scholarly journals Volatile elements in alkaline and calc-alkaline rocks from the Colima graben, Mexico: Constrains on their genesis and evolution

1993 ◽  
Vol 32 (4) ◽  
pp. 575-589
Author(s):  
José Luís Macías ◽  
Bruno Capaccioni ◽  
Sandro Conticelli ◽  
Marino Martini ◽  
Sergio Rodríguez
Keyword(s):  
Calc Alkaline ◽  
Volatile Elements ◽  
Alkaline Rocks ◽  
Los Grupos

Tomando esencialmente como base la composición química de los elementos mayores, tres diferentes grupos de rocas fueron reconocidos en el graben de Colima. El grupo alcalino, calcialcalino y calcialcalino rico en potasio. Dichos grupos fueron originados a partir de diferentes magmas primitivos. El primero de ellos está compuesto por traquibasaltos y de todas las muestras estudiadas, es el que cuenta con las más altas concentraciones en elementos compatibles, elementos incompatibles, potasio y fluor. De los tres grupos, el grupo calcialcalino representado por andesitas y dacitas es el que tiene el más amplio rango en composición debido probablemente a procesos evolutivos de baja presión. El último grupo reconocido (calcialcalino rico en potasio) está formado por andesitas y dacitas ricas en potasio y yace entre los grupos alcalino y calcialcalino. En los grupos calcialcalino y calcialcalino rico en potasio no se encontraron rocas primitivas. Los elementos hidromagmatófilos tienen patrones similares en todas las muestras estudiadas con valores altos de LILE/HFSE. El análisis de los elementos volátiles (F, Cl, S, C) muestra que C y S se encuentran en bajas concentraciones en las rocas básicas de los tres grupos y no presentan tendencias evolutivas significativas; Cl y F son inicialmente bajos en las rocas básicas de los grupos calcialcalinos y calcialcalino rico en potasio y tienden a incrementarse con el grado de evolución. Sin embargo, debido a la exsolución en la cámara magmática a poca profundidad algunas muestras perdieron estos dos halógenos. Es importante hacer notar que las rocas alcalinas tienen concentraciones iniciales de F y K2O muy superiores a las encontradas en las rocas primitivas de los otros dos grupos. Puede asumirse que un manto rico en micas probablemente flogopita, afectado por diferentes grados de fusión parcial, dio origen a los diferentes grupos de rocas encontrados en el área de Colima. Sin embargo esta es sólo una hipótesis de trabajo. Para poder entender los diferentes procesos evolutivos que dieron lugar a las rocas estudiadas, un mayor número de estudios mineralógicos, petrológicos y geoquímicos necesitan ser realizados.

scholarly journals Magma Mixing Genesis of the Mafic Enclaves in the Qingshanbao Complex of Longshou Mountain, China: Evidence from Petrology, Geochemistry, and Zircon Chronology

Minerals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 195 ◽  
Author(s):  
Wenheng Liu ◽  
Xiaodong Liu ◽  
Jiayong Pan ◽  
Kaixing Wang ◽  
Gang Wang ◽  
...  
Keyword(s):  
Host Rock ◽  
Inductively Coupled Plasma ◽  
Magma Mixing ◽  
Coarse Grained ◽  
Calc Alkaline ◽  
Quartz Crystals ◽  
Alkaline Rocks ◽  
Mafic Enclaves ◽  
Normal Zoning ◽  
Host Rocks

The Qingshanbao complex, part of the uranium metallogenic belt of the Longshou-Qilian mountains, is located in the center of the Longshou Mountain next to the Jiling complex that hosts a number of U deposits. However, little research has been conducted in this area. In order to investigate the origin and formation of mafic enclaves observed in the Qingshanbao body and the implications for magmatic-tectonic dynamics, we systematically studied the mineralogy, petrography, and geochemistry of these enclaves. Our results showed that the enclaves contain plagioclase enwrapped by early dark minerals. These enclaves also showed round quartz crystals and acicular apatite in association with the plagioclase. Electron probe analyses showed that the plagioclase in the host rocks (such as K-feldspar granite, adamellite, granodiorite, etc.) show normal zoning, while the plagioclase in the mafic enclaves has a discontinuous rim composition and shows instances of reverse zoning. Major elemental geochemistry revealed that the mafic enclaves belong to the calc-alkaline rocks that are rich in titanium, iron, aluminum, and depleted in silica, while the host rocks are calc-alkaline to alkaline rocks with enrichment in silica. On Harker diagrams, SiO2 contents are negatively correlated with all major oxides but K2O. Both the mafic enclaves and host rock are rich in large ion lithophile elements such as Rb and K, as well as elements such as La, Nd, and Sm, and relatively poor in high field strength elements such as Nb, Ta, P, Ti, and U. Element ratios of Nb/La, Rb/Sr, and Nb/Ta indicate that the mafic enclaves were formed by the mixing of mafic and felsic magma. In terms of rare earth elements, both the mafic enclaves and the host rock show right-inclined trends with similar weak to medium degrees of negative Eu anomaly and with no obvious Ce anomaly. Zircon LA-ICP-MS (Laser ablation inductively coupled plasma mass spectrometry) U-Pb concordant ages of the mafic enclaves and host rock were determined to be 431.8 5.2 Ma (MSWD (mean standard weighted deviation)= 1.5, n = 14) and 432.8 4.2 Ma (MSWD = 1.7, n = 16), respectively, consistent with that for the zircon U-Pb ages of the granite and medium-coarse grained K-feldspar granites of the Qingshanbao complex. The estimated ages coincide with the timing of the late Caledonian collision of the Alashan Block. This comprehensive analysis allowed us to conclude that the mafic enclaves in the Qingshanbao complex were formed by the mixing of crust-mantle magma with mantle-derived magma due to underplating, which caused partial melting of the ancient basement crust during the collisional orogenesis between the Alashan Block and Qilian rock mass in the early Silurian Period.

Petrographic, Geochemical and Isotopic (Sr–Nd–Pb–Os) Study of Plio-Quaternary Volcanics and the Tertiary Basement in the Jorullo-Tacámbaro Area, Michoacán-Guanajuato Volcanic Field, Mexico

2019 ◽  
Vol 60 (12) ◽  
pp. 2317-2338 ◽  
Author(s):  
Marie-Noëlle Guilbaud ◽  
Claus Siebe ◽  
Christine Rasoazanamparany ◽  
Elisabeth Widom ◽  
Sergio Salinas ◽  
...  
Keyword(s):  
Trace Element ◽  
Crustal Contamination ◽  
Volcanic Belt ◽  
Volcanic Field ◽  
Calc Alkaline ◽  
Trace Element Pattern ◽  
Alkaline Rocks ◽  
Rock Types ◽  
Oceanic Sediments ◽  
Element Pattern

Abstract The origin of the large diversity of rock types erupted along the subduction-related Trans-Mexican Volcanic Belt (TMVB) remains highly debated. In particular, several hypotheses have been proposed to explain the contemporary eruption of calc-alkaline and alkaline magmas along the belt. The Michoacán-Guanajuato Volcanic Field (MGVF) is an atypical, vast region of monogenetic activity located in the western-central part of the TMVB. Here we present new petrographic, geochemical, and isotopic (Sr–Nd–Pb–Os) data on recent volcanics in the Jorullo-Tacámbaro area that is the closest to the oceanic trench. TMVB-related volcanics in this area are Plio-Quaternary (<5 Ma) and mainly form a calc-alkaline series from basalts to dacites, with rare (<5 vol. %) alkaline rocks that range from trachybasalts to trachydacites, and transitional samples. Crystal textures are consistent with rapid crystallization at shallow depth and processes of mixing of similar magma batches (magma recharge). All of the samples exhibit an arc-type trace element pattern. Alkaline and transitional magmas have higher Na2O and K2O, lower Al2O3, and higher concentrations in incompatible elements (e.g. Sr, K, Ba, Th, Ce, P) compared to calc-alkaline rocks. Calc-alkaline rocks are similar isotopically to transitional and alkaline samples, except for a few low 87Sr/86Sr samples. Sr, Nd and Pb isotopes do not correlate with MgO or 187Os/188Os, indicating that they were not significantly influenced by crustal contamination. Isotopic and trace-element systematics suggest that the Tacámbaro magmas are produced by melting of a mantle wedge fluxed by fluids derived from a mixture of subducted sediments and altered oceanic crust. Alkaline and transitional magmas can be derived from a lower degree of partial melting of a similar source to that of the calc-alkaline rocks, whereas the few low 87Sr/86Sr calc-alkaline rocks require a lower proportion of fluid derived from oceanic sediments and crust. Volcanism at the trenchward edge of the MGVF was thus driven purely by subduction during the last 5 Ma, hence discarding slab rollback in this sector of the TMVB.

scholarly journals Calc-alkaline rocks

2006 ◽  
pp. 78-81
Author(s):  
J. SouČek ◽  
F. V. Holub ◽  
E. JelÍnek ◽  
H. KlÁpovÁ
Keyword(s):  
Calc Alkaline ◽  
Alkaline Rocks

scholarly journals Primitive tholeiites and calc-alkaline rocks from Hahajima, Bonin (Ogasawara) archipelago.

2001 ◽  
Vol 30 (4) ◽  
pp. 164-179 ◽  
Author(s):  
Kazuhito YAJIMA ◽  
Hirokazu FUJIMAKI ◽  
Naoshi KURODA
Keyword(s):  
Calc Alkaline ◽  
Alkaline Rocks

Metasomatic and Intrusive nepheline-bearing rocks from the Mbozi syenite-gabbro complex, southwestern Tanzania

1968 ◽  
Vol 5 (3) ◽  
pp. 387-419 ◽  
Author(s):  
P. W. G. Brock
Keyword(s):  
Volume Change ◽  
Nepheline Syenite ◽  
Color Index ◽  
Ring Structure ◽  
Standard Cell ◽  
Volatile Elements ◽  
Alkaline Rocks ◽  
Northeastern Flank ◽  
Basic Rocks

The Mbozi Complex (20 × 8 miles) is situated on the Great North Road 15 miles east of the Tanzania–Zambia border. It is at least 743 million years old, and is emplaced in Ubendian Gneisses (1800 m.y.) along the northeastern flank of the Tunduma Rift.The oldest rocks in the complex are layered calcic gabbros, with cumulates of iron-rich pyroxenite and bytownite anorthosite. The basic rocks were faulted and deformed prior to the emplacement of alkaline rocks around the perimeter of the complex. The alkaline rocks are saturated with respect to silica near the ends of the complex, but are nepheline-bearing near the center. The larger masses of marginal syenite are magmatic intrusions.Within the basic rocks near the center of the complex is an elliptical zone of feldspathoidal rocks surrounding a core of unaltered gabbro. The rocks in this ring structure are heterogeneous, ranging in composition from slightly altered gabbro, through all intermediate compositions to ijolite, litchfieldite, and rutterite. They have well-developed concentric banding, but vary rapidly in composition and texture along and across strike. Contacts are gradational. The majority of the ring rocks appear to be metasomatized gabbros, but a few persistant, concordant bands of homogeneous litchfieldite are probably intrusive.Assuming no volume change and little change in color index, metasomatism of gabbroic rocks to produce the ring rocks would involve introduction of cations to the standard cell of 160 O ions in the proportion K5 – 9 Na21 – 27 Al−2 – +5 Si−5 – +11 P0 – +4 and removal of Ca14 – 21 Mg11 – 15 Fe2 – 4Ti1 – 2.It is concluded that the ring structure developed above a volatile-rich nepheline syenite, and that the metasomatism was effected by the volatile elements of that magma.

The Silurian volcanic rocks of the Mendip Hills, Somerset; and the Tortworth area, Gloucestershire, England

1969 ◽  
Vol 106 (6) ◽  
pp. 542-553 ◽  
Author(s):  
P. C. van De Kamp
Keyword(s):  
Base Metal ◽  
Rock Type ◽  
Volcanic Rocks ◽  
Calc Alkaline ◽  
Metal Concentrations ◽  
Alkaline Rocks ◽  
Dolerite Dyke ◽  
Chemical Studies

SUMMARYField, petrographic and chemical studies on the Silurian volcanic rocks of the Mendip Hills show that there are probably 15 or more rock units in the series including andesite and rhyodacite lavas, rhyodacite tuffs, agglomerates, and a dolerite dyke. The predominant rock type is rhyodacite which may be as much as 80 percent of the volcanics. Volcanics of Silurian age from the Tortworth area, Gloucestershire, are of latite-andesite composition.The Mendip rocks have been deuterically altered. Calcite-quartz-laumontite veins are common in fractures in these rocks. The agglomerates are particularly susceptible to weathering and some bombs are extensively altered to clays. Twelve rocks were chemically analysed for 36 elements each. No anomalous base metal concentrations were found in the volcanics although Pb, Zn, and Cu mineralisation is known in the area. K/Rb varies from 202 to 909 in these calc-alkaline rocks.

Mineralogical–geochemical constraints on intrusives in central Anatolia, Turkey: tectono-magmatic evolution and characteristics of mantle source

2005 ◽  
Vol 142 (2) ◽  
pp. 187-207 ◽  
Author(s):  
N. İLBEYLİ
Keyword(s):  
Mantle Source ◽  
Central Anatolia ◽  
Alkaline Magmatism ◽  
Calc Alkaline ◽  
Alkaline Rocks ◽  
Rock Types ◽  
Slab Breakoff ◽  
Wide Range ◽  
Cretaceous Magmatism ◽  
Geochemical Constraints

Collision-related rocks intrude metamorphic rocks overthrust by ophiolitic units to make up the Central Anatolian Crystalline Complex. A wide variety of rock types were produced by the latest Cretaceous magmatism in the complex. These rocks can be divided into three distinct units: (1) calc-alkaline (Ağaçören, Behrekdağ, Cefalıkdağ, Çelebi, Ekecikdağ, Halaçlı, Karamadazı, Kösefakılı, Terlemez, Üçkapılı, Yozgat); (2) sub-alkaline (Baranadağ); and (3) alkaline (Atdere, Davulalan, Eğrialan, Hamit, İdişdağı, Karaçayır). The calc-alkaline rocks are metaluminous/peraluminous I- to S-type plutons ranging from monzodiorite to granite. The sub-alkaline rocks are metaluminous I-type plutons ranging from monzonite to granite. The alkaline rocks are metaluminous to peralkaline plutons, predominantly A-type, ranging from foid-bearing monzosyenite to granite. These plutons crystallized under varying pressures (5.3–2.6 kbar) and a wide range of temperatures (858–698 °C) from highly oxidized magmas (log fO2 −17 to −12). All intrusive rocks display enrichment in LILE and LREE compare to HFSE and have high 87Sr/86Sr and low 143Nd/144Nd ratios. These characteristics indicate that these rocks are derived from a mantle source containing large subduction components, and have experienced assimilation coupled with fractional crystallization (AFC) during uprise through crust. The coexistence of calc-alkaline and alkaline magmatism in the complex may be ascribed to mantle source heterogeneity before collision. Either thermal perturbation of the metasomatized lithosphere by delamination of the thermal boundary layer or removal of a subducted plate (slab breakoff) are the likely mechanisms for the initiation of the collision-related magmatism in the complex.

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