The low radioactivity of the formation would certainly be consistent with the origin of this schist as a product of regional metamorphism of basic igneous rocks. Some of the denser zones are matched with magnetite-rich basalts and sulfide-rich gabbro. Igneous rocks are divided into two groups, intrusive or extrusive, depending upon where the molten rock solidifies. Density of magmatic rocks correlates with mineral composition; density of (porous) sedimentary rocks depends on porosity, pore fluid, and matrix density. Basalt (extrusive rock) and granite (intrusive rock) are two of the most common igneous rock types on the Earth, and cover most of the igneous deposits on the planet.Usually, the rocks in deep ocean floors are known to be basaltic in nature, while the rocks in the continental mass are granitic in nature. Intrusive Igneous rocks will be Igneous Rocks DRAFT. siliceous metamorphic rocks generally have a lower bulk density than micaceous metamorphic rocks. The rocks that cause the geophysical anomalies are predominantly mafic volcanics interbedded with thousands of feet of clastic sediments deposited in response to subsidence of the rift. and a moderately high photoelectric factor (PeF), caused by iron in magnetite and ferromagnesian minerals. Igneous rocks can be easily identified with their texture, density, color, and mineral composition. Examples of extrusive igneous rocks include basalt, andesite, rhyolite, dacite, obsidian, pumice and scoria. So, for example, most of Vietnam's oil production comes from the fractured granite basement. crystal size. 4.2. Dipmeter Igneous and metamorphic rocks make up around 90 to 95% of the top 16 km of the crust of the earth by volume. Rock types include schist, gneiss, quartzite, arkosic quartzite, arkose, and undifferentiated metamorphic clastics (Merriam, 1963). The melt originates deep within the Earth near active plate boundaries or hot spots, then rises toward the surface. the silica and aluminosilicate minerals of acid igneous rocks results in moderate PeF values, magnetite and ferromagnesian minerals in basic igneous rocks causes high PeF values, typically low PeF values are logged in metamorphic rocks other than those with iron-bearing or other metallic minerals, low neutron porosity values in acid igneous rocks, fairly low neutron porosity values in basic igneous rocks, except for subaerially weathered basaltic lavas, low values in silica-rich metamorphics but increased values in micaceous rocks and very high values in chlorite schists, acid igneous rocks have a lower bulk density, basic igneous rocks have a much higher bulk density. porphyritic. The average density of basalt is 2.9 g/cm 3. These are the slowest cooling type of igneous rocks. First, a Precambrian granite. The melt originates deep within the Earth near active plate boundaries or hot spots, then rises toward the surface. Intrusive rocks also can be categorized consistent with the shape a… Density increases from bottom right to top left. Does the density differ in a hurricane? The great range in igneous and metamorphic rock composition means that individual formations should be considered on a … Evaporites The difference between granites and basalts is in silica content and their rates of cooling. Some neighboring wells produce oil directly from the fractured Precambian granite, as documented by Walters (1953) including a well approximately a mile to the east that had an initial production of 429 barrels of oil when it was drilled in 1938. Clastics and Coal This well was completed with oil production from the Granite wash that was commingled with production from the Pennsylvanian limestones. The upper section of the Precambrian in this well was identified from cuttings as biotite schist, with a sharp contact and lower section of layered gneisses of differing composition ranging between aplitic gneiss, gneiss, and amphibolitic gneiss. Igneous rock - Igneous rock - Mineralogical components: The major mineralogical components of igneous rocks can be divided into two groups: felsic (from feldspar and silica) and mafic (from magnesium and ferrous iron). Granite, for example, can have a quartz content anywhere between 20% and 60%. a magma chamber. Andesite and diorite are common rocks of the continental crust above subduction zones. Logging Terra Resources #1 Wangerin #1 is located in Smith County, Kansas and drilled through the Cambro-Ordovician Arbuckle Limestone into over a hundred feet of Precambrian metamorphics. Streak is the color of rock when it is crushed or powdered. Precambrian sediments and metasediments are found in a broad band across north-east Kansas. In looking at the logs, first notice the expanded scale with a range between -15 and 60 porosity units in order to accommodate the neutron porosity curve in the chlorite schist section. Below is a list of the different types of igneous rock texture. The contact between the Granite Wash and the granite can be seen in the marked increase in porosity to about 14%. Science. This is especially likely to happen if lava meets water. Click on any element for further details. 2. Resistivity Image Basalt is an iron-rich, very dark colored extrusive igneous rock. In other cases, different minerals may grow to distinctly different sizes. bulk density: the mean density of the considered rock volume (including pores, etc. We use cookies to help provide and enhance our service and tailor content and ads. Part of the logged section is shown next. The URL for this page is http://www.kgs.ku.edu/Publications/Bulletins/LA/09_igneous.html. Details on this well were reported by Newell et al. An extrusive igneous rock has a very low density. The bulk density of a rock is ρ B = W G /V B, where W G is the weight of grains (sedimentary rocks) or crystals (igneous and metamorphic rocks) and natural cements, if any, and V B is the total volume of the grains or crystals plus the void (pore) space.…. Now let us look at the logs of metamorphic rocks. The log below is from a well drilled in Russell County, where the Pennsylvanian LKC limestone-shale succession directly overlays a Granite Wash development from erosion of the Precambrian basement granite at the bottom of the well. Igneous rock composition chart: This chart shows that andesite is typically composed of plagioclase, amphiboles, and micas; sometimes with minor amounts of pyroxenes, quartz, or orthoclase. The felsic minerals include quartz, tridymite, cristobalite, feldspars (plagioclase and alkali feldspar), feldspathoids (nepheline and leucite), muscovite, and corundum. Density of igneous rocks depends almost exclusively on the mineralogical and chemical composition of these rocks, it increases with the increasing content of dark minerals . As magma cools the plutons form: What is a batholith The sedimentary rocks of the lower sequence are mostly tight arkoses and subarkoses, with an average porosity of 1.8%. The first log example is of a chlorite schist. siliceous metamorphic rocks generally have a lower bulk density than micaceous metamorphic rocks. Igneous rocks are divided into two groups, intrusive or extrusive, depending upon where the molten rock solidifies. It is probable that the original plan had been to finish drilling when the hole encountered granitic basement. The color of the igneous rock depends on the chemical composition of that rock. ; Mafic rocks are dominated by plagioclase and pyroxene (even if you can't see them with the naked eye) and smaller amounts of olivine. Due to the heterogeneity of rocks, it is necessary to distinguish between. Gamma Ray Igneous structures. are typically low in metamorphic rocks except those with significant potassium feldspar content. Igneous rocks (Granites). Texaco Poersch #1 was drilled in 1984 to a depth of 11300 feet, penetrating the igneous rocks and sediments within the Kansas leg of the MRS. As the deepest hole in Kansas, it was over half a mile deeper than any other borehole. In order to do this, 21 synthetic samples were defined, evenly distributed along the horizontal line in Fig. Occurrence of igneous rocks can be either intrusive (plutonic) or extrusive (volcanic). However, the density log will also be recorded as bulk density in gm/cc on any logging run. 2.Intermediate igneous rock: igneous rocks in which the silica content is moderate in quantity, along with feldspars. The density of dark color igneous rock is more than the light-colored igneous rock. 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