Petrogenesis and Geochronology of the late-Archean Na-rich A Type granite from the Bundelkhand Craton, India: Implication for tectonic and crustal evolution

2020 ◽  
Author(s):  
Mohd Baqar Raza ◽  
Fernando Corfu ◽  
Pritam Nasipuri
Keyword(s):  
High Pressure ◽  
Iron Formation ◽  
Crustal Evolution ◽  
Geochronological Data ◽  
Banded Iron Formation ◽  
Emplacement Temperature ◽  
Eu Anomaly ◽  
Type Granite ◽  
High Silica ◽  
Concordia Diagram

<p>Tonalite-trondhjemite-granodiorite gneisses (TTG) are the oldest litho-units of the Bundelkhand craton. The supracrustal rocks include variable deformed mafic volcanics and Banded Iron Formation. Magmatic zircons from the TTG’s yield an upper intercept of ~ 3590 Ma. The TTG’s gradually grades to a Na-feldspar rich A type porphyric granite towards the south. In this abstract, we report mineralogical, geochemical, and geochronological information of high silica- low Ca - high Na A-type granite from Bundelkhand craton.</p><p>In the TAS diagram, the studied samples plot in the field of granite and have a metaluminous affinity with high Ga/Al and Ce + Y + Nb + Zr values typical of A-type granites. In a primitive normalized multi-element spider diagram, the studied samples exhibit negative Nb, Ti, and P anomalies characteristics of a subduction zone setting. The chondrite normalized REE’s exhibit a strong fractionated pattern with negative Eu anomaly; the LREE are enriched and the HREE depleted with moderate to high (La/Yb)<sub>CN </sub>ratios ranging from 11.12 to 26.24 ppm. The studied samples have plagioclase compositions that vary from X<sub>Ab </sub>= 0.980-0.997 and chlorite compositions varying from X<sub>Mg </sub>= 0.309-0.469.</p><p>Phase equilibria modeling yield an emplacement temperature of 700-750<sup>O</sup>C, at 1.0 GPa. Most of the zircon grains are prismatic with visible cores and rims in optical examinations. In a U-Pb concordia diagram, the grains yield an upper intercept of 2536.6 ± 1.8 Ma. The geochemical and geochronological data taken together, indicate the Na-rich A-type granite generated by the high temperature and high-pressure partial melting of Archaean supracrustal rocks.</p>

scholarly journals The Proterozoic Guanhães banded iron formations, Southeastern border of the São Francisco Craton, Brazil: evidence of detrital contamination

2017 ◽  
Vol 17 (2) ◽  
pp. 303 ◽  
Author(s):  
Vitor Rodrigues Barrote ◽  
Carlos Alberto Rosiere ◽  
Vassily Khoury Rolim ◽  
João Orestes Schneider Santos ◽  
Neal Jesse Mcnaughton
Keyword(s):  
Detrital Zircons ◽  
Iron Formation ◽  
Geochemical Data ◽  
Banded Iron Formations ◽  
Banded Iron Formation ◽  
Zircon Age ◽  
Shallow Marine ◽  
Eu Anomaly ◽  
Depositional Age ◽  
Iron Formations

The Guanhães banded iron formation (BIF) bearing succession occurs as tectonic slices, juxtaposed to Archean TTG granite-gneissic basement rock, developed during the Neoproterozoic-Cambrian Brasiliano collage. The succession has a maximum depositional age of ~2.18 Ga, from detrital zircons in quartzite, and consists of quartzites, schists, BIFs, gneiss and amphibolite, all metamorphosed under amphibolite facies conditions. The Guanhães BIF shows HREE enrichment and consistent positive Eu anomaly (PAAS-normalized REE+Y). Two types of contamination were observed in the samples. The first is contamination by an exotic detrital component, which resulted in low Y/Ho (<30) and Pr/Yb (SN) ratios. Evidence of such contamination, combined with inferred stratigraphic stacking data, indicates that the Guanhães BIFs were deposited on a shallow marine environment. The second type of contamination resulted in higher Eu-anomalies, positive Ce-anomalies, and higher REE+Y concentrations, possibly due to the interaction between later magmatic fluids and the Guanhães BIF. A strong Cambrian event is recorded in zircon age data. The uncontaminated samples display REE+Y distribution similar to other Precambrian BIFs, particularly those from the Morro-Escuro Sequence and the Serra da Serpentina Group, without true Ce-anomalies and Y/Ho close to seawater values (45). Geochronological and geochemical data presented in this paper strongly suggest a correlation between the Guanhães supracrustal succession and the Serra da Serpentina and Serra de São José Groups.

Beginnings of biospheric evolution and their biogeochemical consequences

Paleobiology ◽  
1976 ◽  
Vol 2 (4) ◽  
pp. 351-387 ◽  
Author(s):  
Preston Cloud
Keyword(s):  
Lake Superior ◽  
Large Diameter ◽  
Indirect Evidence ◽  
Iron Formation ◽  
Crustal Evolution ◽  
Confidence Limits ◽  
Sulfate Ion ◽  
Banded Iron Formation ◽  
Simple Diffusion ◽  
Primary Origin

The beginnings of biospheric evolution had far-reaching biogeochemical consequences for the related evolutions of atmosphere, hydrosphere, and lithosphere. Feedback to the sedimentary record from these several simultaneously interacting aspects of crustal evolution provides the evidence from which historical biogeology is reconstructed. The interpretation of that evidence, however, is beset with pitfalls. Both biogenicity and a primary origin need to be demonstrated, or confidence limits established for each supposed morphological and biochemical fossil. Relevance to biospheric or related evolutions must be critically evaluated for every geochemical and sedimentological anomaly.Indirect evidence suggests primitive, oxygen-generating autotrophy by ∼ 3.8 × 109 years ago (3.8 Gyr or gigayears), while free O2 first began to accumulate only ∼ 2 Gyr ago. Various reduced substances in the atmosphere and in solution functioned as oxygen sinks, keeping photolytic and biogenic O2 at levels tolerable by primitive anaerobic and microaerophilic procaryotes.The oldest demonstrably biogenic and certainly primary microstructures are procaryotes from ∼ or > 2 Gyr old strata around Lake Superior. Improved biologic O2 mediation, continued carbon segregation, and filling of O2 sinks initiated atmospheric O2 buildup, leading to an ozone screen ∼ or < 2 Gyr ago. Consequences were essential termination of banded iron formation, onset of red beds, and O2 shielding of anaerobic intracellular processes, heralding the eucaryotic cell.Probable eucaryotes appear in ∼ 1.3 Gyr old rocks in California as large unicells and large-diameter, branched, septate filaments. Likely consequences of eucaryotic evolution were increased atmospheric O2, increased carbonate and sulfate ion, and the rise of sexuality. Meiosis had definitely evolved > 0.7 Gyr ago and probably > 1.3 Gyr ago, perhaps simultaneously with the mitosing cell. Whatever the timing, it completed the evolution of the eucaryotic heredity mechanism and foreshadowed (given sufficient free O2) the differentiation of tissues, organs, and advanced forms of life—with all their potential for biogeochemical feedback to sedimentary, diagenetic, and metallogenic processes. The first Metazoa appeared ∼ 0.7 Gyr ago. Being dependent on simple diffusion for O2, they lacked exoskeletons. The latter appeared, perhaps 0.6 Gyr ago, when increasing O2 levels favored the emergence of more advanced respiratory systems.

TIMS Pb-Pb geochronology of sulfides in the Fazenda Coqueiro VHMS deposit, São Francisco Craton, NE Brazil: timing and genesis constraints on the Zn-Pb mineralization

2020 ◽  
Vol 20 (3) ◽  
pp. 131-152
Author(s):  
Ricardo Ramos Spreafico ◽  
Johildo Salomão Figueiredo Barbosa ◽  
Moacir José Buenano Macambira ◽  
Marco Antônio Galarza
Keyword(s):  
Massive Sulfide ◽  
Ocean Floor ◽  
Iron Formation ◽  
Upper Crust ◽  
Geochronological Data ◽  
Banded Iron Formation ◽  
Tectonic Event ◽  
Mineralization Age ◽  
Siliciclastic Rocks

TIMS Pb-Pb geochronological data allow determination of the timing and genesis of the Fazenda Coqueiro volcanic‑hosted massive sulfide (VHMS) Zn-Pb deposit hosted in the Neoarchean Mundo Novo greenstone belt (MNGB), NE São Francisco Craton. The deposit is inserted in the Rhyacian-Orosirian Contendas-Jacobina lineament between Archean cratonic blocks. The basement of the deposit is composed of Paleoarchean metagranite and metarhyolite nuclei tectonically emplaced within the supracrustal rocks. The volcanic-sedimentary rocks comprise the ocean floor western metabasalt, calcsilicate rock, aluminous schist, metachert, banded iron formation, and tremolitite of the middle sequence and metasedimentary siliciclastic rocks of the uppermost sequence of the MNGB. The western metabasalt is hydrothermally altered, which resulted in the formation of two alteration zones. They consist of carbonate zone, proximal, hosting massive sulfides composed mainly of sphalerite and galena with minor chalcopyrite; and sericite-chlorite zone, distal, hosting mainly disseminated chalcopyrite. Pb-Pb galena, chalcopyrite and sphalerite data from the massive and disseminated zones in the Fazenda Coqueiro deposit yielded model ages of 2,804 ± 11.15, 2,794 ± 11.2, and 2,767 ± 11.1 Ma, respectively, with the Pb sourced from the upper crust, based on the uranogenic and thorogenic diagrams. The Pb-Pb isochron mineralization age of 2,747 ± 16 Ma obtained from chalcopyrite and sphalerite samples from the massive and disseminated zones suggests that the sulfides were coeval and do not record later metamorphic-hydrothermal events. Therefore, the Fazenda Coqueiro deposit would have formed from Neoarchean ocean floor volcanic-exhalative processes. The Rhyacian-Orosirian tectonic event compressed the deposit between Archean blocks along the Contendas-Jacobina lineament, preserving the sulfides from remobilization processes.

Earth’s Middle Ages: What Came after the GOE

2017 ◽  
Author(s):  
Donald Eugene Canfield
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Middle Ages ◽  
Atmospheric Oxygen ◽  
Iron Formation ◽  
Banded Iron Formation ◽  
Dissolved Iron ◽  
Great Oxidation Event ◽  
Low Levels ◽  
Substantial Rise

This chapter considers the aftermath of the great oxidation event (GOE). It suggests that there was a substantial rise in oxygen defining the GOE, which may, in turn have led to the Lomagundi isotope excursion, which was associated with high rates of organic matter burial and perhaps even higher concentrations of oxygen. This excursion was soon followed by a crash in oxygen to very low levels and a return to banded iron formation deposition. When the massive amounts of organic carbon buried during the excursion were brought into the weathering environment, they would have represented a huge oxygen sink, drawing down levels of atmospheric oxygen. There appeared to be a veritable seesaw in oxygen concentrations, apparently triggered initially by the GOE. The GOE did not produce enough oxygen to oxygenate the oceans. Dissolved iron was removed from the oceans not by reaction with oxygen but rather by reaction with sulfide. Thus, the deep oceans remained anoxic and became rich in sulfide, instead of becoming well oxygenated.

A new volcanic province: evidence from glacial erratics in western North Greenland

2000 ◽  
pp. 35-41 ◽  
Author(s):  
Peter R. Dawes ◽  
Bjørn Thomassen ◽  
T.I. Hauge Andersson
Keyword(s):  
Volcanic Rocks ◽  
Iron Formation ◽  
Banded Iron Formation ◽  
Common Component ◽  
Volcanic Province ◽  
North West ◽  
North East ◽  
The North ◽  
Surficial Deposits ◽  
North Greenland

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Dawes, P. R., Thomassen, B., & Andersson, T. H. (2000). A new volcanic province: evidence from glacial erratics in western North Greenland. Geology of Greenland Survey Bulletin, 186, 35-41. https://doi.org/10.34194/ggub.v186.5213 _______________ Mapping and regional geological studies in northern Greenland were carried out during the project Kane Basin 1999 (see Dawes et al. 2000, this volume). During ore geological studies in Washington Land by one of us (B.T.), finds of erratics of banded iron formation (BIF) directed special attention to the till, glaciofluvial and fluvial sediments. This led to the discovery that in certain parts of Daugaard-Jensen Land and Washington Land volcanic rocks form a common component of the surficial deposits, with particularly colourful, red porphyries catching the eye. The presence of BIF is interesting but not altogether unexpected since BIF erratics have been reported from southern Hall Land just to the north-east (Kelly & Bennike 1992) and such rocks crop out in the Precambrian shield of North-West Greenland to the south (Fig. 1; Dawes 1991). On the other hand, the presence of volcanic erratics was unexpected and stimulated the work reported on here.

scholarly journals Serpentine–Hisingerite Solid Solution in Altered Ferroan Peridotite and Olivine Gabbro

Minerals ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 47 ◽  
Author(s):  
Benjamin Tutolo ◽  
Bernard Evans ◽  
Scott Kuehner
Keyword(s):  
Iron Formation ◽  
Olivine Gabbro ◽  
Banded Iron Formation ◽  
Silicate System ◽  
Duluth Complex ◽  
Sheet Silicate ◽  
Structure Modulation ◽  
Compositional Variability ◽  
Common Observation ◽  
End Members

We present microanalyses of secondary phyllosilicates in altered ferroan metaperidotite, containing approximately equal amounts of end-members serpentine ((Mg,Fe2+)3Si2O5(OH)4) and hisingerite (□Fe3+2Si2O5(OH)4·nH2O). These analyses suggest that all intermediate compositions can exist stably, a proposal that was heretofore impossible because phyllosilicate with the compositions reported here have not been previously observed. In samples from the Duluth Complex (Minnesota, USA) containing igneous olivine Fa36–44, a continuous range in phyllosilicate compositions is associated with hydrothermal Mg extraction from the system and consequent relative enrichments in Fe2+, Fe3+ (hisingerite), Si, and Mn. Altered ferroan–olivine-bearing samples from the Laramie Complex (Wyoming, USA) show a compositional variability of secondary FeMg–phyllosilicate (e.g., Mg–hisingerite) that is discontinuous and likely the result of differing igneous olivine compositions and local equilibration during alteration. Together, these examples demonstrate that the products of serpentinization of ferroan peridotite include phyllosilicate with iron contents proportionally larger than the reactant olivine, in contrast to the common observation of Mg-enriched serpentine in “traditional” alpine and seafloor serpentinites. To augment and contextualize our analyses, we additionally compiled greenalite and hisingerite analyses from the literature. These data show that greenalite in metamorphosed banded iron formation contains progressively more octahedral-site vacancies (larger apfu of Si) in higher XFe samples, a consequence of both increased hisingerite substitution and structure modulation (sheet inversions). Some high-Si greenalite remains ferroan and seems to be a structural analogue of the highly modulated sheet silicate caryopilite. Using a thermodynamic model of hydrothermal alteration in the Fe–silicate system, we show that the formation of secondary hydrothermal olivine and serpentine–hisingerite solid solutions after primary olivine may be attributed to appropriate values of thermodynamic parameters such as elevated a S i O 2 ( a q ) and decreased a H 2 ( a q ) at low temperatures (~200 °C). Importantly, recent observations of Martian rocks have indicated that they are evolved magmatically like the ferroan peridotites analyzed here, which, in turn, suggests that the processes and phyllosilicate assemblages recorded here are more directly relevant to those occurring on Mars than are traditional terrestrial serpentinites.

Cobalt-Bearing Grunerite in the Metamorphosed Banded Iron Formation in Orissa, India

2011 ◽  
Vol 61 (3) ◽  
pp. 281-289 ◽  
Author(s):  
Prasanta Kumar NAYAK ◽  
Birendra Kumar MOHAPATRA ◽  
Prem Prakash SINGH ◽  
Ranjit Kumar MARTHA
Keyword(s):  
Iron Formation ◽  
Banded Iron Formation
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