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Burlington Mylonite Zone
The Burlington mylonite zone is a 1.5 kilometer thick mylonite zone, resulting from the dynamic recrystallization and grain size reduction of rocks, running from Weston, Massachusetts to Lynnfield, Massachusetts and Danvers, Massachusetts. The deformation that formed the zone is believed to be related to the Bloody Bluff Fault. In 1976, R. O. Castle released information indicating that the Paleozoic Early Devonian Peabody Granite intruded the mylonite zone, giving a young age limit for the formation. The rocks within the Burlington mylonite zone are mainly fine-grained, laminated mylonites ranging to gneiss, with augen eye-shaped mineral grains. The zone also includes smaller includes of quartz schist and chlorite The chlorite ion, or chlorine dioxide anion, is the halite with the chemical formula of . A chlorite (compound) is a compound that contains this group, with chlorine in the oxidation state of +3. Chlorites are also known as salts of chlorous ac ... schist and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mylonite
Mylonite is a fine-grained, compact metamorphic rock produced by dynamic recrystallization of the constituent minerals resulting in a reduction of the grain size of the rock. Mylonites can have many different mineralogical compositions; it is a classification based on the textural appearance of the rock. Formation Mylonites are ductilely deformed rocks formed by the accumulation of large shear strain, in ductile fault zones. There are many different views on the formation of mylonites, but it is generally agreed that crystal-plastic deformation must have occurred, and that fracturing and cataclastic flow are secondary processes in the formation of mylonites. Mechanical abrasion of grains by milling does not occur, although this was originally thought to be the process that formed mylonites, which were named from the Greek μύλος ''mylos'', meaning mill. Mylonites form at depths of no less than 4 km. There are many different mechanisms that accommodate crystal-plastic def ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Weston, Massachusetts
Weston is a town in Middlesex County, Massachusetts, Middlesex County, Massachusetts, about 15 miles west of Boston. At the time of the 2020 United States Census, the population of Weston was 11,851. Weston was incorporated in 1713, and protection of the town's historic resources is driven by the Weston Historical Commission and Weston Historical Society. The town has one Local Historic District, 10 National Register Districts, 26 Historic Areas, and seven houses individually listed on the National Register of Historic Places. Weston's predominance as a residential community is reflected in its population density, which is among the lowest of Boston's suburbs near or within Massachusetts Route 128, Route 128. More than 2,000 acres, or 18 percent of the town's total acreage, have been preserved as parks, fields, wetlands, and forests, with 90 miles of trails for hiking, horseback riding, and cross-country skiing. Thirty-seven scenic roads, as defined by Massachusetts law, maintain ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lynnfield, Massachusetts
Lynnfield is a town in Essex County, Massachusetts, in the United States. At the 2020 census, the town population was 13,000. Lynnfield initially consisted of two distinct villages with a single governing body. Lynnfield Center comprises mostly an agricultural population, while South Lynnfield boasted a mixed culture. Together, the two towns evolved into one of the most prosperous suburbs in the North Shore region of Massachusetts. History The town of Lynnfield was first settled in 1638 and was made a district separate from Lynn in 1782. It was later officially incorporated in 1814. Historically, Lynnfield functioned as two separate villages connected by one governing body: in Lynnfield Center resided a mostly agricultural population, while South Lynnfield was a crossroad situated amongst neighboring larger towns. During this time, the town had two inns, a granite rock quarry, a small carbonated beverage bottler, and various eating institutions. The stagecoach line north fr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Danvers, Massachusetts
Danvers is a town in Essex County, Massachusetts, United States, located on the Danvers River near the northeastern coast of Massachusetts. The suburb is a fairly short ride from Boston and is also in close proximity to the renowned beaches of Gloucester and Revere. Originally known as Salem Village, the town is most widely known for its association with the 1692 Salem witch trials. It was also the site of Danvers State Hospital, one of the state's 19th-century psychiatric hospitals. Danvers is a local center of commerce, hosting many car dealerships and the Liberty Tree Mall. As of the 2020 United States Census, the town's population was 28,087. History Pre-Columbian era The area was long settled by indigenous cultures of Native Americans. In the historic period, the Massachusett, a tribe of the Pequot language family, dominated the area. The land that is now Danvers was once owned by the Naumkeag branch of the Massachusett tribe. Salem Village Around 1630, English colonists im ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bloody Bluff Fault
The Bloody Bluff fault is the boundary between the Milford-Dedham zone and the Nashoba zone in eastern Massachusetts. It runs between Westborough, Massachusetts and Lynnfield, Massachusetts. In the south, into Connecticut, the component Lake Char fault is poorly exposed. The Bloody Bluff fault zone is 3.2 kilometers wide in Framingham, Massachusetts and forms the five kilometer wide Burlington mylonite zone The Burlington mylonite zone is a 1.5 kilometer thick mylonite zone, resulting from the dynamic recrystallization and grain size reduction of rocks, running from Weston, Massachusetts to Lynnfield, Massachusetts and Danvers, Massachusetts. The de ... to the north. Rocks along the fault have experienced both ductile and brittle deformation. There is relatively little mylonite in the vicinity of Westborough. The fault is visible along I-495 just east of Westborough and further east, the Bloody Bluff-Lake Char fault splits into smaller branches. One of these faults, tentati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 ''zōḗ'' (), "life", meaning "ancient life" ). It is the longest of the Phanerozoic eras, lasting from , and is subdivided into six geologic periods (from oldest to youngest): # Cambrian # Ordovician # Silurian # Devonian # Carboniferous # Permian The Paleozoic comes after the Neoproterozoic Era of the Proterozoic Eon and is followed by the Mesozoic Era. The Paleozoic was a time of dramatic geological, climatic, and evolutionary change. The Cambrian witnessed the most rapid and widespread diversification of life in Earth's history, known as the Cambrian explosion, in which most modern phyla first appeared. Arthropods, molluscs, fish, amphibians, reptiles, and synapsids all evolved during the Paleozoic. Life began in the ocean ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Early Devonian
The Early Devonian is the first of three Epoch (geology), epochs comprising the Devonian period, corresponding to the Lower Devonian Series (stratigraphy), series. It lasted from and began with the Lochkovian Stage , which was followed by the Pragian from and then by the Emsian, which lasted until the Middle Devonian began, . During this time, the first Ammonoidea, ammonoids appeared, descending from Bactritida, bactritoid Nautiloidea, nautiloids. Ammonoids during this time period were simple and differed little from their nautiloid counterparts. These ammonoids belong to the order Agoniatitida, which in later epochs evolved to new ammonoid orders, for example Goniatite, Goniatitida and Clymeniida. This class of cephalopod molluscs would dominate the marine fauna until the beginning of the Mesozoic Era. References {{Geological history Early Devonian, Geological epochs Devonian geochronology, *01 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gneiss
Gneiss ( ) is a common and widely distributed type of metamorphic rock. It is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. Gneiss forms at higher temperatures and pressures than schist. Gneiss nearly always shows a banded texture characterized by alternating darker and lighter colored bands and without a distinct cleavage. Gneisses are common in the ancient crust of continental shields. Some of the oldest rocks on Earth are gneisses, such as the Acasta Gneiss. Description Orthogneiss from the Czech Republic In traditional English and North American usage, a gneiss is a coarse-grained metamorphic rock showing compositional banding (gneissic banding) but poorly developed schistosity and indistinct cleavage. In other words, it is a metamorphic rock composed of mineral grains easily seen with the unaided eye, which form obvious compositional layers, but which has only a weak tendency to fracture ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Augen
Augen (from German "eyes") are large, lenticular eye-shaped mineral grains or mineral aggregates visible in some foliated metamorphic rocks. In cross section they have the shape of an eye. Feldspar, quartz, and garnet are common minerals which form augen. Augen form in rocks which have undergone metamorphism and shearing. The core of the augen is a porphyroblast or porphyroclast of a hard, resilient mineral such as garnet. The augen grows by crystallisation of a ''mantle'' of new mineral around the porphyroblast. The mantle is formed contiguous with the foliation which is imparted upon the rock, and forms a blanket which tapers off from either side of the porphyroblast within the strain shadows. During shearing, the porphyroblast may rotate, to form a characteristic augen texture of asymmetric shearing. In this case, the position of the tails is unequal across the foliation, with some augen showing clear drag folding of the mantle into the strain shadow. This derives a form ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quartz
Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical formula of SiO2. Quartz is the second most abundant mineral in Earth's continental crust, behind feldspar. Quartz exists in two forms, the normal α-quartz and the high-temperature β-quartz, both of which are chiral. The transformation from α-quartz to β-quartz takes place abruptly at . Since the transformation is accompanied by a significant change in volume, it can easily induce microfracturing of ceramics or rocks passing through this temperature threshold. There are many different varieties of quartz, several of which are classified as gemstones. Since antiquity, varieties of quartz have been the most commonly used minerals in the making of jewelry and hardstone carvings, especially in Eurasia. Quartz is the mineral defining the val ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Schist
Schist ( ) is a medium-grained metamorphic rock showing pronounced schistosity. This means that the rock is composed of mineral grains easily seen with a low-power hand lens, oriented in such a way that the rock is easily split into thin flakes or plates. This texture (geology), texture reflects a high content of platy minerals, such as micas, talc, chlorite group, chlorite, or graphite. These are often interleaved with more granular minerals, such as feldspar or quartz. Schist typically forms during regional metamorphism accompanying the process of mountain building (orogeny) and usually reflects a medium Metamorphism#Metamorphic grades, grade of metamorphism. Schist can form from many different kinds of rocks, including sedimentary rocks such as mudstones and igneous rocks such as tuffs. Schist metamorphosed from mudstone is particularly common and is often very rich in mica (a ''mica schist''). Where the type of the original rock (the protolith) is discernible, the schist is us ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chlorite
The chlorite ion, or chlorine dioxide anion, is the halite with the chemical formula of . A chlorite (compound) is a compound that contains this group, with chlorine in the oxidation state of +3. Chlorites are also known as salts of chlorous acid. Compounds The free acid, chlorous acid HClO2, is the least stable oxoacid of chlorine and has only been observed as an aqueous solution at low concentrations. Since it cannot be concentrated, it is not a commercial product. The alkali metal and alkaline earth metal compounds are all colorless or pale yellow, with sodium chlorite (NaClO2) being the only commercially important chlorite. Heavy metal chlorites (Ag+, Hg+, Tl+, Pb2+, and also Cu2+ and ) are unstable and decompose explosively with heat or shock. Sodium chlorite is derived indirectly from sodium chlorate, NaClO3. First, the explosively unstable gas chlorine dioxide, ClO2 is produced by reducing sodium chlorate with a suitable reducing agent such as methanol, hydrogen perox ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
