition of formatio ...
started to be dominant in Permian. The layers continuously deposited fluvial and lacustrine facies until the present day, mostly containing conglomerate, sandstone, siltstone, and mudstone.
Major stratigraphic units in the Junggar basin from Carboniferous are shown in ascending order in the following table:
Paleoclimate and environment
Throughout Mesozoic, Junggar Basin was mainly in the fluvial and lake depositional environment.
The climate in the late Permian showed the fluctuation between dry- or wet-dominated climate. The pieces of evidence included the presence of both organic beds and red beds. In the early Triassic,
reddish
Reddish is an area in Metropolitan Borough of Stockport, Greater Manchester, England. south-east of Manchester city centre. At the 2011 Census, the population was 28,052. Historically part of Lancashire, Reddish grew rapidly in the Industrial ...
sedimentary rocks formed that indicated the dominance of
semi-arid climate
A semi-arid climate, semi-desert climate, or steppe climate is a dry climate sub-type. It is located on regions that receive precipitation below potential evapotranspiration, but not as low as a desert climate. There are different kinds of semi-ar ...
.
During Late Triassic-Early Jurassic, the Junggar basin was in a warm and wet climate due to the effect of continental
monsoon
A monsoon () is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with annual latitudinal oscil ...
al climate.
From middle to late Jurassic, the climate shifted as a seasonal arid climate that initiated from the northeast and then widespread to the whole basin.
This is because the
Pangea
Pangaea or Pangea () was a supercontinent that existed during the late Paleozoic and early Mesozoic eras. It assembled from the earlier continental units of Gondwana, Euramerica and Siberia during the Carboniferous approximately 335 million y ...
started to break apart that halted the effect from the mega-monsoon system.
Therefore, the basin became affected by
westerlies
The westerlies, anti-trades, or prevailing westerlies, are prevailing winds from the west toward the east in the middle latitudes between 30 and 60 degrees latitude. They originate from the high-pressure areas in the horse latitudes and trend to ...
.
The westerlies contained the lesser moisture that has come from the northwest since the marine areas gradually minimized to the recent
Caspian Sea
The Caspian Sea is the world's largest inland body of water, often described as the world's largest lake or a full-fledged sea. An endorheic basin, it lies between Europe and Asia; east of the Caucasus, west of the broad steppe of Central Asia ...
.
With the continuous uplift along the
Tian Shan
The Tian Shan,, , otk, 𐰴𐰣 𐱅𐰭𐰼𐰃, , tr, Tanrı Dağı, mn, Тэнгэр уул, , ug, تەڭرىتاغ, , , kk, Тәңіртауы / Алатау, , , ky, Теңир-Тоо / Ала-Тоо, , , uz, Tyan-Shan / Tangritog‘ ...
, the orographic effect around the basin intensifies the
rain-shadow effect.
The prominent rain-shadow effect results in a warmer seasonal arid climate in the basin.
At the same time, the lakes in the basin had higher salinity and lower sedimentation influx.
Tectonic evolution
Pre-Permian (before 290 Ma): basement rock evolution
Xinjiang paleocraton was pulled apart for a continental rifting episode to form extensional basins in Late
Cambrian
The Cambrian Period ( ; sometimes symbolized C with bar, Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million ...
.
The continuous divergence of the continental crust during late Cambrian to
Ordovician
The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start ...
shaped the West Junggar Ocean.
The West Junggar Ocean presented as the present Tangbale and Honguleleng ophiolites from intra-plate volcanism, and then this volcanism shut in mid-upper Ordovician.
The Ordovician first
ocean basin
In hydrology, an oceanic basin (or ocean basin) is anywhere on Earth that is covered by seawater. Geologically, ocean basins are large geologic basins that are below sea level.
Most commonly the ocean is divided into basins foll ...
indicated that eastern Junggar was over
passive margin
A passive margin is the transition between oceanic and continental lithosphere that is not an active plate margin. A passive margin forms by sedimentation above an ancient rift, now marked by transitional lithosphere. Continental rifting creat ...
.
Another rifting event established the Mayilashan ocean basin and
back-arc basin
A back-arc basin is a type of geologic basin, found at some convergent plate boundaries. Presently all back-arc basins are submarine features associated with island arcs and subduction zones, with many found in the western Pacific Ocean. Most of ...
in east Junggar during
Silurian
The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozo ...
.
However, the compressional environment restricted the two landforms so that they ended up shut and folded in the late Silurian.
This eventually led to the convergence of
Tarim,
Kazakhstan
Kazakhstan, officially the Republic of Kazakhstan, is a transcontinental country located mainly in Central Asia and partly in Eastern Europe. It borders Russia to the north and west, China to the east, Kyrgyzstan to the southeast, Uzbeki ...
and
Siberian
Siberia ( ; rus, Сибирь, r=Sibir', p=sʲɪˈbʲirʲ, a=Ru-Сибирь.ogg) is an extensive region, geographical region, constituting all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has been a ...
paleo-plates.
They were from the original Xinjiang paleocraton that puzzled each other again.
Junggar Ocean and Kulumudi Ocean were produced from the third rifting event during lower-mid
Devonian
The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...
.
Eventually, the Junggar ocean and Kulumudi Ocean moved towards the north and undergone the subduction from upper Devonian to Late-
Carboniferous
The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonifero ...
.
At the same time, several
volcanic arc
A volcanic arc (also known as a magmatic arc) is a belt of volcanoes formed above a subducting oceanic tectonic plate,
with the belt arranged in an arc shape as seen from above. Volcanic arcs typically parallel an oceanic trench, with the arc lo ...
s were developed during subduction.
Three plates (Tarim, Kazakhstan, and Siberian) converged together to form a trapped ocean that surrounded volcanic arc and orogens in Mid-Carboniferous.
Alkali-rich
granite
Granite () is a coarse-grained (phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies undergro ...
s with gold deposits intruded the converged plates.
This revealed the partial melting of the oceanic crust.
This also marked as the last subduction event following the post-collisional stage in Late-Carboniferous.
Besides, Such intrusive rocks demonstrated that this was the last melting episode of oceanic crust.
As part of the Eurasian plate started to combine continental crusts for the three plates, to consolidate them as another modern
stable continental block.
Underplating events
The mafic-ultramafic igneous rocks formed due to
underplating
Magmatic underplating occurs when basaltic magmas are trapped during their rise to the surface at the Mohorovičić discontinuity or within the Crust (geology), crust. Entrapment (or 'stalling out') of magmas within the crust occurs due to the dif ...
with crustal stretching during Carboniferous to Permian.
The magma underplating during Carboniferous to Permian (330-250 Ma) period heated up the lower crust and thus the crust got hotter. The following cooling crustal episode led to part of the mountain belt sink by
thermal subsidence In geology and geophysics, thermal subsidence is a mechanism of subsidence in which conductive cooling of the mantle thickens the lithosphere and causes it to decrease in elevation. This is because of thermal contraction: as mantle material cools a ...
, which ended up forming the Junggar Basin.
Another magma underplating event occurred in the Mesozoic era.
This was forming heterogenic silica-rich igneous rocks due to the partial melting of numerous oceanic crusts contaminated with
mantle wedge
A mantle wedge is a triangular shaped piece of mantle that lies above a subducting tectonic plate and below the overriding plate. This piece of mantle can be identified using seismic velocity imaging as well as earthquake maps. Subducting oceanic ...
.
Permian to Present (From 290 Ma): Junggar Basin evolution
With the influence of
Variscan orogeny
The Variscan or Hercynian orogeny was a geologic mountain-building event caused by Late Paleozoic continental collision between Euramerica (Laurussia) and Gondwana to form the supercontinent of Pangaea.
Nomenclature
The name ''Variscan'', comes f ...
, Early Permian marine facies changed into the
terrestrial environment during Late Permian.
This is because orogenic compression and crustal thickening resulted in higher sedimentation and withdrawn of the sea.
At that time, widespread uplift occurred with
subsidence
Subsidence is a general term for downward vertical movement of the Earth's surface, which can be caused by both natural processes and human activities. Subsidence involves little or no horizontal movement, which distinguishes it from slope move ...
formed a
graben
In geology, a graben () is a depressed block of the crust of a planet or moon, bordered by parallel normal faults.
Etymology
''Graben'' is a loan word from German, meaning 'ditch' or 'trench'. The word was first used in the geologic contex ...
at first.
Then, the area gradually became a mountain-trapped peripheral
foreland basin
A foreland basin is a structural basin that develops adjacent and parallel to a mountain belt. Foreland basins form because the immense mass created by crustal thickening associated with the evolution of a mountain belt causes the lithospher ...
due to high-temperature and relaxing subsidence from the regional extension.
Some also suggested this landform caused by the combined effect of shearing and extension or thrusting from crustal shortening.
Starting from Permian, Junggar Basin was formed to initiate the foreland basin cycle.
There presented extensional shearing and continuous deposition of
non-marine foreland basin-fill till
Triassic
The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...
.
Since the level of the trapped lake in the basin was rising, finer deposits covered widespread the basin with
denudation
Denudation is the geological processes in which moving water, ice, wind, and waves erode the Earth's surface, leading to a reduction in elevation and in relief of landforms and landscapes. Although the terms erosion and denudation are used interch ...
.
This also marked as the end of the foreland basin cycle.
From Jurassic to
Palaeogene
The Paleogene ( ; also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period million years ago ( Mya) to the beginning o ...
, the Junggar Basin undergone intra-continental depression. There was covered in braided delta with few lakes and increasing subsidence rate towards the south from 20 to 120 m/Ma during Jurassic.
The collision of the Lhasa block from the south resulted that the delta formed along the margin of the basin.
Also, the deeper lake was at the basin centre during Lower
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...
.
Afterward, the southward lake depression leading the basin centre shift to the south in the Upper Cretaceous period.
In Paleogene, braid-delta developed over the basin where sediments entered from the mountains of the surrounding basin.
Starting from
Neogene
The Neogene ( ), informally Upper Tertiary or Late Tertiary, is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period million years ago ( Mya) to the beginning of the present Quaternary Period Mya. ...
, the thrust fault in the Junggar Basin was reactivated.
At the same time, there was rapid uplift of Tian Shan since
Himalayan orogeny
The geology of the Himalayas is a record of the most dramatic and visible creations of the immense mountain range formed by plate tectonic forces and sculpted by weathering and erosion. The Himalayas, which stretch over 2400 km between th ...
formed by the collision between
Indo-plate and
Eurasian Plate
The Eurasian Plate is a tectonic plate that includes most of the continent of Eurasia (a landmass consisting of the traditional continents of Europe and Asia), with the notable exceptions of the Indian subcontinent, the Arabian subcontinent and ...
.
This developed an alluvial-rich delta system around shallow lakes with the clastic sediments influx from uplifted Tian Shan and the northern part of the basin.
Geological resources
Petroleum system
Junggar Basin contains the third-largest
petroleum reservoir
A petroleum reservoir or oil and gas reservoir is a subsurface accumulation of hydrocarbons contained in porous or fractured rock formations.
Such reservoirs form when kerogen (ancient plant matter) is created in surrounding rock by the presence ...
s in China.
About two-thirds of oil can be found in the Karamay-Urho monocline area.
There was formed in Carboniferous deep-sea sedimentary rocks and lake sedimentary layers from Permian to Tertiary.
For Carboniferous oil and gas deposits in this area, they were moved upward and accumulated in the Permian period and Mesozoic era
sandstone
Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks.
Most sandstone is composed of quartz or feldspar (both silicates) ...
s.
Then, the layers altered as the
structural trap
In petroleum geology, a trap is a geological structure affecting the reservoir rock and caprock of a petroleum system allowing the accumulation of hydrocarbons in a reservoir. Traps can be of two types: stratigraphic or structural. Structural trap ...
locations by tectonic activities in the later stage.
Petroleum
Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crud ...
is dominant in
Karamay
Karamay is a prefecture-level city in the north of the Xinjiang Uyghur Autonomous Region, People's Republic of China. The name of the city comes from the Uyghur language and means "black oil", referring to the oil fields near the city.
Karamay w ...
, Baikouquan, Urho,
Dushanzi, and
Qigu.
The oil and gas fields can be found on Tertiary Dushanzi sandstone.
Besides, gas fields are found in the Karamay as well as the inland region of the basin.
Besides, Tian Shan Foredeep in the southern Junggar Basin (including
Urumqi) is also available for the petroleum resources.
The petroleum there were formed due to rapid subsidence, regional
ductile with mobile intrusion, and cross-cutting on anticlines by orogenic activity (probably in Neogene) from the Tian Shan.
Part of the oil-bearing sedimentary rocks was deposited in the
salty oxygen-deficient lake environment during Permian.
The crude oil in this sedimentary rocks formed by remains of algae and humus.
Coal
Bituminous coal
Bituminous coal, or black coal, is a type of coal containing a tar-like substance called bitumen or asphalt. Its coloration can be black or sometimes dark brown; often there are well-defined bands of bright and dull material within the seams. It ...
was found in Tian Shan Foredeep.
It was deposited in the lake or
swamp
A swamp is a forested wetland.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p. Swamps are considered to be transition zones because both land and water play a role in ...
environment in the Early to Middle Jurassic periods.
For example, Badaowan, Sangonghe, and Xishanyao Formation.
About 18 gigatonnes of coal can be recovered in Tian Shan Foredeep.
Apart from Tian Shan Foredeep, the coal can be found in the base of alluvial fan and nearby the margin of lakes in the eastern and western margin of Junggar Basin.
Ore deposits
Ore deposits
Ore is natural rock or sediment that contains one or more valuable minerals, typically containing metals, that can be mined, treated and sold at a profit.Encyclopædia Britannica. "Ore". Encyclopædia Britannica Online. Retrieved 7 April 2 ...
in the Junggar Basin were mainly formed in the Paleozoic era which was related to tectonic development.
The followings are the available ore deposits in Junggar Basin:
*
Porphyry copper-gold deposits found in the west and northeast of the Junggar Basin.
*
Iron
Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...
deposits found in the eastern part of the basin due to early subduction events during Lower Carboniferous.
* During post-collision extensional events in Permian,
gold
Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile met ...
deposits found on the west side and tin deposits found on the east side.
See also
*
Dzungaria
Dzungaria (; from the Mongolian language, Mongolian words , meaning 'left hand') is a geographical subregion in Northwest China that corresponds to the northern half of Xinjiang. It is thus also known as Beijiang, which means "Northern Xinjiang" ...
References
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Geology of Xinjiang
Sedimentary basins of Asia