Granite Porphyry Dikes Research Articles

ANALYSIS OF AGE INTERRELATIONS IN POST-ORE DIKES AND QUARTZ VEINS

A documentation of actual field observations relating to the structural and compositional aspects of post-ore dikes and quartz veins. Numerous examples are cited in an attempt to determine their genetic origins and consequent age relationships. Conclusions based on studies of atypical dikes and ore veins are presented. Kersantite dikes and geode fillings in Barun-Tsogto Mountain, Central Asia, and granite-porphyry dikes cut by quartz veins in Vostochnyy Yugodzyr Mountain illustrate the problems involved. L. A. Consiglio

Genetic considerations of magnetite and pyrrhotite in pyritic deposits, Yanahara District, southwestern Japan

The pyritic ores of the Yanahara district occur as irregular masses in felsic pyroclastic rocks (locally hornfels) of Permian age. Quartz porphyry and granite porphyry dikes cut both the ore deposits and country rock; zones of magnetite (with chlorite and plagioclase) are found adjacent to the dikes and country rock, and pyrrhotite (with small amounts of other sulfides, chlorite, and quartz) occurs between the magnetite zones and the pyritic ore, and also forms veinlike masses within the ore. Formation of the magnetite and pyrrhotite is attributed to processes of diffusion metasomatism as a result of interaction between the pyritic ore (and wall rocks) and ascending fluids associated with dike emplacement.

GEOLOGY OF THE CHLORIDE QUADRANGLE, ARIZONA

Research Article| April 01, 1953 GEOLOGY OF THE CHLORIDE QUADRANGLE, ARIZONA BLAKEMORE E THOMAS BLAKEMORE E THOMAS 12426½ VENTURA BOULEVARD, NORTH HOLLYWOOD, CALIFORNIA Search for other works by this author on: GSW Google Scholar GSA Bulletin (1953) 64 (4): 391–420. https://doi.org/10.1130/0016-7606(1953)64[391:GOTCQA]2.0.CO;2 Article history received: 17 Dec 1951 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation BLAKEMORE E THOMAS; GEOLOGY OF THE CHLORIDE QUADRANGLE, ARIZONA. GSA Bulletin 1953;; 64 (4): 391–420. doi: https://doi.org/10.1130/0016-7606(1953)64[391:GOTCQA]2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The Chloride quadrangle includes the southern two-thirds of the Cerbat Mountains, a range composed mostly of presumably Precambrian crystalline rocks. The oldest rocks are quartzite, mica schist, hornblende-diopside schist, and amphibolite. Younger and larger in amount are granite and granite gneiss. Gabbroic and dioritic gneiss, pegmatite, aplite, diabase, and mylonite also occur as part of the basement complex. The earliest rocks were strongly folded, but igneous intrusion and granitization have obliterated most of the folds. The rock types and the history of the basement complex compare closely with the Archean in the Grand Canyon.The area contains no Paleozoic rocks and probably no Mesozoic rocks. Intrusions of granite porphyry associated with mineralization are believed to be Tertiary. Dikes of granite porphyry, pegmatite, aplite, and lamprophyre are associated with these intrusions.Small areas of andesitic and rhyolitic extrusive rocks of Tertiary (?) age occur along the flanks of the range. Quaternary basalt caps these rocks in some places.Several periods of faulting and erosion are visible in the volcanic rocks. The latest faulting has produced the present mountains. The greatest displacement has been on the west side, and the Cerbat Range is an eastward-tilted fault block, modified in part into a horst. This mountain building seems to have occurred in late Tertiary and Quaternary time. Recent fault-block movement is suggested by the presence of canyon terraces and by the dissection of the pediment at the west base of the range. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Geology of the northern Quitman Mountains Trans-Pecos, Texas

The northern Quitman Mountains lie within the Sierra Madre Oriental structural province, where it projects northward from Mexico into Hudspeth County, Texas. The Permian Briggs formation with a maximum exposed thickness of about 200 feet unconformably underlies the Jurassic Malone formation, which, although absent in places, attains a maximum thickness of 100 feet. The Lower Cretaceous represented by 10,000 feet of sedimentary rocks, consists of the following formations, the maximum exposed thicknesses of which are given in parentheses: Torcer (300 feet), Yucca (5500 feet), Bluff (about 1800 feet), Cox (700 feet), Finlay (100 feet), Espy (1280 feet), and Etholen (500 feet). Unconsolidated basin deposits of late Tertiary and Quaternary age fill the valleys. The sedimentary rocks are intensely folded and faulted in the northern Quitman area, although no one fold can be followed very far. Three thrusts faults—the Devil Ridge, Red Hills, and Quitman—have a combined net slip of approximately 8 miles. Normal faults generally have a net slip less than 200 feet, though one exceeds 1000 feet. The main orogenic disturbance is probably late Cretaceous. Comagmatic and mildly alkalic volcanic and intrusive rocks are probably early Tertiary. Lavas and pyroclastic rocks, for which the name Square Peak volcanic series is here proposed, aggregate approximately 3500 feet and constitute a single unit in the center of the mountains. Flows range from rhyolite and trachyte to basalt; rhyolites are most abundant. Later basining, probably due to magmatic subsidence below the volcanics, has dropped the central portion of the volcanic rocks approximately 4500 feet. Centripetal dips of flows along the outer contacts are as high as 90°; average inward dips range from 20° to 40°. The Quitman pluton, a discontinuous elliptical ring of intrusives around the volcanic rocks, is interpreted as a ring-dike with an accessory stock at the northern end. Earliest intrusion in the area was a diorite; the main intrusion averages quartz monzonite. Plugs and dikes of aplite, granite porphyry, rhyolite porphyry, and quartz latite porphyry are youngest. Scattered mineral deposits are found in the irregular contact-metamorphic aureole around the pluton.

Morphology and its Development of the Kumano Coastal Mountain Region 2 (Tertiary History)

The Kumano Coastal Mountain is a range extending south-southwestwand from Ôdaigahara-san, one of the highest points in the Kii Peninsula. The Tertiary .history of this. mountain region is as follows: 1) Transgression of the Miyai Sea, Probably. at the beginning of the Oligocene, the Miyai Sea began to transgress slowly northwards over area of Mesozoic strata of complex structure. While the sea was encroaching upon certain parts of the land not so highly subdued, other regions situated far more inland were still undergoing reduction and were worn down nearly to a peneplane when the sea-reached there. 2) Post-Miyai Tectonic Movement. After the transgression of the Miyai Sea, the area was subjected to a great disturbance, such as severe block movements and foldings. 3) Post-Miyai Erosional Stage. After this period of disturbance an era of great. quiet prevailed, and for a long time the forces of destruction vigorously attacked the surface of the land and reduced it gradually to a low and rolling land. 4) Extrusion of the Kumano Acidic. Igneous Rocks, probably in the Miocene. A) The First Activity. At last the long period of quiet drew to a. close and lava flows of biotite felsoliparite and granophyric biotite liparite extruded through a. large fissure and covered a part of the Post-Miyai erosion surface. B) The Main Activity. Then persemic garnet-bearing biotite liparite intruded and partly extruded from a batholithic mass of acidic magma. During this time. the mass of magma was approaching the surface of the area and at last, extruded, shattering the roof rocks into pieces which were swallowed up in the molten magma, and it flowed over a rather wide area. This type of extrusion of biotite granite 'Porphyry and persemic liparite seems to be a kind of the “extrusion by de-roofing, ” as Prof. R. A. Daly calls it. Intrusion of dikes of granite porphyry and persemic liparite took place, accompanying the extrusion by de-roofing of the main mass, and also after it. 5) Post-Kumano Erosional Stage. The history of the district after the extrusion of the Kumano Acidic Igneous Rocks is as yet almost a blank, for throughout the whole area no rocks of this age have yet been identified. The land thus seems to have been undergoing erosion during late Neogene, ending in the formation of a. remarkable peneplane.