Felsite Porphyry Research Articles

Geochemistry, geochronology, and zircon Hf isotopic compositions of felsite porphyry in Xiangshan uranium orefield and its geological implication

Recently, a new kind of volcanic rock, felsite porphyry, has been revealed by drilling in Xiangshan area, Jiangxi Province, China. To better understand petrogenesis and magmatic evolution sequence of the Xiangshan volcanic-intrusive complex, we studied systematic petrology, geochemistry, LA-ICP-MS zircon U–Pb dating, and Hf isotope results of the felsite porphyry. Results show that the felsite porphyry has similar geochemical characteristics to the porphyroclastic rhyolite, which is the predominant lithology of Xiangshan uranium orefield. Felsite porphyry and porphyroclastic rhyolite have high SiO2, Al2O3, and K2O contents, low Na2O, and MgO contents, and slightly negative Eu anomalies. Moreover, these rocks are relatively depleted in large ion lithophile elements (K, Ba, and Sr) and are enriched in high field strength elements (Th, Zr, and Hf). LA-ICP-MS zircon U–Pb dating of the felsite porphyry yielded a crystallization age of 132.2 ± 0.9 Ma, which is coeval to that of the porphyroclastic rhyolite. These ages signified that Xiangshan volcanic-intrusive complex formed in the Early Cretaceous, during which the entire South China was in the back-arc extension tectonic setting related to the subduction of the Pacific Plate under the Euroasian Plate. In-situ zircon Hf isotope data on a felsite porphyry sample show eHf(t) values from − 8.82 to − 5.11, while the Hf isotope two-stage model age (TDM2-Hf) ranges from 1513 to 1747 Ma. Combined with petrological, mineralogical, geochemistry, and geochronology results of the felsite porphyry, it is concluded that the felsite porphyry in Xiangshan might be originated from the partial melting of the Mesoproterozoic ancient metamorphic rocks, with possible input of small amounts of mantle materials.

Geological Features of Iron Formations and Associate Rock in Bulunkuole Group, West Kunlun, Xinjiang, China

West Kunlun is located at northwest part of the Tibetan plateau, and it’s divided into North Kunlun terrane, South Kunlun terrane and Tianshuihai terrane. Bulunkuole Group is located in Tianshuihai terrane, and Taaxi, Yelike, Laobing, Zankan, Mokaer and Jiertiekegou iron deposit was found in this terrane. Those iron deposits are set to the important iron ore mineralization belt of Xinjiang and even China. By investigation the geological features, ore distributions, and mineralization characters; and analyze the electron microprobe of magnetite and pyrite, stable isotope of pyrite, magnetite and anhydrite to discussion the tectonic setting and its genesis analysis iron ore deposit in Blunkuole Group, and establish the metallogenic model in this area. By contrastive analyzing of Taaxi, Yelike Zankan-Mokar iron ore deposits in Bulunkuole Group, it was found that all the iron ore deposit share the similar sedimentary environment. Those deposits have 3 ∼ 4 ore bodies, each get a meter to dozens of meters in width, extend to thousands of meters. The wall rocks are biotite quartz schist and plagioclase amphibole schist, and the two rocks interbed usually. It should be distinguish in the stratigraphic correlation of Bulunkuole Group for the influenced by the magma intrusion, such as granite and felsite porphyry.

Zircon U–Pb ages and Hf isotope of the granitoids from the Xingwen porphyry molybdenum deposit in the Xiaoxing'an Range – Zhangguangcai Range metallogenic belt, NE China

The newly discovered Xingwen porphyry Mo deposit is located in the most southern segment of the Xiaoxing'an Range–Zhangguangcai Range metallogenic belt (XZMB), NE China. The Mo deposit occurs with a granitic complex consisting of monzogranite, porphyritic granite and felsite porphyry. The Zircon U–Pb ages of monzogranite, porphyritic granite and felsite porphyry are 170.3 ± 2.1, 168.5 ± 2.5, and 166.7 ± 1.6 Ma, respectively. The inherited zircons from the monzogranite and porphyritic granite yield U–Pb ages of 239.8 ± 5.8 and 249.4 ± 6.2 Ma, respectively. These ages reveal that the Mo mineralization in the most southern segment of the XZMB took place in the Middle Jurassic, and is consistent with the epoch of the largest Daheishan Mo district in the XZMB. In contrast, Triassic ages of the inherited zircons are consistent with the ages of the Triassic magmatic activities along the E–W trending tectono‐magmatic belt in the northern margin of the North China Craton. The εHf(t) of the monzogranite, porphyritic granite and felsite porphyry change from −17.1 to +6.7 , −16.9 to +2.9, −5.94 to −0.90, respectively. The Hf isotopic compositions indicate that old crustal source, juvenile crustal source or depleted mantle contributed to their origin. When compared with the granite in Daheishan Mo district in XZMB, the εHf(t) probably indicates that the granitic complex in the margin of the Central Asia Orogenic Belt may have more old crustal materials than the granitic complex in the inner region of the Central Asia Orogenic Belt. Copyright © 2017 John Wiley & Sons, Ltd.

The Late Neoproterozoic rift-related metarhyolite–basalt association of the Glushikha trough (Yenisei Ridge): petrogeochemical composition, age, and formation conditions

New data are presented on the petrogeochemical composition, age, and formation conditions of the Late Neoproterozoic metarhyolite–basalt association of the Glushikha trough (Yenisei Ridge). The association is localized within the subaerial and shallow-water terrigenous-carbonate sediments of the Orlovka Group, which overlies Proterozoic rocks with unconformity. The felsic volcanics are essentially potassic and enriched in Rb, U, Th, and Fe. They show a weakly fractionated REE pattern with a prominent negative Eu anomaly. The basalts and picrite basalts have higher contents of Ti, Fe, P, HFSE, REE, U, Th, Ba, and Sr, and their spidergrams show no Nb or Ta depletion with respect to Th and LREE. These rocks have the petrochemical parameters of intraplate magmatic associations in continental rift zones. New geochronological data (SHRIMP II) on single zircon grains from the felsite porphyry of the metarhyolite–basalt association (717 ± 15 Ma) indicate Late Neoproterozoic volcanism in the Yenisei part of the Central block of the Trans-Angara region. According to Sm–Nd isotopic data, the rhyolites originate from Paleoproterozoic crust (TNd(DM) = 1757 Ma; TNd(DM-2st) = 1651 Ma; ∑Nd(T) = −2.7). The Orlovka volcanosedimentary rocks are rift-related, as evidenced by the following facts: (1) localization of the volcanosedimentary rocks in a narrow fault-line trough; (2) bimodal rhyolite-basaltic composition of the volcanics; and (3) petrology and geochemistry of the picrite basalts and basalts, typical of intraplate environments. The studies show that Late Neoproterozoic rifting and intraplate plume magmatism took place not only in the Tatarka–Ishimba fault zone but also in the Yenisei fault zone of the Yenisei Ridge.

Timing of Late Carboniferous/Permian Granite and Granite Porphyry Intrusions in the Ruhla Crystalline Complex (Central Germany), New Constraints from SHRIMP and 207Pb/ 206Pb Single Zircon Dating

Abstract The Ruhla Crystalline Complex (RCC) forms part of the NW trending Thuringian Forest horst block, which was affected by complex block faulting during Late Carboniferous/Early Permian times accompanied by an extensive magmatism. Block faulting results from dextral transtensive movements along the NW trending Franconian fault system, which separates the Saxo-Bohemian massif to the north from the South German block to the south. In the RCC granite bodies and a few magmatic dykes intruded along NE trending structures, whereas the majority of the magmatic dykes trend W, NW and ENE. SHRIMP zircon dating of the NE trending Trusetal Granite yielded a weighted mean age of 301 ±5 Ma, identical to a formerly presented age of 298 ±2 Ma. 207Pb/ 206Pb single zircon evaporation dating of a ductily deformed NE trending granite porphyry dyke yielded an age of 294 ±4 Ma, which is significantly older than an age of 285 ±5 Ma obtained from a WNW-trending felsite porphyry dyke. Zircon xenocrysts in the felsite porphyry gave ages of 325 ±9, 338 ±4 and 543 ±4 Ma, which indicate that crustal rocks were assimilated during magma generation and/or ascent. The presented geochronological data provide evidence that emplacement of granites and porphyry dykes along NE trending structures occured contemporaneously between 301 and 294 Ma, whereas magmatism along W to NW trending structures took place at about 285 Ma.

Post-Batholithic Geology of the La Gloria-Presa Rodríguez Area, Baja California, Mexico

Research Article| June 01, 1970 Post-Batholithic Geology of the La Gloria-Presa Rodríguez Area, Baja California, Mexico CLINTON J FLYNN CLINTON J FLYNN Humble Oil and Refining Co., Box 120, Denver, Colorado 80201 Search for other works by this author on: GSW Google Scholar Author and Article Information CLINTON J FLYNN Humble Oil and Refining Co., Box 120, Denver, Colorado 80201 Publisher: Geological Society of America Received: 24 Feb 1969 Revision Received: 16 Jan 1970 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright © 1970, The Geological Society of America, Inc. Copyright is not claimed on any material prepared by U.S. government employees within the scope of their employment. GSA Bulletin (1970) 81 (6): 1789–1806. https://doi.org/10.1130/0016-7606(1970)81[1789:PGOTLG]2.0.CO;2 Article history Received: 24 Feb 1969 Revision Received: 16 Jan 1970 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 CLINTON J FLYNN; Post-Batholithic Geology of the La Gloria-Presa Rodríguez Area, Baja California, Mexico. GSA Bulletin 1970;; 81 (6): 1789–1806. doi: https://doi.org/10.1130/0016-7606(1970)81[1789:PGOTLG]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 basement terrane of the La Gloria-Presa Rodríguez area includes Upper Jurassic and/or Lower Cretaceous intermediate-composition volcanic and derived epiclastic rocks, gabbro, granodiorite, and quartz monzonite. The post-batholithic sequence consists of conglomerates of the Upper Cretaceous Redonda Formation (new name); shales, mudstones, and sandstones of the Upper Cretaceous Rosario Formation; conglomerates, sandstones, mudstones and shales of the Eocene Buenos Aires and Delicias Formations (new names); sandstones and basalts of the Miocene Rosarito Beach Formation; and Pliocene-Pleistocene capping conglomerates and sandstones.The Upper Cretaceous Redonda Formation is composed of moderately rounded cobbles of quartzite, felsite porphyry, and volcanic breccia deposited on a high-relief Lower Cretaceous basement. The Eocene Delicias Formation is divided into a lower mudstone and an upper sandstone member. The sandstone member contains a brackish-water fauna with abundant Potamides and Ostrea. The overlying Buenos Aires Formation is divided into a lower conglomerate member and an upper sandstone member. The sandstone member contains an abundant megafauna, including characteristically tropical marine species of Turritella, Ficopsis and Tellina.The structural history of the area includes deformation and erosion of the Lower Cretaceous metavolcanic and granitic rocks followed by persistent relative stability. The overlying younger strata exhibit only low inclinations, in part to the southwest, and in part to the northeast. Post-batholithic strata are cut by numerous high-angle, northeast-southwest-trending, normal faults. Several related small anticlines and synclines are developed in the area. 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.

Stratigraphy and Sedimentology of the Woods Hollow Formation (Middle Ordovician), Trans-Pecos, Texas

The Woods Hollow Formation is a shale lithosome 400 to 500 feet thick that is part of the Ordovician sequence (2000 feet thick) in the Marathon geosyncline, Trans-Pecos, Texas. Estimated percentages of rock types in the formation are 65 percent shale, 16 percent quartzarenite, 15 percent calcarenite and 2 percent each of mudstone and conglomerate (including boulder beds). The olive-gray illite clay-shale was intensely burrowed by soft-bodied organisms; the only skeletal remains are graptolites and sponge spicules. Shale was deposited in a marine basin below surf base, probably in water several hundred feet deep. Quartzarenite and calcarenite beds 1 to 6 inches thick are intercalated through the shale and are characterized by bedding structures (grading; laminations overlain by convolute laminations and current-ripple laminations) that indicate they were deposited by waning currents of initially high velocity; these layers are probably turbidites. About 20 percent of the beds have atypical turbidite structures and possibly were transported or reworked by other marine currents. Siliciclastic and calcarenite debris (ostracods, pelmatozoans, oolites and pellets) were probably derived from Llanoria and a flanking carbonate platform to the east. Boulder-bearing shale and mudstone lenses contain clasts as much as 9 feet long. The coarse debris includes a variety of shallow-water and intertidal carbonate rock types and scarce sandstone, felsite porphyry, and schist. The boulder beds formed as plastic mass flows after the shelf to the west was uplifted and eroded to provide clasts that slid into the basins (Wilson, 1954a). Several beds near the top of the formation contain dolomite of inferred deep-water origin.

Turquoise deposits of Colorado

Colorado ranks as the second state in the production of turquois, which comes from near the towns of Villagrove, Manassa, Leadville, and Creede.The deposits occur in weathered acid igneous rocks rich in alkalic feldspar. The turquois is found as veins and nodules in faults, fissures, and cavities. The Hall mine near Villagrove is in felsite porphyry, an Oligocene volcanic flow locally cut by quartz latite. The King mine near Manassa is also in felsite porphyry, probably an extrusive member of the Miocene Santa Fe formation, which is locally cut by felsite, possibly trachyte. The Turquois Chief mine near Leadville is in the Algonkian Silver Plume granite. Turquois is found near Creede in a stream bed, but the source is unknown.The three lode deposits were formed by circulating meteoric waters that leached and concentrated the constituents of turquois from the surficial rocks and precipitated them from cold solution in fracture and shear zones. The phosphorus was probably derived from apatite; the copper, from copper ores; and the aluminum, from the alteration of feldspar; iron and silica are impurities.