scholarly journals Petrogenesis of Middle-Eocene granitoids and their Mafic microgranular enclaves in central Urmia-Dokhtar Magmatic Arc (Iran): Evidence for interaction between felsic and mafic magmas

2019 ◽  
Vol 10 (2) ◽  
pp. 705-723 ◽  
Author(s):  
Kazem Kazemi ◽  
Ali Kananian ◽  
Yilin Xiao ◽  
Fatemeh Sarjoughian
Keyword(s):  
Middle Eocene ◽  
Magmatic Arc ◽  
Microgranular Enclaves ◽  
Mafic Microgranular Enclaves ◽  
Mafic Magmas

Genesis and evolution of mafic microgranular enclaves through various types of interaction between coexisting felsic and mafic magmas

1992 ◽  
Vol 83 (1-2) ◽  
pp. 145-153 ◽  
Author(s):  
Bernard Barbarin ◽  
Jean Didier
Keyword(s):  
Chemical Exchange ◽  
Magma Chambers ◽  
Mixing Processes ◽  
Microgranular Enclaves ◽  
Mafic Microgranular Enclaves ◽  
Mass Fractions ◽  
Long Time ◽  
Mafic Magmas ◽  
The Many ◽  
Structural Levels

ABSTRACTThermal, mechanical and chemical exchange occurs between felsic and mafic magmas in dynamic magma systems. The occurrence and efficiency of such exchanges are constrained mainly by the intensive parameters, the compositions, and the mass fractions of the coexisting magmas. As these interacting parameters do not change simultaneously during the evolution of the granite systems, the exchanges appear sequentially, and affect magmatic systems at different structural levels, i.e. in magma chambers at depth, in the conduits, or after emplacement. Hybridisation processes are especially effective in the plutonic environment because contrasting magmas can interact over a long time-span before cooling. The different exchanges are complementary and tend to reduce the contrasts between the coexisting magmas. They can be extensive or limited in space and time; they are either combined into mixing processes which produce homogeneous rocks, or only into mingling processes which produce rocks with heterogeneities of various size-scales. Mafic microgranular enclaves represent the most common heterogeneities present in the granite plutons. The composite enclaves and the many types of mafic microgranular enclaves commonly associated in a single pluton, or in polygenic enclave swarms, are produced by the sequential occurrence of various exchanges between coexisting magmas with constantly changing intensive parameters and mass fractions. The complex succession and repetition of exchanges, and the resulting partial chemical and complete isotopic equilibration, mask the original identities of the initial components.

scholarly journals Crystallization Conditions and Petrogenetic Characterization of Metaluminous to Peraluminous Calc-Alkaline Orogenic Granitoids from Mineralogical Systematics: The Case of the Cambrian Magmatism from the Sierra de Guasayán (Argentina)

Minerals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 166
Author(s):  
Priscila S. Zandomeni ◽  
Juan A. Moreno ◽  
Sebastián O. Verdecchia ◽  
Edgardo G. Baldo ◽  
Juan A. Dahlquist ◽  
...  
Keyword(s):  
Mineral Chemistry ◽  
Quartz Diorite ◽  
Common Mechanism ◽  
Chemical Compositions ◽  
Magmatic Arc ◽  
Hybrid Nature ◽  
Eastern Sierras Pampeanas ◽  
Microgranular Enclaves ◽  
Mafic Microgranular Enclaves ◽  
Crystallization Conditions

The Sierra de Guasayán (Eastern Sierras Pampeanas, Argentina) is formed by low to medium grade metamorphic rocks intruded by Cambrian metaluminous (La Soledad quartz-diorite), slightly peraluminous (Guasayán, El Escondido and El Martirizado granodiorite plutons), and strongly peraluminous (Alto Bello granodiorite) granitoids of the Pampean magmatic arc. Chemical compositions of amphibole, plagioclase, biotite, and titanite indicate that these granitoids were emplaced at low pressure (mostly <3 kbar) and temperature (<770 °C) under oxidizing conditions (QFM + 1 and QFM + 2), which are similar to the emplacement conditions reported for other granites of the Pampean magmatic arc. Mineral assemblages and whole-rock and mineral chemistry of the granitoids from the Sierra de Guasayán indicate an I-type affinity for the La Soledad quartz-diorite (amphibole, biotite, and titanite), S-type affinity for the Alto Bello granodiorite (biotite, muscovite, cordierite, and sillimanite), and a hybrid nature for the main Guasayán and El Escondido plutons (biotite, monazite, and magnetite). This hybrid nature is supported by the presence of abundant mafic microgranular enclaves and rapakivi texture and by published zircon Hf-isotope data (εHfi ranging from −4.76 to −0.12). This suggests, in turn, the involvement of hybridization in the genesis of these granitoids, which seems to be a common mechanism operating in the Pampean magmatic arc.

The role of shallow open system processes in the evolution of South Tepeldag Pluton (NW Turkey): insights and constraints from thermodynamic modelling

2021 ◽  
Author(s):  
Tunahan Arık ◽  
Ömer Kamacı ◽  
Işıl Nur Güraslan ◽  
Şafak Altunkaynak
Keyword(s):  
Fractional Crystallization ◽  
Open System ◽  
Suture Zone ◽  
Thermodynamic Simulations ◽  
Nw Turkey ◽  
Microgranular Enclaves ◽  
Mafic Microgranular Enclaves ◽  
Ophiolitic Rocks ◽  
Compositional Variations ◽  
Spider Diagrams

&lt;p&gt;Eocene granitoids in NW Anatolia occurred following the continental collision between Sakarya Continent and Tauride-Anatolide Platform and mark the onset of post-collisional magmatism in the region. One of the representative members of the Eocene granitoids, the Tepelda&amp;#287; pluton crops out as two isolated granitic bodies and is intruded into the Cretaceous blueschist assemblages (Kocasu formation) and ophiolitic rocks within the Izmir-Ankara-Erzincan suture zone (IAESZ). South Tepelda&amp;#287; pluton (STP) is composed mainly of granodiorite with subordinate quartz diorite, which show transitional contacts. Aplitic dykes crosscut the pluton as well as the country rocks. STP includes a number of mafic microgranular enclaves (MME) of gabbro/diorite composition.&lt;/p&gt;&lt;p&gt;Geochemically, STP shows distinct I-type affinity with a metaluminous to slightly peraluminous (ASI &amp;#8804;1.02) nature. The samples are medium-K to high-K calc-alkaline in character. They exhibit depletion in HFSE (Ti, Hf, Zr, Nb and Ta) compared to large ion lithophile elements (Rb, Ba, Th, U, K) and presents negative Nb, P, Ti anomalies. STP displays slight negative Eu anomalies (Eu/Eu* = 0.7&amp;#8211;1.2), enrichment in LREE and flat HREE patterns in chondrite-normalized spider diagrams. MELTS modeling (with initial parameters of 1&amp;#8211;3 kbar pressure, 2&amp;#8211;3% water and QFM-NNO oxygen fugacity buffers) indicate that compositional variations in STP samples can be interpreted as a result of open system processes (assimilation fractional crystallization) rather than a reflection of fractional crystallization in the upper crustal magma chamber. All thermodynamic simulations dictate a crustal assimilation, especially in the late stages of the magmatic process, with a MgO, Na&lt;sub&gt;2&lt;/sub&gt;O and Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;-rich assimilant similar to the suture zone (IAESZ) rocks.&lt;/p&gt;

Insights into granite petrogenesis from quantitative assessment of the field distribution of enclaves, xenoliths and K-feldspar megacrysts in the Monte Capanne pluton, Italy

2008 ◽  
Vol 72 (4) ◽  
pp. 925-940 ◽  
Author(s):  
D. Gagnevin ◽  
J. S. Daly ◽  
G. Poli
Keyword(s):  
Field Study ◽  
Magma Chamber ◽  
Late Stage ◽  
Field Data ◽  
Quantitative Assessment ◽  
Mafic Magma ◽  
Crustal Assimilation ◽  
Microgranular Enclaves ◽  
Mafic Microgranular Enclaves ◽  
Quantitative Analyses

AbstractA detailed field study to determine quantitatively the distribution of K-feldspar megacrysts, mafic microgranular enclaves (MME) and metasedimentary xenoliths has been carried out in the Monte Capanne pluton (Elba, Italy) with a view to evaluating the utility of this approach to petrogenetic investigations. Mafic microgranular enclaves are inferred to result from interactions between mafic and felsic magmas, while xenoliths attest to crustal assimilation occurring in the Monte Capanne magma chamber. In particular, we emphasize, based on our field data, that both processes are intimately linked, such that xenolith dissolution during assimilation was triggered by replenishment with hot mafic magma. It is suggested that the previously defined ‘San Piero’ and ‘San Francesco’ facies do not differ substantially, and are thus amalgamated and renamed as the ‘Pomonte’ facies. Results also indicate that the abundance of K-feldspar megacrysts is positively correlated with the volumetric abundance of MME in the Sant’ Andrea facies, which we link to a recharging, mingling and textural coarsening event that occurred at a rather late stage of magma-chamber evolution prior to emplacement. This study demonstrates how petrogenetic processes can be deciphered by detailed field quantitative analyses of granite-forming components, thus complementing geochemical investigations.

Anisian granodiorites and mafic microgranular enclaves in the eastern Kunlun Orogen, NW China: Insights into closure of the eastern Paleo–Tethys

2020 ◽  
Vol 55 (9) ◽  
pp. 6487-6507
Author(s):  
Yanjun Li ◽  
Junhao Wei ◽  
M. Santosh ◽  
Huan Li ◽  
Huiwen Liu ◽  
...  
Keyword(s):  
Nw China ◽  
Microgranular Enclaves ◽  
Mafic Microgranular Enclaves
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