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Topic: Epidosite


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In the News (Wed 15 Feb 12)

  
  Epidosite - LoveToKnow 1911
EPIDOSITE, in petrology, a typical member of a family of metamorphic rocks composed mainly of epidote and quartz.
The epidosites derived from limestones may contain a great variety of minerals such as calcite, augite, garnet, scapolite, andc., but their source may usually be inferred from !their close association with calc-silicate rocks in the field.
The third group of epidosites may form bands, veins, or irregular streaks and nodules in masses of epidiorite and hornblende-schist.
www.1911encyclopedia.org /Epidosite   (261 words)

  
 Epidosite - Wikipedia, the free encyclopedia
Epidosite is a highly altered epidote and quartz bearing rock.
It is the result of extreme hydrothermal fluid alteration of basalt that occurs below the fl smokers within mid-oceanic ridge spreading centers.
Epidosites represent the zone of intense metal leaching below and lateral to the fl smoker environment which is the result of convection of ocean water through the fractured basalts of the ridge flanks.
en.wikipedia.org /wiki/Epidosite   (124 words)

  
 Epidote - LoveToKnow Watches
It occurs in crystalline limestones and schistose rocks of metamorphic origin; and is also a product of weathering of various minerals (felspars, micas, pyroxenes, amphiboles, garnets, andc.) composing igneous rocks.
A rock composed of quartz and epidote is known as epidosite.
The perfectly transparent, dark green crystals from the Knappenwand and from Brazil have occasionally been cut as gem-stones.
www.1911encyclopedia.org /Epidote   (585 words)

  
 [No title]
In contrast, the presence of epidosite (epidote-quartz rock) lenses and layers in Catoctin Formation metabasalt indicates that it was locally subjected to chemical migration during metamorphism (Reed and Morgan, 1971).
Epidosite, a fine-grained, massive, yellowish-green rock consisting of epidote and quartz occurs as discontinuous layers or boudins as much as a few feet in length.
Lensoid aprons of subangular clasts of quartzite, phyllite, greenstone, epidosite, and vein quartz cover the strata of the western part of the Culpeper basin and were derived from the escarpment of the east limb of the Blue Ridge anticlinorium; these deposits can be seen along Route 15 north of Lucketts (Burton and others, 1994a).
geology.er.usgs.gov /eespteam/GISLab/Search/Virginia/loudoun/LOUDOUN.TXT   (14457 words)

  
 [No title]
Note, comments may take some time to be approved.
The epidosites derived from limestones may contain a great variety of minerals such as calcite, augite, garnet, scapolite, andc., but their source may usually be inferred from their close association with talc-silicate rocks in the field.
In microscopic section they are often merely a granular mosaic of quartz and epidote with some iron oxides and chlorite, but in other cases they retain much of the structure of the originar rock though there has been a complete replacement of the former minerals by new ones.
encyclopedia.jrank.org /correction/edit?locale=en&content_id=23241   (282 words)

  
 USGS B 2123 -- Metamorphism
Albite, chlorite, and magnetite are found in all of these rocks; actinolite and epidote are abundant in metabasalt, and sericite is abundant in the aluminosilicate-rich rocks.
Epidosite is most common in metabasalt flows (Reed and Morgan, 1971) but is also found in metadiabase dikes as a result of circulating fluids (Espenshade, 1986).
White quartz veins are common in all units.
pubs.usgs.gov /bul/b2123/meta.html   (307 words)

  
 EarthRef.org Reference Database (ERR) -- Nehlig et al. 1994   (Site not responding. Last check: 2007-10-25)
Their vertical distribution is also anisotropic: epidosites occur mainly in the basal sheeted-dike complex, and mineralized spilites are usually limited to its top and to the transition zone with the volcanic extrusives.
The sheeted-dike complex underlying these deposits is characterized by a sharp increase in the volume of epidosite and mineralized spilite.
The common occurrence of epidosite bands devoid of veins, and the absence of major fracturing or listric faulting, indicates that formation of epidosite does not first require tectonic extension.
earthref.org /cgi-bin/err.cgi?n=40277   (301 words)

  
 Ophiolites - Biocrawler   (Site not responding. Last check: 2007-10-25)
The circulation of hydrothermal fluid through young oceanic crust causes serpentinization alteration of the minerals observed: chlorite and serpentine, for example, in the sheeted dikes.
Often, ore bodies such as iron-rich sulfide deposits are found above highly altered epidosites (epidote-quartz rocks) that are evidence of (the now relict) fl smokers which continue to operate within the seafloor spreading centers of ocean ridges today.
Thus there is reason to believe that ophiolites are indeed oceanic mantle and crust; however, certain problems arise when looking closer.
www.biocrawler.com /encyclopedia/Ophiolites   (597 words)

  
 EVALUATION OF HYDROTHERMAL ALTERATION MINERAL ASSEMBLAGES AND THEIR RELATIONSHIP TO VMS-STYLE MINERALIZATION IN THE ...   (Site not responding. Last check: 2007-10-25)
Mass balance analysis indicates that the epidosite zones are enriched in CaO, and depleted in Na2O, K2O, MnO, Fe2O3, FeO, Zn, and Cu relative to the least altered diabase.
These epidosite zones represent local high water:rock ratio alteration within lower semi-conformable alteration zones associated with base metal leaching.
Crosscutting SQ alteration zones occur in northeastern trending zones located in the central and east-central parts of the prospect.
gsa.confex.com /gsa/2001AM/finalprogram/abstract_27423.htm   (416 words)

  
 Modal Classification
Katchan (1982) and Duncan (1972) suggest that most of the skarn at Ok Tedi is endoskarn and thus formed from intrusive host rocks.
I excluded samples of massive garnetite, epidosite, and endoskarn from my detailed petrographic studies.
Epidote is found as partial pseudomorphic replacements of plagioclase feldspar, as an infilling mineral in veinlets (Figure 43A and B), and as disseminated anhedral to subhedral crystals that may have originated by the replacement of earlier-formed minerals or by the filling of void spaces (Figure 43C and D).
www.fortunecity.co.uk /safaripark/lamprey/108/pnlith3.htm   (4756 words)

  
 GeologyRocks :: Tutorials :: The Geology of Cyprus   (Site not responding. Last check: 2007-10-25)
This fact, combined with the fact that no consistent relationships are evident between age and composition, suggests that within each individual spreading axis, dykes were intruded at a number of spreading centres, possibly overlapping (Robinson and Malpas, 1990).
The dykes also have been metamorphosed, ranging in grade from zeolite to greenschist facies, with 'epidosite' (epidote-quartz-sphene) zones marking the base of hydrothermal recharge systems (Richardson, Cann et al., 1987).
Above the Sheeted dykes complex is the Basal Group, sandwiched between the dykes and the overlying pillow lavas.
www.geologyrocks.co.uk /tutprint.php?id=22   (4606 words)

  
 4 vanderMolen   (Site not responding. Last check: 2007-10-25)
This chlorite schist is made up of the minerals quartz and chlorite.
Epidosite is composed mainly of the minerals epidote and quartz.
It is usually pale or greenish yellow, and hard and somewhat brittle.
hrsbstaff.ednet.ns.ca /dvm/geology/metamorphic.htm   (382 words)

  
 TEAL Exploration and Mining Incorporated   (Site not responding. Last check: 2007-10-25)
Along the southern edge of the Northern Platform the Askevold Formation is developed at the top of the Nosib Group.
This formation consists of phyllites, intermediate agglomerate, tuff and epidosite (possibly edipotised lava or andesite).
The "platform facies" consist of dolomite and limestone with subordinate shale, arkose and greywacke (Abenab Subgroup); mixtite, with a variety of other rock types, such as quartz-mica schist, quartzite, conglomerate, dolomite, iron-formation and calc-silicate rocks (Chuos Formation); dolomite and limestone, intraformation breccias or conglomerates (remainder of Tsumeb Subgroup).
www.tealmining.com /properties/namibia_gold_exploration.asp   (4674 words)

  
 Morning Star Mine (Morning Star prospects; Morning Star pegmatites), San Domingo Wash, White Picacho District, Maricopa ...   (Site not responding. Last check: 2007-10-25)
The country rock in this general area is thinly foliated to slabby amphibole schist, quartz-biotite schist, and quartz-biotite-muscovite schist, most of which is medium dark gray in color.
These rock types are intimately interlayered, and locally contain lenses of amphibolite and epidosite.
Most appear to be of volcanic origin, and several thick, tabular masses of agglomerate and breccia are clearly recognizable.
www.mindat.org /loc-52207.html   (435 words)

  
 Sr isotope geochemistry and hydrothermal alteration of the Oman ophiolite
Sr 0.70584, and 76% degree of alteration; (3) basalts and sheeted dike diabase and prehnite-actinolite facies, moderate alteration temperature, average
Sr 0.70519, and 85% degree of alteration; (4) dike diabase, plagiogranite, metagabbro and epidosite and prehnite-free greenschist facies, high alteration temperature, average
Sr 0.70514, and 65% degree of alteration; and (5) noncumulate and cumulate gabbro and amphibolite facies, very high alteration temperature, average
www.agu.org /pubs/crossref/2001/2000JB900456.shtml   (369 words)

  
 Geology Rocks :: Tutorials   (Site not responding. Last check: 2007-10-25)
Within the Sheeted Dyke Complex, zones of epidote-quartz-magnetite rocks up to 900m wide are found, having sharp contrasts with the background ‘normal’ diabase dykes.
These ‘epidosite’ zones are thought to form the hydrothermal reaction zones of the major hydrothermal systems that produced the massive sulphide and stockwork deposits of the Troodos ophiolite.
These areas have been stripped of copper, zinc and manganese, as well as removing some sodium, and several are seen to lie along strike from major mining districts in Cyprus.
www.geologyrocks.co.uk /tut.php?id=20   (2276 words)

  
 pmag keck student studies
Girby, C. (Amherst College), 1996, Structural interpretation of the gabbro in the Solea graben, Troodos ophiolite, Cyprus: in The Ninth Keck Geology Consortium Research Symposium, p.
Johnson, C. (Carleton College), 1996, Structural controls on epidosite formation and timing of hydrothermal alteration, in The Ninth Keck Geology Consortium Research Symposium, p.
Huskey, A. (SE Missouri St. Univ), 1996, Using paleomagnetism to determine magma flow direction within the sheeted dike complex of the Troodos ophiolite, in The Ninth Keck Geology Consortium Research Symposium, p.
www.wooster.edu /geology/pmagpages/keckstudies.html   (360 words)

  
 GemRocks: Unakite
And, I suspect that at least the one from Mexico might resemble stones fashioned from epidote-rich portions of unakite (e.g., the faceted one in the upper right of Figure B).
Indeed, one wonders if either, or both, of these rocks is spatially associated with unakite: Epidosite and unakite have been found so related near Fisher's Gap, in the Blue Ridge Povince of Madison County, Virginia (Phalen, 1903).
A lesson for collectors: I still bear a scar from a deep cut and loss of much blood suffered from a small flying disc broken from a student's apparently improperly tempered hammer while she was trying to get a good sample of unakite from the Airpoint mass southwest of Roanoke, Virginia.
www.cst.cmich.edu /users/dietr1rv/unakite.htm   (1094 words)

  
 Technical Program
Hydrothermally-derived rock types consist of a variety of aluminous gneiss, aluminous veins and nodules, and meta-exhalite.
The latter form an atypical package of finely-laminated garnetite, garnetiferous hornblendite, Mn or Ba-rich coticule, garnet or clinopyroxene amphibolite to which are associated some epidosite, biotitite, albitite, calc-silicate, marble and anorthite-rich units.
Metamorphic assemblages, mode and mineral colour vary according to whole-rock composition.
www.cim.org /meetings/Abstract.cfm?PaperNum=807&ShowID=33   (416 words)

  
 Rock and Mineral Specimen Collections from Rockman
Metamorphic Rock Collection - Fifteen 1.5" specimens (biotite gneiss, graphite schist, staurolite mica schist, garnet mica schist, chlorite schist, slate, phyllite, soapstone, quartzite, serpentine, epidosite, marble, serpentine marble, amphibolite, hornfels) in a display box.
We have had a number of inquiries about collections of larger specimens so we are now offering this metamorphic rock collection which includes 12 of our 3 inch plus lab size specimens.
The 12 are biotite gneiss, graphite schist, staurolite mica schist, garnet mica schist, chlorite schist, slate, soapstone, quartzite, epidosite, marble, amphibolite and hornfels.
www.rocksandminerals.com /boxed/boxed.htm   (1833 words)

  
 [No title]
Jeff Gee has recently concentrated on applications of paleomagnetic and magnetic anomaly data to understanding crustal accretionary processes at mid-ocean ridges.
These studies include investigating the role of geochemistry and alteration in controlling magnetization variations, examining the uplift and alteration history of lower crustal gabbros and serpentinized peridotites exposed at the Mid-Atlantic Ridge, and a variety of projects in the Troodos ophiolite (e.g., magma flow in dikes, timing of epidosite alteration).
Steve Cande, Jeff Gee, and Bob Parker are actively investigating (through near bottom magnetic data and magnetostratigraphic studies) whether lineated marine magnetic anomalies may preserve a record of geomagnetic intensity variations as well as providing the template for the polarity timescale.
mahi.ucsd.edu /cathy/geomag.html   (1602 words)

  
 Site Summary: Sites 1110, 1111, 1112 and 1113   (Site not responding. Last check: 2007-10-25)
Another thick pile of talus deposits in Pleistocene (<1.75 Ma) sediments including silty clay with occasional ash required two RCB holes to reach 165 mbsf.
The recovery consisted of pebbles only, mostly of metadiabase and epidosite, but also minor andesite, micro-granite, micaschist and sediments (sandstone and siltstone).
After offsetting 1.3 km south, we attempted a "bare rock" spud at the base of slope of Moresby Seamount where the fault crops out (Site 1113), but there was enough talus to make the hole unstable and repeatedly re-fill, and it was abandoned at 25 mbsf in micaschist and epidosite pebbles and cobbles.
www.odp.usyd.edu.au /news/weekly/1113.html   (616 words)

  
 t32f in fm97
------------------------------ AN: T32F-05 LO: MC 310 HR: 1430h DA: Wednesday TI: Role of Dyke Intrusion in Black Smoker Hydrothermal Systems: Evidence From the Epidosite Zones of the Troodos Ophiolite, Cyprus AU: *G Penwright, J Cann MN: Fall Meeting 1997
Within these epidosite zones, individual dykes are altered to assemblages of greenschist facies minerals occuring as stripes of more or less intensely altered rock within the dyke.
The stripes run parallel to the margins of curving dykes, and are abruptly interrupted where dykes are cut by others, suggesting that the stripes were formed soon after dyke intrusion.
www.agu.org /cgi-bin/SFgate/SFgate?&listenv=table&multiple=1&range=1&directget=1&application=fm97&database=/data/epubs/wais/indexes/fm97/fm97&maxhits=200&="T32F"   (3012 words)

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