Coal Bed Methane

Coal Bed Natural Gas (CBNG), or Coal Bed Methane (CBM), wells produce gas from the coal seams which act as both the source and the reservoir. Natural gas can be sourced by thermogenic alterations of coal or by biogenic action of indigenous microbes on the coal. There are some horizontally drilled CBM wells and some that receive hydraulic fracturing treatments. However, wells frequently produce water as well as natural gas. Some CBM reservoirs are also underground sources of drinking water and, as such, there are restrictions on hydraulic fracturing. CBM reservoirs are mostly shallow as the coal matrix does not have the strength to maintain porosity under the pressure of significant overburden thickness. CBM plays also provide a very good means of CO2 sequestration because CO2 molecules displace CH4 methane molecules on the face of the coal, generating greater methane production while sequestering the CO2 in the coal bed.

MICROFOSSILS

Microfossils are important to paleontology in a number of ways. They facilitate in dating other fossils, help put together a portrait of an ancient environment, and even have importance in the oil and mining industries. And since they are usually found in huge clusters within sedimentary rocks, microfossils are by far the most abundant of biological, fossilized remains.


What are Microfossils?
In general, microfossils are the miniscule remains of protists, fungi, bacteria, plants, and animals. This seems like a very diverse grouping, and it really is. Microfossils are not grouped together according to their relationships to one another, but are categorized as such only because of their tiny size. They are generally no larger than four millimeters.




Types of Microfossils:-
Protists and prokaryotes (organisms lacking cell nuclei, among other things) are the oldest, and the most multitudinous of the microfossil subgroup. Protists and prokaryotes, mostly single-celled remains, were the only living organisms on Earth for most of life’s history, so their numbers are understandable. These organisms greatly assist in the studies of early evolution.

Ostracods, shrimp-like crustaceans, are the most advanced forms of full-organism microfossils studied. They are bean shaped, and their shells are calcitic, so they fossilize well. When one of these crustaceans dies, their bodies decompose, leaving their calcium-rich shells behind.

The rest of the field of study is comprised of small fossilized remains of animals, plants, and various types of fungi. The fossilized fungi are often found within larger plant fossils, but are generally abundant and often ignored by paleontologists because of their relationship with plants. As for animals, all creatures with bones or calcium-rich skeletons have heartily contributed to the study of microfossils.

How are Microfossils Useful?
The most immediately significant use of microfossils is their ability to assist in age-dating the rocks in which they are found. And since they are so abundant - found in many types of sedimentary rocks – they are particularly useful.

Not only can they date their fossilized environment, but microfossils can also tell paleontologists a great deal about the types of environments in which they once lived. For instance, most of the single-celled microfossils found once lived in water, and their fossils can be great indicators of water depth. Some types of ostracods, which are often marine creatures, can give some hints of salinity.

Microfossils have played a big part in the current climate change studies as scientists struggle to record ancient temperatures in order to compare. Once again because of their abundance, they offer a good indicator of climate change over a specified period of time, depending on the fossils collected.

geology of western ghat

The Western Ghats are not true mountains, but are the faulted edge of the Deccan Plateau. They are believed to have been formed during the break-up of the super continent of Gondwana some 150 million years ago[citation needed]. Geophysicists Barren and Harrison from the University of Miami advocate the theory that the west coast of India came into being somewhere around 100 to 80 mya after it broke away from Madagascar. After the break-up, the western coast of India would have appeared as an abrupt cliff some 1,000 meters in height[citation needed]. Soon after its detachment, the peninsular region of the Indian plate drifted over the Réunion hotspot, a volcanic hotspot in the Earth's lithosphere near the present day location of Réunion[citation needed]. A huge eruption here some 65 mya[citation needed] is thought to have laid down the Deccan Traps, a vast bed of basalt lava that covers parts of central India. These volcanic upthrusts led to the formation of the northern third of the Western Ghats. These dome-shaped uplifts expose underlying 200 mya[citation needed] rocks observed in some parts such as the Nilgiri Hills. Basalt is the predominant rock found in the hills reaching a depth of 3 km (2 mi). Other rock types found are charnockites, granite gneiss, khondalites, leptynites, metamorphic gneisses with detached occurrences of crystalline limestone, iron ore, dolerites and anorthosites. Residual laterite and bauxite ores are also found in the southern hills.

Ultramafic rock

Ultramafic (also referred to as ultrabasic) rocks are igneous and meta-igneous rocks with very low silica content (less than 45%), generally >18% MgO, high FeO, low potassium, and are composed of usually greater than 90% mafic minerals (dark colored, high magnesium and iron content). The Earth's mantle is considered to be composed of ultramafic rocks.

Intrusive ultramafic rocks are often found in large, layered ultramafic intrusions where differentiated rock types often occur in layers[1]. Such cumulate rock types do not represent the chemistry of the magma from which they crystallized. The ultramafic intrusives include the dunites, peridotites and pyroxenites. Other rare varieties include troctolite which has a greater percentage of calcic plagioclase. These grade into the anorthosites. Gabbro and norite often occur in the upper portions of the layered ultramafic sequences. Hornblendite and, rarely phlogopitite are also found.

Volcanic ultramafic rocks are rare outside of the Archaean and are essentially restricted to the Neoproterozoic or earlier, although some boninite lavas currently erupted within back-arc basins (Manus Trough, New Guinea) verge on being ultramafic. Subvolcanic ultramafic rocks and dykes persist longer, but are also rare. Many of the lavas being produced on Io may be ultramafic, as evidenced by their temperatures which are higher than terrestrial mafic eruptions.

Examples include komatiite[2] and picritic basalt. Komatiites can be host to ore deposits of nickel[3].
Metamorphism of ultramafic rocks in the presence of water and/or carbon dioxide results in two main classes of metamorphic ultramafic rock; talc carbonate and serpentinite.

Talc carbonation reactions occur in ultramafic rocks at lower greenschist through to granulite facies metamorphism when the rock in question is subjected to metamorphism and the metamorphic fluid has more than 10% molar proportion of carbon dioxide.

When the metamorphic fluids in contact with the ultramafic rock have less than 10% CO2 the metamorphic reactions favor serpentinisation reactions, resulting in chlorite-serpentine-amphibole type assemblages



Ultramafic rock types: Peridotite, dunite, norite, essexite, komatiite.
Cumulate rocks and rock types: chromitite, magnetite, anorthosite
Ultramafic-associated ore deposits: Lateritic nickel ore deposits, kambalda type komatiitic nickel ore deposits, diamond
Kimberlite, lamproite, lamprophyre

Mineral exploration

Mineral exploration is the process undertaken by companies, partnerships or corporations in the endeavour of finding ore (commercially viable concentrations of minerals) to mine. Mineral exploration is a much more intensive, organised and professional form of mineral prospecting and, though it frequently uses the services of prospecting, the process of mineral exploration on the whole is much more 3.involved.

Stages of mineral exploration
1. Area selection
2. Target definition or generation
3. Resource evaluation
4. Reserve definition
5. Extraction

Factors that Control Metamorphism

Metamorphism occurs because some minerals are stable only under certain conditions of pressure and temperature. When pressure and temperature change, chemical reactions occur to cause the minerals in the rock to change to an assemblage that is stable at the new pressure and temperature conditions. But, the process is complicated by such things as how the pressure is applied, the time over which the rock is subjected to the higher pressure and temperature, and whether or not there is a fluid phase present during metamorphism.

Temperature


Temperature increases with depth in the Earth along the Geothermal Gradient. Thus higher temperature can occur by burial of rock.


Temperature can also increase due to igneous intrusion.


Pressure increases with depth of burial, thus, both pressure and temperature will vary with depth in the Earth. Pressure is defined as a force acting equally from all directions. It is a type of stress, called hydrostatic stress, or uniform stress. If the stress is not equal from all directions, then the stress is called a differential stress. If differential stress is present during metamorphism, it can have a profound effect on the texture of the rock.

rounded grains can become flattened in the direction of maximum stress.

minerals that crystallize or grow in the differential stress field can have a preferred orientation. This is especially true of the sheet silicate minerals (the micas: biotite and muscovite, chlorite, talc, and serpentine).

These sheet silicates will grow with their sheets orientated perpendicular to the direction of maximum stress. Preferred orientation of sheet silicates causes rocks to be easily broken along approximately parallel sheets. Such a structure is called a foliation.

Fluid Phase - Any existing open space between mineral grains in a rocks can potentially contain a fluid. This fluid is mostly H2O, but contains dissolved mineral matter. The fluid phase is important because chemical reactions that involve one solid mineral changing into another solid mineral can be greatly speeded up by having dissolved ions transported by the fluid. Within increasing pressure of metamorphism, the pore spaces in which the fluid resides is reduced, and thus the fluid is driven off. Thus, no fluid will be present when pressure and temperature decrease and, as discussed earlier, retrograde metamorphism will be inhibited.


Time - The chemical reactions involved in metamorphism, along with recrystallization, and growth of new minerals are extremely slow processes. Laboratory experiments suggest that the longer the time available for metamorphism, the larger are the sizes of the mineral grains produced. Thus, coarse grained metamorphic rocks involve long times of metamorphism. Experiments suggest that the time involved is millions of years.


Types of Metamorphism

Cataclastic Metamorphism - This type of metamorphism is due to mechanical deformation, like when two bodies of rock slide past one another along a fault zone. Heat is generated by the friction of sliding along the zone, and the rocks tend to crushed and pulverized due to the sliding. Cataclastic metamorphism is not very common and is restricted to a narrow zone along which the sliding occurred.


Burial Metamorphism - When sedimentary rocks are buried to depths of several hundred meters, temperatures greater than 300oC may develop in the absence of differential stress. New minerals grow, but the rock does not appear to be metamorphosed. The main minerals produced are the Zeolites. Burial metamorphism overlaps, to some extent, with diagenesis, and grades into regional metamorphism as temperature and pressure increase.


Contact Metamorphism - Occurs adjacent to igneous intrusions and results from high temperatures associated with the igneous intrusion. Since only a small area surrounding the intrusion is heated by the magma, metamorphism is restricted to a zone surrounding the intrusion, called a metamorphic aureole. Outside of the contact aureole, the rocks are unmetamorphosed. The grade of metamorphism increases in all directions toward the intrusion. Because temperature differences between the surrounding rock and the intruded magma are larger at shallow levels in the crust, contact metamorphism is usually referred to as high temperature, low pressure metamorphism. The rock produced is often a fine-grained rock that shows no foliation, called a hornfels.

The word "Metamorphism" comes from the Greek: Meta = change, Morph = form, so metamorphism means to change form. In geology this refers to the changes in mineral assemblage and texture that result from subjecting a rock to pressures and temperatures different from those under which the rock originally formed.

Note that Diagenesis is also a change in form that occurs in sedimentary rocks. In geology, however, we restrict diagenetic processes to those which occur at temperatures below 200oC and pressures below about 300 MPa (MPa stands for Mega Pascals), this is equivalent to about 3,000 atmospheres of pressure.


Metamorphism, therefore occurs at temperatures and pressures higher than 200oC and 300 MPa. Rocks can be subjected to these higher temperatures and pressures as they become buried deeper in the Earth. Such burial usually takes place as a result of tectonic processes such as continental collisions or subduction.


The upper limit of metamorphism occurs at the pressure and temperature of wet partial melting of the rock in question. Once melting begins, the process changes to an igneous process rather than a metamorphic process.
Grade of Metamorphism
As the temperature and/or pressure increases on a body of rock we say that the rock undergoes prograde metamorphism or that the grade of metamorphism increases. Metamorphic grade is a general term for describing the relatLow-grade metamorphism takes place at temperatures between about 200 to 320oC, and relatively low pressure. Low grade metamorphic rocks are characterized by an abundance of hydrous minerals (minerals that contain water, H2O, in their crystal structure).

Examples of hydrous minerals that occur in low grade metamorphic rocks:


Clay Minerals


Serpentine


Chlorite

High-grade metamorphism takes place at temperatures greater than 320oC and relatively high pressure. As grade of metamorphism increases, hydrous minerals become less hydrous, by losing H2O and non-hydrous minerals become more common.

Examples of less hydrous minerals and non-hydrous minerals that characterize high grade metamorphic rocks:

Muscovite - hydrous mineral that eventually disappears at the highest grade of metamorphism


Biotite - a hydrous mineral that is stable to very high grades of metamorphism.


Pyroxene - a non hydrous mineral.


Garnet - a non hydrous mineral.

ive temperature and pressure conditions under which metamorphic rocks form.
Retrograde Metamorphism
As temperature and pressure fall due to erosion of overlying rock or due to tectonic uplift, one might expect metamorphism to a follow a reverse path and eventually return the rocks to their original unmetamorphosed state. Such a process is referred to as retrograde metamorphism. If retrograde metamorphism were common, we would not commonly see metamorphic rocks at the surface of the Earth. Since we do see metamorphic rocks exposed at the Earth's surface retrograde metamorphism does not appear to be common. The reasons for this include:

chemical reactions take place more slowly as temperature is decreased


during prograde metamorphism, fluids such as H2O and CO2 are driven off, and these fluids are necessary to form the hydrous minerals that are stable at the Earth's surface.


chemical reactions take place more rapidly in the presence of fluids, but if the fluids are driven off during prograde metamorphism, they will not be available to speed up reactions during retrograde metamorphism.