July 2014

High-Sulphidation Deposits of Gold

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High-sulphidation deposits result from fluids (dominantly gases such as SO2, HF, HCl) channeled directly from a hot magma. The fluids interact with groundwater and form strong acids. These acids rot and dissolve the surrounding rock leaving only silica behind, often in a sponge-like formation known as vuggy silica. Gold and sometimes copper-rich brines that also ascend from the magma then precipitate their metals within the spongy vuggy silica bodies. The shape of these mineral deposits is generally determined by the distribution of vuggy silica. Sometimes the vuggy silica can be widespread if the acid fluids encountered a broad permeable geologic unit. In this case it is common to find large bulk-tonnage mines with lower grades.<br>
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The acidic fluids are progressively neutralized by the rock the further they move away from the fault. The rocks in turn are altered by the fluids into progressively more neutral-stable minerals the further away from the fault. As a result, definable zones of alteration minerals are almost always are formed in shell-like layers around the fault zone.<br>
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Typically the sequence is to move from vuggy silica (the centre of the fault) progressing through quartz-alunite to kaolinite-dickite, illite rich rock, to chlorite rich rock at the outer reaches of alteration. Alunite (a sulphate mineral) and kalonite, dickite, illite and chlorite (clay minerals) are generally whitish to yellowish in colour. The clay and sulphate alteration (referred to as acid-sulphate alteration) in high-sulphidation systems can leave huge areas, sometimes up to 100 square kilometers of visually impressive coloured rocks.<br>
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<span style="color: blue;"><span style="background-color: white; color: #ff6600; font-family: "verdana"; font-size: 12px; font-weight: bold; line-height: 16px;">ALTERATION IN A HIGH-SULPHIDATION SYSTEM:</span></span></div>
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In contrast, low-sulphidation veins are formed when the fluids interact with greater amounts of groundwater as they rise from the hot magma. The protracted boiling of the fluids in low-sulphidation systems produces high grade gold (greater than one ounce gold per ton) and silver deposits. The fluids interact with the surrounding rock for a much longer period of time than the quickly channeled high-sulphidation fluids. As a result, the fluids become dilute and<br>
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neutralized and the silica dissolves. The silica is later precipitated in the veins as quartz, often sealing the fissure closed. When this occurs, the pressure of the gases underneath the sealed fault builds until the seal is ruptured, which provokes catastrophic boiling and the precipitation of gold.<br>
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After this explosive boiling event, passive conditions return, and quartz precipitates once again. This cyclical process results in the well-known banded texture of the quartz-adularia veins typical of low-sulphidation vein systems. Quartz-adularia veins can contain high-grade gold (greater than one ounce gold per ton) and silver deposits, over vertical intervals of generally 300 to 600 metres. Within this vertical dimension, high gold grades can make for a large amount of easy to mine gold in a narrow compact area.<br>
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<span style="color: blue;"><span style="background-color: white; color: #ff6600; font-family: "verdana"; font-size: 12px; font-weight: bold; line-height: 16px;">ALTERATION IN A HIGH-SULPHIDATION SYSTEM:</span></span><br>
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High-Sulphidation Deposits of Gold

High-sulphidation deposits result from fluids (dominantly gases such as SO2, HF, HCl) channeled directly from a hot magma. The flui...

Epithermal Systems: The Association of Gold Mineralization With Volcanic

edu, Gold, Tectonic, volcano 9:52 PM

Epithermal Systems: The Association of Gold Mineralization With Volcanic

The association of gold mineralization with volcanic and geothermal hot spring activity has long been recognized by prospectors and geologi...

Green balls of conichalcite with erythrite, brown olivenite

Minerals 11:41 PM

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<span style="font-family: Georgia,"Times New Roman",serif;">Erythrite : Co3(AsO4)2·8H2O, Olivenite : Cu2(AsO4)(OH), Conichalcite : CaCu(AsO4)(OH)</span><br />
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<span style="font-family: Georgia,"Times New Roman",serif;">Locality: La Cena del Depósito concession, Cerro Minado Mines, Cuesta Alta, Huércal-Overa, Almería, Andalusia, Spain</span><br />
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<span style="font-family: Georgia,"Times New Roman",serif;">Green balls of conichalcite with erythrite, brown olivenite</span><br />
<span style="font-family: Georgia,"Times New Roman",serif;"><br /></span><span style="font-family: Georgia,"Times New Roman",serif;">Photo & Collection IOB Sylvano</span></div>

Green balls of conichalcite with erythrite, brown olivenite

Erythrite : Co3(AsO4)2·8H2O, Olivenite : Cu2(AsO4)(OH), Conichalcite : CaCu(AsO4)(OH) Locality: La Cena del Depósito concession, Cerr...

The Difference Between Rocks and Minerals

Igneous, Metamorphic, Mineralogy, Rocks, sedimentary 7:00 PM

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<b>A mineral</b> is a solid formation that occurs naturally in the earth while a rock is a solid combination of more than one mineral formations which is also occurring naturally.</div>
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A mineral has a unique chemical composition and is necessarily defined by its crystalline structure and shape. On the other hand, since a rock can be composed of several minerals it is classified according to the process of its formation. A rock can also contain organic remains and mineraloids apart from regular mineral formations. There are some rocks that may include just one mineral formation though.</div>
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The commercial value of minerals is immense and rocks are mined to extract these minerals. Such rocks are known as ores and the residue of the rock after the mineral has been extracted is called tailing.</div>
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The classification of rocks also depends on their mineral and chemical composition, texture and the process of formation. Rocks are therefore classified as igneous, sedimentary and metamorphic. A rock cycle defines how one rock form changes to another. For example, a sedimentary rock form is limestone that is composed only of the mineral calcite.</div>
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<a href="http://www.geologyin.com/2014/11/crystal-structure-and-crystal-system.html" target="_blank"><b>Crystal Structure and Crystal System</b></a></div>
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Main rocks on earth contain minerals like magnetite, quartz, feldspar, mica, epidote etc. But more than half of the mineral types classified in geological studies are considered rare. Igneous rocks are formed when molten lava solidifies after a volcanic eruption and is known to be rich in the mineral granite.</div>
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Sedimentary rocks are formed when deposition of organic matter, chemical precipitates etc takes place. These usually contain minerals like shale, siltstone, sandstone, etc. The metamorphic rocks are formed by the transformation of one rock type to another. No such process is applicable to minerals.</div>
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Rocks have great cultural, commercial and social value only because of the mineral present in them. Rocks are also used to establish dates of various civilizations that have existed on earth.<span style="font-family: "georgia" , "times new roman" , "times" , serif; font-size: 20px; margin: 0px; outline: none; padding: 0px;"><span style="margin: 0px; outline: none; padding: 0px;"></span></span></div>
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<span style="font-family: "georgia" , "times new roman" , serif;"><a href="http://www.geologyin.com/2014/12/how-to-classify-igneous-rocks-into.html" target="_blank"><b>How to classify Igneous rocks into (Ultramafic, Mafic, Intermediate and Felsic)?</b></a></span></div>
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<span style="font-family: Georgia, "Times New Roman", serif;"> Common Characteristics</span></h4>
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<span style="font-family: inherit;">Although there may be many differences between rocks and minerals, there are only a few similarities between them. Rocks as well as minerals are found in the Earth's crust (the outer layer of the Earth). Another similarity between the two is that rocks as well as minerals both have commercial value. Rocks are important for the minerals they contain while minerals are used widely in all areas of the manufacturing industry. Finally, both rocks and <a href="http://www.geologyin.com/2015/02/what-are-minerals-types-properties.html" target="_blank">minerals </a>serve as raw materials in the industrial process for manufacturing products used for everyday purposes.</span><span style="font-family: inherit; font-size: small;"> </span><br />
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<span style="font-family: Georgia, "Times New Roman", serif;"> Numerous Uses</span></h4>
There are several uses of rocks and <a href="http://www.geologyin.com/2015/02/what-are-minerals-types-properties.html" target="_blank">minerals </a>in the world today. Aluminum is used for making cans, containers and for appliances used in the home. Chromite is used for making chromed parts of automobiles. Ores of copper are used in making coins, jewelery, cooking utensils and wiring equipment used for electrical devices, televisions, computers, automobiles, etc. Halite, more commonly known as salt, is used in cooking and food preservation.<br />
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It is also used as a water softener and for de-icing on highways. Limestone is used as a component of cement which is used in the construction of homes, sidewalks, bridges and buildings. Fluorite find its uses in the production of hydrofluoric acid, but its main use is in toothpastes to help protect your teeth. Lead is used in making batteries and as a protective shield in the doctor's office from X-rays.<br />
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Rocks and minerals are fascinating topics of study for both scientists and students. While their own characteristics define them, they are sort of like distant cousins - having some similarities but keeping within their own immediate families.<br />
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<span style="font-family: "georgia" , "times new roman" , serif;"><b><a href="http://www.geologyin.com/" target="_blank">See also: </a></b></span></div>
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<span style="font-family: "georgia" , "times new roman" , serif;"><a href="http://www.geologyin.com/2014/12/10-most-rare-gemstones-in-world-rarer.html" target="_blank"><span style="color: black;"><b>10 Most Rare Gemstones in the World Rarer than a Diamond</b></span></a></span></div>
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<span style="font-family: "georgia" , "times new roman" , serif;"><a href="http://www.geologyin.com/2015/01/10-reasons-to-be-with-geologist.html" target="_blank"><b><span style="color: black;">10 Reasons to be with a Geologist</span></b></a></span></div>
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<span style="font-family: "georgia" , "times new roman" , serif;"><span class="" data-offset-key="cimor-0-0" data-reactid=".9t.1:4.0.$right.0.0.0.0.1.0.0.1.0.$cimor.0:$cimor-0-0"><a href="http://www.geologyin.com/2014/11/how-to-identify-minerals-in-10-steps.html" target="_blank"><b>How to Identify Minerals in 10 Steps (photos)</b></a></span></span></div>
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The Difference Between Rocks and Minerals

A mineral is a solid formation that occurs naturally in the earth while a rock is a solid combination of more than one mineral ...

Fire Agate

Minerals 4:04 PM

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<b>Fire Agate</b>, a variety of chalcedony, is a semi-precious natural gemstone found only in certain areas of northern Mexico and the southwestern United States. Approximately 24-36 million years ago these areas were subjected to massive volcanic activity during the Tertiary Period. The fire agates were formed during this period of volcanism when hot water, saturated with silica and iron oxide, repeatedly filled cracks and bubbles in the surrounding rock.<br />
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Fire Agate

Fire Agate , a variety of chalcedony, is a semi-precious natural gemstone found only in certain areas of northern Mexico and the southweste...

Petrophysics: The Study of Physical and Chemical Rock Properties

Geology, Oil, Petroleum 7:01 PM

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Petrophysics</span></h3>
<span style="font-family: Arial, Helvetica, sans-serif;">Is the study of physical and chemical rock properties and their interactions with fluids.A major application of petrophysics is in studying reservoirs for the hydrocarbon industry. Petrophysicists are employed to help reservoir engineers and geoscientists understand the rock properties of the reservoir, particularly how pores in the subsurface are interconnected, controlling the accumulation and migration of hydrocarbons. Some of the key properties studied in petrophysics are lithology, porosity, water saturation, permeability and density.</span><br>
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<span style="font-family: Arial, Helvetica, sans-serif;">A key aspect of petrophysics is measuring and evaluating these rock properties by acquiring well log measurements - in which a string of measurement tools are inserted in the borehole, core measurements - in which rock samples are retrieved from subsurface, and seismic measurements. These studies are then combined with geological and geophysical studies and reservoir engineering to give a complete picture of the reservoir.</span><br>
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<span style="font-family: Arial, Helvetica, sans-serif;">While most petrophysicists work in the hydrocarbon industry, some also work in the mining and water resource industries. The properties measured or computed fall into three broad categories: conventional petrophysical properties, rock mechanical properties, and ore quality.</span><br>
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<span style="font-family: Arial, Helvetica, sans-serif;">Petrophysical studies are used by petroleum engineering, geology, mineralogy, exploration geophysics and other related studies.</span></div>
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<span style="font-family: Arial, Helvetica, sans-serif;"><span class="mw-headline" id="Conventional_petrophysical_properties">Conventional petrophysical properties</span></span></h4>
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<span style="font-family: Arial, Helvetica, sans-serif;">Most petrophysicists are employed to compute what are commonly called conventional (or reservoir) petrophysical properties. These are:</span><br>
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<span style="font-family: Arial, Helvetica, sans-serif;"><b>Lithology: </b>A description of the rock's physical characteristics, such as grain size, composition and texture. By studying the lithology of local geological outcrops and core samples, geoscientists can use a combination of log measurements, such as natural gamma, neutron, density and resistivity, to determine the lithology down the well.</span><br>
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Petrophysics: The Study of Physical and Chemical Rock Properties

Petrophysics Is the study of physical and chemical rock properties and their interactions with fluids.A major application of petrophys...

Amazing Rosette Linarite

Minerals 3:28 AM

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<span style="font-family: "georgia" , "times new roman" , serif;"><span style="font-size: small;">large group of linarite crystals growing in "limonite" cavity.</span></span><br />
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<span style="font-family: "georgia" , "times new roman" , serif;"><span style="font-size: small;"><b>Linarite :</b> PbCu(SO4)(OH)2</span></span><br />
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<span style="font-family: "georgia" , "times new roman" , serif;"><span style="font-size: small;">Locality: Modrá štola, Zlaté Hory (Zuckmantel), Olomouc Region, Moravia (Mähren; Maehren), Czech Republic</span></span><br />
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<span style="font-family: "georgia" , "times new roman" , serif;"><span style="font-size: small;">Photo Copyright © Czechmin.cz</span></span></div>

Amazing Rosette Linarite

large group of linarite crystals growing in "limonite" cavity. Linarite : PbCu(SO4)(OH)2 Locality: Modrá štola, Zlaté H...

Normal Faults in Road Cut Near Shoshone - California

Structural Geology 5:04 PM

Normal Faults in Road Cut Near Shoshone - California

Hydraulic Fracturing of Oil & Gas Wells Drilled in Shale

Oil 4:12 PM

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What is Hydraulic Fracturing?</h3>
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Hydraulic fracturing is a procedure that can increase the flow of oil or gas from a well. It is done by pumping liquids down a well into subsurface rock units under pressures that are high enough to fracture the rock. The goal is to create a network of interconnected fractures that will serve as pore spaces for the movement of oil and natural gas to the well bore. <br>
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Hydraulic fracturing combined with horizontal drilling has turned previously unproductive organic-rich shales into the largest natural gas fields in the world. The Marcellus Shale, Utica Shale, Barnett Shale, Eagle Ford Shale and Bakken Formation are examples of previously unproductive rock units that have been converted into fantastic gas or oil fields by hydraulic fracturing. <br>
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Successful Use of Hydraulic Fracturing in Shale</h3>
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<span style="background-color: white; color: #555555; font-family: Arial, Helvetica, sans-serif; font-size: 13px;">In the early 1990s </span>Mitchel Energy<span style="background-color: white; color: #555555; font-family: Arial, Helvetica, sans-serif; font-size: 13px;"> began using hydraulic fracturing to stimulate the production of natural gas from wells drilled into the Barnett Shale of Texas. The </span>Barnett Shale<span style="background-color: white; color: #555555; font-family: Arial, Helvetica, sans-serif; font-size: 13px;">contained enormous amounts of natural gas, however, the Barnett rarely produced natural gas in commercial quantities. </span><br>
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<span style="background-color: white; color: #555555; font-family: Arial, Helvetica, sans-serif; font-size: 13px;">Mitchel Energy realized that gas in the Barnett Shale was trapped in tiny pore spaces that were not interconnected. The rock had pore space but lacked permeability. Wells drilled through the Barnett Shale would usually have a show of gas but not enough gas for commercial production. Mitchel Energy solved this problem by hydraulic fracturing the Barnett Shale to create a network of interconnected pore spaces that enabled a flow of natural gas to the well. </span><br>
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<span style="background-color: white; color: #555555; font-family: Arial, Helvetica, sans-serif; font-size: 13px;">Unfortunately many of the fractures produced by the hydraulic fracturing process snapped closed when the pumps were turned off. The Barnett Shale was so deeply buried that confining pressure closed the new fractures. This problem was solved by adding sand to the fracturing fluid. When the rock fractured, the rush of water into the newly-opened pore space would carry sand grains deep into the rock unit. When the water pressure was reduced the sand grains "propped" the fracture open and allowed a flow of natural gas through the fractures and into the well bore. Today there are a variety of natural and synthetic products that are sold under the name of "</span>frac sand<span style="background-color: white; color: #555555; font-family: Arial, Helvetica, sans-serif; font-size: 13px;">".</span><br>
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<span style="background-color: white; color: #555555; font-family: Arial, Helvetica, sans-serif; font-size: 13px;">Mitchel Energy further improved the yield of their wells by drilling them horizontally through the Barnett Shale. Vertical wells were started at the surface, steered to a horizontal orientation and driven through the Barnett Shale for thousands of feet. This multiplied the length of the pay zone in the well. If a rock unit was 100 feet thick, it would be have a pay zone of 100 feet in a vertical well. However, if the well was steered horizontal and stayed horizontal for 5000 feet through the target formation then the length of the pay zone was fifty times longer than the pay zone of a vertical well. </span><br>
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<span style="background-color: white; color: #555555; font-family: Arial, Helvetica, sans-serif; font-size: 13px;">Mitchel Energy used hydraulic fracturing and horizontal drilling to multiply the productivity of Barnett Shale wells. In fact, many of their highly successful wells would have been failures if they were vertical wells without hydraulic fracturing. </span></div>
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Hydraulic Fracturing in Other Shale Plays</h3>
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Hydraulic Fracturing of Oil & Gas Wells Drilled in Shale

What is Hydraulic Fracturing? Hydraulic fracturing is a procedure that can increase the flow of oil or gas from a well. It is done by p...

East Africa's Great Rift Valley: A Complex Rift System

Researches, Tectonic 5:23 PM

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 The East African Rift System</h3>
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The East African Rift System (EARS) is one the geologic wonders of the world, a place where the earth's tectonic forces are presently trying to create new plates by splitting apart old ones. In simple terms, a rift can be thought of as a fracture in the earth's surface that widens over time, or more technically, as an elongate basin bounded by opposed steeply dipping normal faults.<br />
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Geologists are still debating exactly how rifting comes about, but the process is so well displayed in East Africa (Ethiopia-Kenya-Uganda-Tanzania) that geologists have attached a name to the new plate-to-be; the Nubian Plate makes up most of Africa, while the smaller plate that is pulling away has been named the Somalian Plate (Figure 1).<br />
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These two plates are moving away form each other and also away from the Arabian plate to the north. The point where these three plates meet in the Afar region of Ethiopia forms what is called a triple-junction. However, all the rifting in East Africa is not confined to the Horn of Africa; there is a lot of rifting activity further south as well, extending into Kenya and Tanzania and Great Lakes region of Africa. The purpose of this paper is to discuss the general geology of these rifts are and highlight the geologic processes involved in their formation. <br />
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What is the East Africa Rift System?</span></h3>
The oldest and best defined rift occurs in the Afar region of Ethiopia and this rift is usually referred to as the Ethiopian Rift. Further to the South a series of rifts occur which include a Western branch, the "Lake Albert Rift" or "Albertine Rift" which contains the East African Great Lakes, and an Eastern branch that roughly bisects Kenya north-to-south on a line slightly west of Nairobi .<br />
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These two branches together have been termed the East African Rift (EAR), while parts of the Eastern branch have been variously termed the Kenya Rift or the Gregory Rift (after the geologist who first mapped it in the early 1900's). The two EAR branches are often grouped with the Ethiopian Rift to form the East Africa Rift System (EARS).<br />
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The complete rift system therefore extends 1000's of kilometers in Africa alone and several 1000 more if we include the Red Sea and Gulf of Aden as extensions. In addition there are several well-defined but definitely smaller structures, called grabens, that have rift-like character and are clearly associated geologically with the major rifts. Some of these have been given names reflecting this such as the Nyanza Rift in Western Kenya near Lake Victoria. Thus, what people might assume to be a single rift somewhere in East Africa is really a series of distinct rift basins which are all related and produce the distinctive geology and topography of East Africa. <br />
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How did these Rifts form?</span></h3>
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The exact mechanism of rift formation is an on-going debate among geologists and geophysicists. One popular model for the EARS assumes that elevated heat flow from the mantle (strictly the asthenosphere) is causing a pair of thermal "bulges" in central Kenya and the Afar region of north-central Ethiopia. These bulges can be easily seen as elevated highlands on any topographic map of the area (Figure 1). </div>
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As these bulges form, they stretch and fracture the outer brittle crust into a series of normal faults forming the classic horst and graben structure of rift valleys . Most current geological thinking holds that bulges are initiated by mantle plumes under the continent heating the overlying crust and causing it to expand and fracture. </div>
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Ideally the dominant fractures created occur in a pattern consisting of three fractures or fracture zones radiating from a point with an angular separation of 120 degrees. The point from which the three branches radiate is called a "triple junction" and is well illustrated in the Afar region of Ethiopia, where two branches are occupied by the Red Sea and Gulf of Aden, and the third rift branch runs to the south through Ethiopia.<br />
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The stretching process associated with rift formation is often preceded by huge volcanic eruptions which flow over large areas and are usually preserved/exposed on the flanks of the rift. These eruptions are considered by some geologists to be "flood basalts" - the lava is erupted along fractures (rather than at individual volcanoes) and runs over the land in sheets like water during a flood.<br />
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Such eruptions can cover massive areas of land and develop enormous thicknesses (the Deccan Traps of India and the Siberian Traps are examples). If the stretching of the crust continues, it forms a "stretched zone" of thinned crust consisting of a mix of basaltic and continental rocks which eventually drops below sea level, as has happened in the Red Sea and Gulf of Aden. Further stretching leads to the formation of oceanic crust and the birth of a new ocean basin. <br />
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East Africa's Great Rift Valley: A Complex Rift System

The East African Rift System The East African Rift System (EARS) is one the geologic wonders of the world, a place where the earth'...

Gemmy crystals of Native Sulfur atop Aragonite with Aragonite ps after Calcite!

Minerals 10:58 PM

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<a href="http://2.bp.blogspot.com/-Z3NhRi7fGzU/VHYwrc1-vdI/AAAAAAAACfs/yv56NUnslr8/s1600/10671431_785356238169795_4225140308108232013_n.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="416" src="http://2.bp.blogspot.com/-Z3NhRi7fGzU/VHYwrc1-vdI/AAAAAAAACfs/yv56NUnslr8/s1600/10671431_785356238169795_4225140308108232013_n.jpg" width="640" /></a></div>
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<span aria-live="polite" class="fbPhotosPhotoCaption" data-ft="{"tn":"K"}" id="fbPhotoSnowliftCaption" style="background-color: white; color: #141823; display: inline; font-family: 'lucida grande', tahoma, verdana, arial, sans-serif; font-size: 14px; line-height: 18px; outline: none; text-align: right; width: auto;" tabindex="0"><span class="hasCaption"><br /><span dir="ltr" style="font-family: Helvetica, Arial, 'lucida grande', tahoma, verdana, arial, sans-serif;">Gemmy crystals of Native Sulfur atop Aragonite with Aragonite ps after Calcite!<br />This is an impressive Sulfur specimen that is also a pseudomorph. The Sulfur crystals are scattered atop the Aragonite covered matrix, with the largest gemmy crystal measuring 3.2 cm in length. Just to the left of the largest Sulfur is a 4 cm Aragonite ps after a Calcite crystal. I suspect there may be as many as three more pseudos after Calcite atop the matrix.<br />From the long closed mines in the Agrigento Province, Sicily, Italy.<br />Measures 7 cm by 13.6 cm by 8.2 cm in total size.</span></span></span><span class="fbPhotoTagList" id="fbPhotoSnowliftTagList" style="background-color: white; color: #141823; display: inline; font-family: 'lucida grande', tahoma, verdana, arial, sans-serif; font-size: 14px; line-height: 18px; text-align: right;"><span class="fcg" style="color: #9197a3;">— </span></span></div>

Gemmy crystals of Native Sulfur atop Aragonite with Aragonite ps after Calcite!

Gemmy crystals of Native Sulfur atop Aragonite with Aragonite ps after Calcite! This is an impressive Sulfur specimen that is also a pse...

Clinoclase

Minerals 7:05 PM

Clinoclase

Clinoclase : Cu3(AsO4)(OH)3 Locality: Clara Mine, Rankach valley, Oberwolfach, Wolfach, Black Forest, Baden-Württemberg, Germany gr...

The River of Five Colors

tourism 2:12 PM

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Caño Cristales is a Colombian river located in the Serrania de la Macarena province of Meta. The river is commonly called "The River of Five Colors" or "The Liquid Rainbow", and is even referred to as the most beautiful river in the world due to its striking colors.<br>
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The bed of river in the end of July - November is colored in gaudy colors, including yellow, green, blue, black, and especially red, the last caused by the Macarenia clavigera (Podostemaceae) on the bottom of the river.<br>
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The River of Five Colors

Caño Cristales is a Colombian river located in the Serrania de la Macarena province of Meta. The river is commonly called "The River ...

Unique Annabergite from Greece

Minerals 2:27 PM

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<b><span style="font-family: "georgia" , "times new roman" , serif;"><span style="font-size: small;">Annabergite </span></span></b></div>
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Formula: Ni3(AsO4)2 · 8H2O<br />System: Monoclinic<br />Colour: Green, light grey to ...<br />Lustre: Sub-Adamantine, Sub-Vitreous, Pearly, Earthy<br /><br /><b><span style="font-family: Georgia,"Times New Roman",serif;">From</span></b>  Km-3 Mine, Lavrion (Laurion; Laurium), Lavrion District Mines, Lavrion District (Laurion; Laurium), Attikí Prefecture (Attica; Attika), Greece<br /><br /><span style="font-size: small;"><span style="font-family: inherit;"><span style="font-family: "georgia" , "times new roman" , serif;"><i><b>Photo Credit:  © Jean-Marc Johannet</b></i></span></span></span></div>

Unique Annabergite from Greece

Annabergite Formula: Ni3(AsO4)2 · 8H2O System: Monoclinic Colour: Green, light grey to ... Lustre: Sub-Adamantine, Sub-Vi...

Travertine Hot Springs at Pamukkale -Turkey

Geology, places to visit, tourism 3:23 AM

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Pamukkale's terraces natural site in Denizli Province in southwestern Turkey are made of travertine, a sedimentary rock deposited by water from the hot springs.</h4>
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In this area, there are 17 hot water springs in which the temperature ranges from 35 °C (95 °F) to 100 °C (212 °F). The water that emerges from the spring is transported 320 metres (1,050 ft) to the head of the travertine terraces and deposits calcium carbonate on a section 60 to 70 metres (200 to 230 ft) long covering an expanse of 24 metres (79 ft) to 30 metres (98 ft).<br>
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When the water, supersaturated with calcium carbonate, reaches the surface, carbon dioxide de-gasses from it, and calcium carbonate is deposited. The depositing continues until the carbon dioxide in the water balances the carbon dioxide in the air. Calcium carbonate is deposited by the water as a soft jelly, but this eventually hardens into travertine.<br>
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Travertine Hot Springs at Pamukkale -Turkey

Pamukkale's terraces natural site in Denizli Province in southwestern Turkey are made of travertine, a sedimentary rock deposited by w...

Amazing Carminite Crystals

Minerals 6:15 PM

Amazing Carminite Crystals

Volcano-powered electricity, the future of alternative energy.

Geothermal, volcano 1:45 PM

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We could exploit energy from deep down in the earth, as a report from a geothermal borehole suggests. The project developed under the name of Icelandic Deep Drilling Project (also known as IDDP), and the shafts have been drilled to almost five kilometers deep, with the purpose of harnessing the heat in the volcanic bedrock very deeply under the surface of Island.<br />
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The conclusions of this research are very important because of the estimations of the fossil fuels that will eventually run out. Even though there are ten to thirty years differences in predictions, depending on the source of the anticipations, coal gas and oil are about to end, point in which alternative energy sources will become a must for every country.<br />
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The main difference between the first and the second time when the magma was hit was the attempt to harness the energy of the magma. Of course, the success of the drilling procedure was as amazingly good news as it was pretty unpredictable, nonetheless a great thesis for future investigations.<br />
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The previous attempt was back in 2009, when the borehole in the northeast Iceland location Krafla was only 2,1 thousand meters high stroke a pocket of magma unexpectedly infringing into the upper crust from below, at an approximate temperature within the range of 900 – 1000°C.  After this incident, the purpose of the further investigations became highly increasing the energy resources of the country through the production of deep, supercritical geothermal fluids. A positive result of the investigation could lead to the possibility of increasing the power outputs of the geothermal wells that are suitable by magnitude, with no environmental foot prints increase rate.<br />
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Concerning the frequency of the phenomenon, ‘[d]rilling into magma is a very rare occurrence and this is only the second known instance anywhere in the world’, declared Wilfred Elders, co-author of the research papers and professor emeritus of geology at the University of California. He also declared that the IDDP and Iceland’s National Power Company conducting the Krafla geothermal power plant in the proximity are willing to make major investments for the research to continue until the conclusions will allow them to exploit the resources with appropriate new technologies.<br />
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Another source of great news for Iceland is the high concentration of volcanoes which, if found to be exploitable on a large scale, can be the source of enormous amounts of energy, that can be used to be transformed into electricity and further taken advantage of on industrial or even domestic level. Wilfred Elders also stated that ‘this could lead to a revolution in the energy efficiency of high-temperature geothermal projects in the future.’<br />
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The magma-heated steam is capable of producing 36 MW of electrical power, as the measurements have shown. In comparison with a standard 660 MW coal-fired power station this isn’t the most efficient source of energy, but it nonetheless registers way above the 1-3 MW of a standard wind turbine.</div>

Volcano-powered electricity, the future of alternative energy.

We could exploit energy from deep down in the earth, as a report from a geothermal borehole suggests. The project developed under the name...

Excellent Clinoclase Crystals

Minerals 8:21 PM

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<tr><td class="tr-caption" style="text-align: center;">Photo Copyright © Elmar Lackner </td></tr>
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<b>Clinoclase </b>: Cu<sub>3</sub>(AsO<sub>4</sub>)(OH)<sub>3</sub> <br />
Crystal System: Monoclinic<br />
Hardness: 2.5 - 3.0<br />
Tenacity: brittle<br />
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<b>Locality:</b> Tin stope, Majuba Hill Mine (Majuba Mine; Mylar Mine; Tin Mine; Nevada Bureau of Mines and Geology sample sites 2844 & 2846), Antelope District, Pershing Co., Nevada, USA<br />
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 Clinoclase is a <b>rare </b>secondary copper mineral and forms acicular crystals in the fractured weathered zone above copper sulfide deposits. It occurs in vitreous, translucent dark blue to dark greenish blue colored crystals and botryoidal masses. The crystal system is <b>monoclinic </b>2/m. It has a hardness of 2.5 - 3 and a relative density of 4.3. <b>Associated </b>minerals include malachite, olivenite, quartz, limonite, adamite, azurite, and brochantite among others. <br />
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<b>Abichite </b>is another name for clinoclase. </div>

Excellent Clinoclase Crystals

New Theory Suggests Gold Deposits Were Formed as a Result of Earthquakes

Geology, Gold 10:43 PM

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A new theory based on a simple but viable geologic model claims that over 80 percent of all commercial gold deposits were formed in a flash.<br /><br /><br />Gold seams are formed when mineral-rich waters flow through networks of cracks in rocks some 5-30 km deep. But the exact mechanism through which the gold is deposited is not really that well documented. According to this theory, local earthquakes brutally pull rocks apart, so fast that any fluids they contain are instantly vaporized, leaving behind the minerals they were carrying.<br /><br />Richard Henley of the Australian National University in Canberra and Dion Weatherley of the University of Queensland in Brisbane have studied earthquake dynamics, and found that quake-triggered pressure changes are much larger than was previously believed; earthquake-triggered pressure are traditionally considered to be part of the process, but their impact was considered to be quite small. According to Henley however, earthquakes can open cracks in the deep rocks at the speed of sound.<br /><br />As anybody who took a basic course in thermodynamics will tell you, the temperature at which water (or any fluid) boils is dependent on pressure. So when high pressures (remember, we’re a few km beneath the Earth’s surface) drop almost instantly under the influence of earthquakes, all the fluids are vaporized. As it evaporates, the minerals are deposited where they stood.<br /><br />“Large quantities of gold may be deposited in only a few hundred thousand years,” says Weatherley – a brief interval by geological standards. “Each event drops a little more gold,” adds Henley. “You can see it microscopically, tiny layer after tiny layer. It just builds up.”</div>

New Theory Suggests Gold Deposits Were Formed as a Result of Earthquakes

A new theory based on a simple but viable geologic model claims that over 80 percent of all commercial gold deposits were formed in a...

Fossilized Gastropod Replaced by Precious Emerald

Fossils 5:02 PM

Fossilized Gastropod Replaced by Precious Emerald

Formed from hydrothermal fluids in a shear zone interacting with the rock they passed through, the fossil in the host black shale was t...

Lake Mono’s Tufas

sedimentary, Structural Geology, tourism 10:35 PM

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Located in Owen’s Valley, California, Lake Mono is one of North America’s oldest lakes−over 1 million years old in fact, with a salinity of about 2.5 times than the ocean. Rivers and streams that flow down from the Sierra Nevada give the lake its unusually high salt and mineral content. The lake is also well known for being very alkaline with a pH of about 9.8, due to its high concentrations of carbonates.<br /><br />Seemingly out of a science fiction film, these formations, called tufas, rise up from the depths of the lake. Tufas are formed when calcium rich fresh water from springs interacts with the high alkaline lake water that is rich in carbonates. The ending results are these tufas which is actually your common limestone. The limestone builds from the ground up, creating these odd looking structures in the lake that have formed over millions of years.<br /><br />The formations used to be completely submerged beneath the lake until the 1940’s when major rivers were diverted from the lake to provide water for the city of Los Angeles. After the diversions, more water evaporated from the lake, which over time gave rise to the submerged tufas.<div>
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<span style="background-color: white; color: #333333; font-family: Helvetica, Arial, 'lucida grande', tahoma, verdana, arial, sans-serif; font-size: 12.727272033691406px; line-height: 15.12727165222168px; text-align: right;">Photo Credit:</span><br style="background-color: white; color: #333333; font-family: Helvetica, Arial, 'lucida grande', tahoma, verdana, arial, sans-serif; font-size: 12.727272033691406px; line-height: 15.12727165222168px; text-align: right;" /><span style="background-color: white; color: #333333; font-family: Helvetica, Arial, 'lucida grande', tahoma, verdana, arial, sans-serif; font-size: 12.727272033691406px; line-height: 15.12727165222168px; text-align: right;">Tim Malabuyo</span></div>
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Lake Mono’s Tufas

Located in Owen’s Valley, California, Lake Mono is one of North America’s oldest lakes−over 1 million years old in fact, with a salinity...

Largest Active Volcano on Earth shows Signs of Life

volcano 1:51 PM

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<span style="font-family: inherit;">Recent swarms of tiny earthquakes inside Hawaii’s Mauna Loa signal that the volcano may be coming back to life. But don’t cancel your vacation plans just yet.</span></div>
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<span style="font-family: inherit;">Mauna Loa is one of five volcanoes that form the Island of Hawaii in the U.S. It is the largest subaerial volcano in both mass and volume, and has historically been considered the largest volcano on Earth. It’s been probably erupting for about 700.000 years, though it emerged above sea level “only” 400.000 years ago. The last time it erupted was in 1984, but caused only minor damage.</span><br />
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<span style="font-family: inherit;">Now, researchers monitoring Mauna Loa reported four earthquake swarms, at shallow depths (above 15 kilometers), in the same places where they were reported in 1984. But it wasn’t just earthquakes that heralded the eruption in 1984 – so there’s no reason to fear yet.</span><br />
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<span style="font-family: inherit;">Before the eruption took place, geologists also reported swelling on the surface of the volcano and gas coming out of the volcano’s cracks. None of these has been reported now. No significant ground deformation, no gas emissions – so while there is some pressure building up in the magma chamber, there is no definite indication of an incoming eruption.</span><br />
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<span style="font-family: inherit;">Meanwhile, you can keep an eye on Mauna Loa using the <a href="http://www.esrl.noaa.gov/gmd/obop/mlo/livecam/livecam.html" rel="nofollow" style="border: 0px; color: #9bad34; margin: 0px; padding: 0px; text-decoration: none;" target="_blank">livecams set up by the USGS</a>.</span></div>
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Largest Active Volcano on Earth shows Signs of Life

Recent swarms of tiny earthquakes inside Hawaii’s Mauna Loa signal that the volcano may be coming back to life. But don’t cancel your vac...

Gemmy Apatite Crystals

Minerals 11:14 AM

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Cluster of lustrous, gemmy apatite crystals  from a classic locality. Specimen mounted on acrylic base. Color better in person. </div>
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Panasqueira Mines, Covilha, Castelo Branco District, Portugal</div>
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Gemmy Apatite Crystals

Credit: Spiriferminerals.com Cluster of lustrous, gemmy apatite crystals from a classic locality. Specimen mounted on acrylic ...

Quick Mineral Identification

Mineralogy 5:35 PM

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Quick identifying properties of several minerals.<br />
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Quick Mineral Identification

Quick identifying properties of several minerals.

Significance of fossils

Fossils 1:04 AM

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<strong style="background-color: white;">Explain the significance of fossils in sedimentary rocks.</strong><br />
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<b>fossil</b>—A remnant or trace of an organism of a some earlier geologic age, such as a skeleton or leaf imprint, embedded and preserved in the earth's crust. <br />
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<b>fossilization</b>—the processes that turn plant or animal remains to stone. <br />
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<b>Trace fossil</b>—a fossil impression of a footprint, trail, burrow, or other trace of an animal rather than of the animal itself.<br />
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<b>bioturbation</b>—the stirring or mixing of sediment or soil by organisms, especially by burrowing, boring, crawling, feeding or other traces left by biological activity.<br />
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Tuba City, Arizona</div>
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Significance of fossils

Explain the significance of fossils in sedimentary rocks. fossil —A remnant or trace of an organism of a some earlier geologic age, such...

Seismic Interpretation Basics

Geology, Petroleum, Seismic 2:57 PM

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<b style="margin: 0px; padding: 0px;"><span style="font-family: inherit;">Introduction:</span></b><br />
<span style="font-family: inherit;">Seismic interpretation, whether for hydrocarbon exploration or geotechnical studies, is the determination of the geological significance of seismic data. It is rare that the correctness (or incorrectness) of an interpretation can be ascertained, because the actual geology is rarely known in enough detail. Instead, the test of a good interpretation is consistency with all of the available data. In oil and gas exploration, emphasis is placed on finding an interpretation that is most favourable for hydrocarbon accumulation. As with many scientific investigations, interpretations are almost always non-unique.</span><br />
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<b style="margin: 0px; padding: 0px;"><span style="font-family: inherit;">Petroleum Geology - Basic Concepts:</span></b><br />
<ul style="margin: 0px 0px 0px 1.5em; padding: 0px;"><span style="font-family: inherit;">-Hydrocarbons are formed by burial and transformation of organic matter through chemical changes that are controlled by temperature and duration. Rocks that contain sufficient organic matter for the formation of hyrocarbons are called source rocks.<br style="margin: 0px; padding: 0px;" />-Hydrocarbons tend to be less dense than formation waters (brines) and therefore rise upwards under bouyancy forces.<br style="margin: 0px; padding: 0px;" />-The upward migration is stopped if there is a permeability barrier. The hydrocarbon trap must have closure.</span></ul>
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<b style="margin: 0px; padding: 0px;"><span style="font-family: inherit;">Key elements required for oil and gas accumulation:</span></b><br />
<ul style="margin: 0px 0px 0px 1.5em; padding: 0px;"><span style="font-family: inherit;">-A good source rock.<br style="margin: 0px; padding: 0px;" />-Sufficiently long burial of the source rock for the generation of hydrocarbons.<br style="margin: 0px; padding: 0px;" />-There must be a migration pathway.<br style="margin: 0px; padding: 0px;" />-There must be a hydrocarbon trap with a good reservoir rock (i.e., porous and permeable), a good seal (permeability barrier) and closure.<br style="margin: 0px; padding: 0px;" />-After accumulation of the hydrocarbons, nothing happens to degrade the reservoir.</span></ul>
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<b style="margin: 0px; padding: 0px;"><span style="font-family: inherit;">Seismic exploration is indirect!</span></b><br />
<span style="font-family: inherit;">Source rocks, degree of source rock maturity and migration pathways are generally not detectable using seismic data. It is sometimes (but not always) possible to distinguish hydrocarbons from formation fluids. Therefore, in hydrocarbon exploration programs the ultimate goal of seismic surveys is usually to map potential reservoirs for closure. Potential hydrocarbon traps are subsequently tested by drilling.</span><br />
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<b style="margin: 0px; padding: 0px;"><span style="font-family: inherit;">Examples of hydrocarbon traps:</span></b><br />
<ul style="margin: 0px 0px 0px 1.5em; padding: 0px;"><span style="font-family: inherit;">-Anticline<br style="margin: 0px; padding: 0px;" />-Termination of dipping layers at a fault<br style="margin: 0px; padding: 0px;" />-Termination of dipping layers at an unconformity<br style="margin: 0px; padding: 0px;" />-Facies change (permeable to impermeable)<br style="margin: 0px; padding: 0px;" />-Porous reef.<br style="margin: 0px; padding: 0px;" />-Bed termination at the side of a salt dome. Basic Seismic Interpretation Procedure</span></ul>
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<b style="margin: 0px; padding: 0px;"><span style="font-family: inherit;">Common Pitfalls of Seismic Interpretation:</span></b><br />
<ul style="margin: 0px 0px 0px 1.5em; padding: 0px;"><span style="font-family: inherit;">-Pull-up and pull-down caused by velocity distortions.<br style="margin: 0px; padding: 0px;" />-Multiple reverberations</span></ul>
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<b style="margin: 0px; padding: 0px;"><span style="font-family: inherit;">Synthetic Seismograms:</span></b><br />
<span style="font-family: inherit;">Synthetic seismograms are artificial seismic traces used to establish correlations between local stratigraphy and seismic reflections. To produce a synthetic seismogram, a sonic log is needed. Ideally, a density log should also be used, but these are not always available.</span><br />
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<b style="margin: 0px; padding: 0px;"><span style="font-family: inherit;">Procedure:</span></b><br />
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<ul style="margin: 0px 0px 0px 1.5em; padding: 0px;"><span style="font-family: inherit;">-Convert sonic transit times to velocity by taking the reciprocal (and applying scale factor as appropriate). Initially, the logs are sampled evenly in depth (e.g., 20 cm spacing between readings).<br style="margin: 0px; padding: 0px;" />-Use integrated velocity to convert log depths to two-way time.<br style="margin: 0px; padding: 0px;" />Sometimes velocity and density logs are resampled to be spaced equally in two-way time, instead of evenly spaced in depth.<br style="margin: 0px; padding: 0px;" />-Calculate the reflection coefficient for each sample point. The result is a reflection coefficient (RC) time series.<br style="margin: 0px; padding: 0px;" />-Convolve the RC time series with an assumed source wavelet.</span></ul>
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<b style="margin: 0px; padding: 0px;"><span style="font-family: inherit;">Notes:</span></b><br />
<span style="font-family: inherit;">Often, several wavelets and wavelet polarities are tested. Positive polarity usually refers to a wavelet for which the positive central peak coincides with a positive RC. Conversely, negative polarity means that a negative trough coincides with a positive RC after construction of the synthetic seismogram.</span><br />
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<b style="margin: 0px; padding: 0px;"><span style="font-family: inherit;">Vertical resolution of seismic data:</span></b><br />
<span style="font-family: inherit;">Vertical resolution can be thought of as the minimum resolvable bed thickness. There are two criteria that are used to define this limit:</span><br />
<ul style="margin: 0px 0px 0px 1.5em; padding: 0px;"><span style="font-family: inherit;">-The Rayleigh limit - bed thickness (h) is 1/4 of the seismic wavelength (or, two-way time thickness is 1/2 of the dominant seismic period). This is the tuning limit - i.e., maximum constructive interference between the top and bottom of the bed takes place for this value of bed thickness.<br style="margin: 0px; padding: 0px;" />-Widess limit - bed thickness is 1/8 of the seismic wavelength. This is the resolution limit. For example, if the velocity is 4000 m/s and the dominant frequency is 50 Hz, then the seismic wavelength is 80 m. Hence the resolution limit is 10 m - this is the thinnest resolvable bed thickness for these parameters.</span></ul>
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<b style="margin: 0px; padding: 0px;"><span style="font-family: inherit;">Horizontal resolution of seismic data</span></b><br />
<span style="font-family: inherit;">The horizontal resolution of unmigrated seismic data is given by the Fresnel zone, which has a width of:</span><br />
<span style="font-family: inherit;"><img alt="Image" src="http://upload.wikimedia.org/math/b/2/c/b2c48ee62c2ba4cfdd7b6e2f6501a0f4.png" style="border: none; margin: 0px; padding: 0px;" /></span><br />
<i style="margin: 0px; padding: 0px;"><span style="font-family: inherit;">Where:</span></i><br />
<ul style="margin: 0px 0px 0px 1.5em; padding: 0px;"><i style="margin: 0px; padding: 0px;"><span style="font-family: inherit;">Fn = The nth Fresnel Zone radius in metres<br style="margin: 0px; padding: 0px;" />d1 = The distance of P from one end in metres<br style="margin: 0px; padding: 0px;" />d2 = The distance of P from the other end in metres<br style="margin: 0px; padding: 0px;" />λ = The wavelength of the transmitted signal in metres</span></i></ul>
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<span style="font-family: inherit;">For example, for a velocity of 4000 m/s, a two-way time of 1.0 s and a frequency of 50 Hz, we have w = 141 m!</span><br />
<span style="font-family: inherit;"><br style="margin: 0px; padding: 0px;" /></span>
<span style="font-family: inherit;">In principle, the horizontal resolution of migrated seismic data is equal to the spatial Nyquist wavenumber (i.e., twice the CMP trace spacing - typically about 10 m). In practice, this horizontal resolution is never achieved, and a resolution of about 3-4 traces (typically 30-40 m) is more realistic.</span><br />
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<b style="margin: 0px; padding: 0px;"><span style="font-family: inherit;">Additional notes on salt domes:</span></b><br />
<ul style="margin: 0px 0px 0px 1.5em; padding: 0px;"><span style="font-family: inherit;">-Deeply buried salt is often less dense than the overlying strata, and is therefore subject to buoyancy forces.<br style="margin: 0px; padding: 0px;" />-Although in hand specimens halite is solid, over geologic time salt behaves like a viscous fluid.<br style="margin: 0px; padding: 0px;" />-Salt domes can be subdivided into swells (does not pierce overlying strata) or diapirs (overlying units are breached).<br style="margin: 0px; padding: 0px;" />-Stratigraphic thickening of adjacent beds can be used to deduce timing of diapirsm.</span><span style="font-family: inherit;"><ul style="margin: 0px 0px 0px 1.5em; padding: 0px;"><span style="font-family: inherit;"><br /></span></ul>
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<b>see also: </b><br />
<a href="http://www.geologyin.com/2014/12/hydrocarbon-traps.html" target="_blank"><b>Hydrocarbon traps</b></a><br />
<b><a href="http://www.geologyin.com/2014/08/petroleum-system.html" target="_blank">The Petroleum System</a></b><br />
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Seismic Interpretation Basics

Introduction: Seismic interpretation, whether for hydrocarbon exploration or geotechnical studies, is the determination of the geolo...

Geology In