Geologic framework and geochronology of ultramafic complexes of southern Mexico

1992 ◽  
Vol 29 (7) ◽  
pp. 1590-1604 ◽  
Author(s):  
L. A. Delgado-Argote ◽  
M. López-Martínez ◽  
D. York ◽  
C. M. Hall
Keyword(s):  
Ultramafic Rocks ◽  
Southern Mexico ◽  
Structural Trend ◽  
Sedimentary Sequences ◽  
San Pedro ◽  
Intrusive Rocks ◽  
Accreted Terranes ◽  
Granitoid Rocks ◽  
Geologic Setting ◽  
Metamorphic Complexes

In southern Mexico, discrete ultramafic intrusive bodies larger than 4 km2 are genetically related to their enclosing volcano-sedimentary terranes. These terranes are the Cuicateco and Guerrero, which include the Cuicateco and Tierra Caliente metamorphic complexes, respectively. Their basement is largely unknown, and the ultramafic masses previously have been interpreted as allochthonous dismembered ophiolites. To constrain the age of these accreted terranes, the geologic setting and 40Ar/39Ar ages are presented from the localities of Loma Baya – El Tamarindo, Guerrero, and San Pedro Limón, State of México, in the Tierra Caliente Complex, and Teotitlán – Conceptión Pápalo, Oaxaca, in the Cuicateco Complex. The Teotitlán – Conceptión Pápalo area is characterized by a sequence of metamorphosed intermediate granitoid rocks, andesitic lavas, tuffs, and psammites. The intrusive rocks and lavas are pervasively mylonitized and show abundant ultramafic segregations. The largest ultramafic bodies were emplaced into metatuffs, following the regional east-verging structural trend. Three hornblende separates from a hornblende diorite and one from a hornblende-rich clinopyroxenite yielded plateau ages of ca. 130 Ma. The ultramafic rocks in the Tierra Caliente Complex lack orthopyroxene and transitionally grade outward into hornblende diorites. The El Tamarindo ultramafic body (4.6 km2) rose as a diapir into an Albian volcano-sedimentary sequence. The best estimate for the age of this body is ca. 112 Ma from a hornblende separated from a pegmatite dike sample. This age is similar to the Albian fauna reported at Zihuatanejo and other K–Ar ages from ultramafic rocks at Camalotitos. The rigid and poorly serpentinized San Pedro Limon Stock (15 km2) was vertically emplaced into the Xochipala Formation (Cenomanian) during a regional Neogene transpressive disturbance. Four hornblende samples from hornblende clinopyroxenites and hornblendites yielded remarkably flat age spectra, indicating an age of ca. 105 Ma for the San Pedro Limon Stock. Based on the good correlation between the 40Ar/39Ar ages reported here and earlier faunistic data, it is concluded that the ultramafic rocks cooled penecontemporaneously with the deposition of the enclosing volcano-sedimentary sequences.

scholarly journals The 1590-1520 Ma Cachoeirinha magmatic arc and its tectonic implications for the Mesoproterozoic SW Amazonian craton crustal evolution

2004 ◽  
Vol 76 (4) ◽  
pp. 807-824 ◽  
Author(s):  
Amarildo S. Ruiz ◽  
Mauro C. Geraldes ◽  
João B. Matos ◽  
Wilson Teixeira ◽  
William R. Van Schumus ◽  
...  
Keyword(s):  
Crystallization Process ◽  
Major And Trace Elements ◽  
Magmatic Arc ◽  
Rio Negro ◽  
Intrusive Rocks ◽  
Amazonian Craton ◽  
Granitoid Rocks ◽  
Geologic Setting ◽  
Fractional Crystallization Process ◽  
Tectonic Relationship

Isotopic and chemical data of rocks from the Cachoeirinha suite provide new insights on the Proterozoic evolution of the Rio Negro/Juruena Province in SW Amazonian craton. Six U-Pb and Sm-Nd analyses in granitoid rocks of the Cachoeirinha suite yielded ages of 1587-1522 Ma and T DM model ages of 1.88-1.75 Ga (EpsilonNd values of -0.8 to +1.0). In addition, three post-tectonic plutonic rocks yielded U-Pb ages from 1485-1389 Ma (T DM of 1.77-1.74 Ga and EpsilonNd values from -1.3 to +1.7). Variations in major and trace elements of the Cachoeirinha suite rocks indicate fractional crystallization process and magmatic arc geologic setting. These results suggest the following interpretations: (1) The interval of 1590-1520 Ma represents an important magmatic activity in SW Amazonian craton. (2) T DM and arc-related chemical affinity supportthe hypothesis that the rocks are genetically associated with an east-dipping subduction zone under the older (1.79-1.74 Ga) continental margin. (3) The 1590-1520 Ma age of intrusive rocks adjacent to an older crust represents similar geological framework along the southern margin of Baltica, corroborating the hypothesis of tectonic relationship at that time.

scholarly journals Geologic Setting of Eclogite-facies Assemblages in the St. Cyr Klippe, Yukon–Tanana Terrane, Yukon, Canada

2015 ◽  
Vol 42 (3) ◽  
pp. 327 ◽  
Author(s):  
Meredith Blair Petrie ◽  
Jane A. Gilotti ◽  
William C. McClelland ◽  
Cees Van Staal ◽  
Sierra J. Isard
Keyword(s):  
High Pressure ◽  
Ultramafic Rocks ◽  
South Central ◽  
Continental Arc ◽  
Intrusive Rocks ◽  
Eclogite Facies ◽  
Tectonic Mélange ◽  
Geologic Setting ◽  
Host Rocks

The St. Cyr area near Quiet Lake hosts well preserved to variably retrogressed eclogite found as sub-metre to hundreds of metre-long lenses within quartzofeldspathic schist in south-central Yukon, Canada. The St. Cyr klippe consists of structurally imbricated, polydeformed and polymetamorphosed units of continental arc crust and ultramafic–mafic rocks. Eclogite-bearing quartzofeldspathic schist forms thrust slices in a 30 km long by 6 km wide, northwest-striking outcrop belt. The schist unit comprises metasedimentary and felsic intrusive rocks that are intercalated on the metre to tens of metres scale. Ultramafic rocks, serpentinite and associated greenschist-facies metagabbro form imbricated tectonic slices within the eclogite-bearing quartzofeldspathic unit, which led to a previously held hypothesis that eclogite was exhumed within a tectonic mélange. The presence of phengite and Permian zircon crystallized under eclogite-facies metamorphic conditions in the quartzofeldspathic host rocks indicate that the eclogite was metamorphosed in situ together with the schist as a coherent unit that was part of the continental arc crust of the Yukon–Tanana terrane, rather than a mélange associated with the subduction of oceanic crust of the Slide Mountain terrane. Petrological, geochemical, geochronological and structural similarities link St. Cyr eclogite to other high-pressure localities within Yukon, indicating the high-pressure assemblages form a larger lithotectonic unit within the Yukon–Tanana terrane.RÉSUMÉLa région de St-Cyr renferme des éclogites bien conservées à légèrement rétrogradées qui se présentent sous forme de lentilles allant de la fraction de mètre à quelques centaines de mètres de longueur, au sein d’un schiste quartzofeldspathique du centre-sud du Yukon au Canada. La klippe de St-Cyr est structurellement constituée d’unités imbriquées, polydéformées et polymétamorphisées de croûte d’arc continental et de roches ultramafiques à mafiques. Les schistes quartzofeldspathiques à lentilles d’éclogites forment des écailles de chevauchement d’une bande de 30 km de longueur par 6 km de largeur de direction nord-ouest. Les schistes sont constitués de roches métasédimentaires et de roches intrusives felsiques intercalées à des intervalles qui vont du mètre à quelques dizaines de mètres. Les roches ultramafiques, serpentinites et métagabbros au facies à schiste vert forment des écailles tectoniques imbriquées au sein de l’unité quartzofeldspathique à lentilles d’éclogite, d’où une précédente hypothèse voulant que les éclogites soient un produit d’exhumation à partir d’un mélange tectonique. La présence de phengite et de zircon permien cristallisé sous conditions métamorphiques du faciès à éclogite au sein de la roche hôte quartzofeldspathique indiquent que l’éclogite a été métamorphisée en place, avec le schiste comme unité cohérente du terrane de croûte d’arc continental de Yukon–Tanana, plutôt qu’un mélange associé à une subduction de croûte océanique du terrane de Slide Mountain. Des similarités pétrologiques, géochimiques, géochronologiques et structurales lient les éclogites de St-Cyr à d’autres lieux de hautes pressions au Yukon, ce qui indique que les assemblages de hautes pressions forment une unité lithotectonique plus grande au sein du terrane de Yukon–Tanana.

ARCHAEAN SEDIMENTARY ROCKS OF NORTH SPIRIT LAKE AREA, NORTHWESTERN ONTARIO

1965 ◽  
Vol 2 (6) ◽  
pp. 622-647 ◽  
Author(s):  
J. A. Donaldson ◽  
G. D. Jackson
Keyword(s):  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Sole Source ◽  
Lake Area ◽  
Red Lake ◽  
Sedimentary Sequences ◽  
The North ◽  
Northwestern Ontario ◽  
History Of ◽  
Granitoid Rocks

Archaean sedimentary rocks of the North Spirit Lake area show little evidence of having been derived predominantly from associated Archaean volcanic rocks. Instead, compositions of the sediments reflect significant sedimentary and (or) granitoid provenance. A remarkably high content of clastic quartz in thick units of sandstone and conglomerate suggests either reworking of older quartzose sediments, or reduction of the labile constituents in quartz-rich granitoid rocks through prolonged weathering and rigorous transport. Observations for other sedimentary sequences in the region between Red Lake and Lansdowne House suggest that the North Spirit sediments are not unique in the Superior Province. Quartzose sandstones commonly are regarded as atypical of the Archaean, but such rocks arc abundant in northwestern Ontario. Frameworks of many Archaean greywackes actually are richer in quartz than typical greywackes from numerous Proterozoic and Phanerozoic sequences.The concept of rapidly rising volcanic arcs as the sole source of Archaean sedimentary detritus is rejected for the North Spirit area. The volcanies, rather than representing relicts of protocontinents, probably record events removed from initial volcanism in the history of the earth by one or more orogenic cycles. Major unconformities may therefore exist not only between sedimentary and volcanic units, but also between these units and older granitoid rocks.

scholarly journals High-Temperature Metamorphic Garnets from Grenvillian Granulites of Southwestern Oaxacan Complex (Southern Mexico): Petrology, Geochemistry, Geothermobarometry, and Tectonic Implications

Minerals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 805
Author(s):  
Laura Culí ◽  
Jesús Solé ◽  
Marc Campeny ◽  
Jeffry A. G. Oalmann
Keyword(s):  
Granulite Facies ◽  
Ultramafic Rocks ◽  
Southern Mexico ◽  
Grain Sizes ◽  
Mineral Phases ◽  
Northeastern Mexico ◽  
Almost All ◽  
Structural Levels ◽  
First Time ◽  
Rule Out

The basement of eastern Mexico comprises Grenvillian-age granulite-facies metamorphic rocks. The Oaxacan Complex represents the largest outcrop belt of this basement in Mexico. In this work, southwestern Oaxacan Complex garnets are studied from a petrographical, geochemical, and geothermobarometrical perspective for the first time. The studied garnets display different grain sizes nucleated in a polyphase evolution. The almandine end member proportion is similar in all of the studied lithotypes. The highest pyrope concentrations are found in Qz Fsp paragenesis and ultramafic rocks and the lowest pyrope concentrations are found in amphibolite. The highest grossular and spessartine concentrations are found in the amphibolite lithotype. Southwestern Oaxacan Complex garnets from paraderivate samples are more enriched in Rb, Ba, Pb, Ni, and Zn than those from orthoderivate samples enriched in Ti and V. This fact is related to the nature of the protoliths and the mineral phases that fractionate the same minor and trace elements. Garnets from para- and orthoderivate samples display 0.02–1.1 Eu/Eu* anomalies. This fact indicates that almost all of the garnets formed while the plagioclase was stable, and it does not rule out the interpretation that some garnets were peritectic. The pressure obtained using a Grt-Opx-Pl-Qz geobarometer in the southwestern Oaxacan Complex is higher than the pressure obtained in the northern part of the Complex, and it is consistent with the pressure obtained in the Grenvillian-age granulites of the Novillo Gneiss from northeastern Mexico. Geothermobarometric studies reveal different P-T features at the study site, so different structural levels of the orogen are inferred.

U–Pb zircon ages for rocks from the Island Lake greenstone belt, Manitoba

1986 ◽  
Vol 23 (1) ◽  
pp. 92-101 ◽  
Author(s):  
A. Turek ◽  
T. M. Carson ◽  
Patrick E. Smith ◽  
W. R. Van Schmus ◽  
W. Weber
Keyword(s):  
Greenstone Belt ◽  
Quartz Diorite ◽  
Superior Province ◽  
Intrusive Complex ◽  
Quartz Porphyry ◽  
Zircon Age ◽  
Metasedimentary Rocks ◽  
Intrusive Rocks ◽  
Granitoid Rocks

The Archean Hayes River Group of the Island Lake greenstone belt (Superior Province, Sachigo Subprovince) comprises mafic to felsic metavolcanics, subvolcanics, and associated metasedimentary rocks. The Hayes River Group is intruded by granitoid rocks belonging to the early intrusive complex. One such pluton, the Bella Lake tonalite, is intrusive into the metabasalt of the Hayes River Group and has a U–Pb zircon age of 2886 ± 15 Ma. Similar intrusives of this complex, either internal or marginal to the greenstone belt, yield zircon ages of 2801 ± 8 Ma (Pipe Point tonalit) and 2768 ± 22 Ma (Linklater Island prophyry). This suggests that the early intrusive complex was emplaced over an ~ 120 Ma long interval by at least three separate intrusive episodes.Subsequent to the emplacement of the early intrusive complex, the isoclinally folded Hayes River Group and the early intrusive complex were uplifted, eroded, and followed by the unconformable deposition of the Island Lake Group, comprising fluvial to marine metasedimentary rocks. The stratigraphically lower part of the Island Lake Group is bracketed by the 2768 ± 22 Ma age of the Linklater Island porphyry and the 2729 ± 3 Ma age obtained for the late tectonic suite—the Pipe Point quartz diorite and feldspar porphyry. A feldspar quartz porphyry belonging to the post-tectonic intrusive rocks intrudes higher stratigraphic levels and has been dated at 2699 ± 4 Ma (Horseshoe Island quartz feldspar porphyry).

K–Ar and 40Ar/39Ar geochronology of granitoid rocks from southern Nova Scotia: Its bearing on the geological evolution of the Meguma Zone of the Appalachians

1981 ◽  
Vol 18 (2) ◽  
pp. 386-394 ◽  
Author(s):  
P. H. Reynolds ◽  
M. Zentilli ◽  
G. K. Muecke
Keyword(s):  
Nova Scotia ◽  
Age Distribution ◽  
Distribution Patterns ◽  
Data Set ◽  
South Mountain Batholith ◽  
A Value ◽  
Intrusive Rocks ◽  
Geological Evolution ◽  
Granitoid Rocks ◽  
Apparent Age

K–Ar and (or) 40Ar/39Ar apparent ages are reported for 28 samples of biotite and muscovite from Nova Scotia's South Mountain batholith and associated northern satellite stocks. In addition, 14 mica samples from the southern satellite stocks were dated. Previous workers, using primarily K–Ar and Rb/Sr techniques, have reported a spread of apparent ages ranging from ~240–420 Ma for these intrusive rocks. The present data set is internally consistent and has been calibrated against accepted interlaboratory standards. A mean age of 367 Ma was obtained for the South Mountain batholith and the northern stocks, a value consistent with results recently obtained in an Rb/Sr study by Clarke and Halliday. No differences in apparent age among the various phases or clear geographic age distribution patterns were evident. Satellite stocks in the southern part of the province have, in general, younger apparent ages clustered in the range ~300–320 Ma. We suggest that in southern areas mica–argon systems record the effects of a Late Carboniferous intrusive and (or) thermotectonic event. This conclusion may have important metallogenic implications.

scholarly journals Epizonal I- and A-type granites and associated ash-flow tuffs, Fogo Island, northeast Newfoundland

1995 ◽  
Vol 32 (11) ◽  
pp. 1835-1844 ◽  
Author(s):  
Hamish A. Sandeman ◽  
John Malpas
Keyword(s):  
Alkali Feldspar ◽  
Granitic Rocks ◽  
Calc Alkaline ◽  
Fine Grained ◽  
Sedimentary Sequences ◽  
Intrusive Rocks ◽  
High Silica ◽  
Composite Nature ◽  
End Members ◽  
Devonian Age

Magmatic activity of Silurian–Devonian age is widespread in the Appalachian–Caledonian Orogen. A marked characteristic of this magmatism is the composite nature of the igneous suites, which range from peridotite to granodiorite in single plutonic bodies. The origin of these suites is still enigmatic, and the assumption that all are the same not proven. Such a suite of intrusive rocks, ranging in composition from minor peridotite to granodiorite, intrudes an openly folded sequence of Silurian volcanogenic sandstones and ash-flow tuffs on Fogo Island, northeast Newfoundland. Two units, the Rogers Cove and Hare Bay microgranites, consist of fine-grained hastingsite granites with spherulitic and flow-banded textures, and exhibit drusy cavities and microfractures that contain the mineral assemblage hastingsitic hornblende + plagioclase + magnetite + zircon. These rocks are characterized by elevated high field strength element contents (e.g., Zr = 74–672 and Y = 21–103 ppm), very high FeO*/MgO ratios (FeO*/MgO = 2.4–93.5), and 10 000 Ga/Al ratios of 1.67–10.52, indicating an A-type granitoid affinity. A third and the most voluminous granitic unit, the Shoal Bay granite, is an alkali-feldspar-phyric, medium-grained, equigranular biotite–hastingsite granite with hastingsite and annitic biotite interstitial to euhedral plagioclase, anhedral quartz, and perthite crystals. The Shoal Bay granite exhibits mineral parageneses similar to the microgranites, but chemical characteristics more typical of calc-alkaline, I-type granitoids. Volcanic–sedimentary sequences spatially associated with the granitic rocks include dense, welded, high-silica, hastingsite-bearing ash-flow tuffs with compositions that suggest they represent erupted equivalents of fractionated end members of the Shoal Bay granite. The rocks making up the Fogo Island batholith have been directly equated with the bimodal, calc-alkaline Mount Peyton batholith of northeast Newfoundland, but the specialized A-type nature of the Fogo granites suggests differing source conditions for the two suites.

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