STRUCTURAL GEOLOGY OF PRECAMBRIAN ROCKS SOUTH OF BANCROFT, ONTARIO

1966 ◽  
Vol 3 (4) ◽  
pp. 441-455 ◽  
Author(s):  
Myron G. Best
Keyword(s):  
Structural Geology ◽  
Structural Analysis ◽  
Rock Type ◽  
Structural Characteristics ◽  
Metamorphic Rocks ◽  
Grenville Province ◽  
Precambrian Rocks ◽  
Working Hypothesis ◽  
Tectonic History ◽  
Structural Character

Structural analysis of Precambrian metamorphic rocks south of Bancroft, Ontario, has disclosed fold structures in lithologic layering, which are examined on the working hypothesis that two distinct generations are present. Folds of the first system, in the southern part of the mapped area, are fairly open, nearly recumbent, and plunge gently eastward, whereas folds of the second system, found in the northern part of the area, are tighter, with steep southeast-dipping axial planes and variably oriented axes. Uniformly steep stratiform foliation and linear mineral segregations, characterizing an extensive terrain between the so-called Hastings basin and the Haliburton–Hastings highlands, seem to have evolved by progressive tightening of the second folds and transposition of the layering parallel to the axial planes. In the area studied, the distinction between the highlands and the basin is basically one of predominant rock type, with progressive changes in structural character evident between the two. As formerly reported, the distinction involved strongly contrasting structural characteristics, with intervening zones of faulting.This part of the Grenville province is structurally very complex, and considerably more data and analysis are needed to unravel the tectonic history.

Lithoprobe line 55: integration of out-of-plane seismic results with surface structure, metamorphism, and geochronology, and the tectonic evolution of the eastern Grenville Province

2000 ◽  
Vol 37 (2-3) ◽  
pp. 341-358 ◽  
Author(s):  
Andrew Hynes ◽  
Aphrodite Indares ◽  
Toby Rivers ◽  
André Gobeil
Keyword(s):  
High Pressure ◽  
Three Dimensional ◽  
Good Control ◽  
Crustal Thickening ◽  
Metamorphic Rocks ◽  
Seismic Line ◽  
Grenville Province ◽  
Tectonic Model ◽  
Tectonic History ◽  
Out Of Plane

Lithoprobe line 55, in the Grenville Province of eastern Quebec, provides unusually good control on the three-dimensional (3-D) geometry and structural relationships among the major lithological units there. Archean basement underlies the exposed Proterozoic rocks, along the entire seismic line, and there is a lateral ramp in this basement immediately behind a lobate stack of thrust slices of high-pressure metamorphic rocks comprising the Manicouagan Imbricate Zone (MIZ). Integration of the 3-D geometry with P-T and geochronological data allows derivation of a tectonic model for the region. The MIZ was buried to depths >60 km at 1050 Ma. Preservation of its high-pressure assemblages, and the absence of metamorphism at 990 Ma, which is characteristic of lower pressure metamorphic rocks that tectonically overlie them, indicates the MIZ rocks were rapidly unroofed, early in the tectonic history. There were two discrete pulses of crustal thickening during the Grenvillian Orogeny in this region. The first, involving imbrication of Labradorian and Pinwarian rocks that comprised part of southeast Laurentia, culminated in the Ottawan pulse at ca. 1050 Ma, and produced the high-pressure metamorphism of the MIZ. Its effects were rapidly reversed, with extrusion of the MIZ rocks to shallow crustal levels at ca. 1020 Ma. The crust was again thickened, with the Moho subsiding to depths >60 km, in the Rigolet pulse at ca. 990 Ma. The site of extrusion of the MIZ was probably controlled by the subsurface lateral ramp. High geothermal gradients indicate that extrusion may have been aided by lithospheric delamination in the crustal-thickening zone.

XXII.—The Petrology of Picritic Rocks in Minor Intrusions—a Hebridean Group

1959 ◽  
Vol 63 (3) ◽  
pp. 459-499 ◽  
Author(s):  
H. I. Drever ◽  
R. Johnston
Keyword(s):  
Source Rock ◽  
Rock Type ◽  
Basaltic Magma ◽  
Ultrabasic Rock ◽  
Working Hypothesis ◽  
Selective Fusion ◽  
Rich Liquid ◽  
Factual Data

SynopsisThe results are presented of a detailed petrological reconnaissance of a group of picritic minor intrusions in the Hebrides. A substantial amount of new factual data is subjected to a unified treatment as a basis for reference and discussion. Olivine phenocrysts are not appreciably zoned and there is no evidence that they have a reaction relation with the liquid represented by the groundmass. Variations in the size and amount of olivine in individual intrusions are examined in detail and attributed to composite intrusion of differentiated material. A distinctive non-porphyritic facies found in several sills and in one dyke is chemically analyzed. Four analyses from widely separated localities establish this facies as a remarkably invariant, eucritic rock-type. The composition of the groundmass of the picritic rocks is variable and there is no evidence whatever of the participation of basaltic magma in their formation. Although no attempt is made to explain the new data in detail, a comprehensive working hypothesis is formulated. The origin of such picritic intrusions is believed to be due to selective fusion of pre-existing ultrabasic rock. Liquid more basic than normal basalt magmas can be formed by this process. Some re-precipitation of olivine may have preceded final emplacement of a magnesia-rich liquid which contained xenocrysts, mainly of olivine, from the source rock.

Gasparite-(La), La(AsO4), a new mineral from Mn ores of the Ushkatyn-III deposit, Central Kazakhstan, and metamorphic rocks of the Wanni glacier, Switzerland

2019 ◽  
Vol 104 (10) ◽  
pp. 1469-1480 ◽  
Author(s):  
Oleg S. Vereshchagin ◽  
Sergey N. Britvin ◽  
Elena N. Perova ◽  
Aleksey I. Brusnitsyn ◽  
Yury S. Polekhovsky ◽  
...  
Keyword(s):  
Structural Characteristics ◽  
Type Specimen ◽  
Type Locality ◽  
Metamorphic Rocks ◽  
New Mineral ◽  
Chemical Compositions ◽  
Holotype Specimen ◽  
Rare Earth Minerals ◽  
Formation Conditions ◽  
Different Origins

Abstract Gasparite-(La), La(AsO4), is a new mineral (IMA 2018-079) from Mn ores of the Ushkatyn-III deposit, Central Kazakhstan (type locality) and from alpine fissures in metamorphic rocks of the Wanni glacier, Binn Valley, Switzerland (co-type locality). Gasparite-(La) is named for its dominant lanthanide, according to current nomenclature of rare-earth minerals. The occurrences and parageneses in both localities are distinct: minute isometric grains up to 15 μm in size, associated with friedelite, jacobsite, pennantite, manganhumite series minerals (alleghanyite, sonolite), sarkinite, tilasite, and retzian-(La) are typically embedded into calcite-rhodochrosite veinlets (Ushkatyn-III deposit) vs. elongated crystals up to 2 mm in size in classical alpine fissures in two-mica gneiss without indicative associated minerals (Wanni glacier). Their chemical compositions have been studied by EDX and WDX; crystal-chemical formulas of gasparite-(La) from the Ushkatyn-III deposit (holotype specimen) and Wanni glacier (co-type specimen) are (La0.65Ce0.17Nd0.07Ca0.06Mn0.05Pr0.02)1.02[(As0.70V0.28P0.02)1.00O4] and (La0.59Ce0.37Nd0.02 Ca0.02Th0.01)1.01[(As0.81P0.16Si0.02S0.02)1.01O4], respectively. In polished sections, crystals are yellow and translucent with bright submetallic luster. Selected reflectance values R1/R2 (λ, nm) for the holotype specimen in air are: 11.19/9.05 (400), 11.45/9.44 (500), 10.85/8.81 (600), 11.23/9.08 (700). The structural characteristics of gasparite-(La) were studied by means of EBSD (holotype specimen), XRD, and SREF (co-type specimen). Gasparite-(La) has a monoclinic structure with the space group P21/n. Our studies revealed that gasparite-(La) from the Ushkatyn-III deposit and Wanni glacier have different origins. La/Ce and As/P/V ratios in gasparite-(La) may be used as an indicator of formation conditions.

scholarly journals Whole rock major element influences on monazite growth: examples from igneous and metamorphic rocks in the Menderes Massif, western Turkey

Mineralogia ◽  
2008 ◽  
Vol 39 (1-2) ◽  
pp. 7-30 ◽  
Author(s):  
Elizabeth Catlos ◽  
Courteney Baker ◽  
Ibrahim Çemen ◽  
Cenk Ozerdem
Keyword(s):  
Major Element ◽  
Bulk Composition ◽  
Metamorphic Rocks ◽  
Western Turkey ◽  
Menderes Massif ◽  
Tectonic History ◽  
Major Element Chemistry ◽  
Element Chemistry ◽  
Multi Stage ◽  
Mineral Assemblages

Whole rock major element influences on monazite growth: examples from igneous and metamorphic rocks in the Menderes Massif, western TurkeyMonazite (LREEPO4) is a radiogenic, rare-earth bearing mineral commonly used for geochronology. Here we examine the control of major element chemistry in influencing the crystallization of monazite in granites (Salihli and Turgutlu bodies) and garnet-bearing metamorphic assemblages (Bozdag and Bayindir nappes) from the Menderes Massif, western Turkey. In S-type granites from the massif, the presence of monazite correlates to the CaO and Al2O3content of the whole rock. Granites with monazite only are low Ca (0.6-1.8 wt% CaO). As CaO increases (from 2.1-4.6 wt%), allanite [(Ce, Ca, Y)2(Al, Fe3+)3(SiO4)3(OH)] is present. Higher Al2O3(>15 wt%) rocks contain allanite and/or monazite, whereas those with lower Al2O3contain monazite only. However, examining data reported elsewhere for A-type granites, the correlation between major element chemistry and presence of monazite is likely restricted to S-type lithologies. Pelitic schists of the Menderes Massif show no correlation between major element chemistry and presence of monazite. One Bayindir nappe sample contains both prograde garnets and those affected significantly by diffusion. These rocks have likely experienced a complicated multi-stage tectonic history, which influenced their current mineral assemblages. The presence of monazite in a metamorphic rock can be influenced by the number, duration, and nature of events that were experienced and the degree to which fluids were involved. The source of monazite in the Bayindir and Bozdag samples was likely reactions that involved allanite. These reactions may not have significantly changed the bulk composition of the rock.

A model for the origin of the Lac St. Jean anorthosite massif

1976 ◽  
Vol 13 (2) ◽  
pp. 389-399 ◽  
Author(s):  
R. A. Frith ◽  
K. L. Currie
Keyword(s):  
Experimental Data ◽  
Partial Melting ◽  
Metamorphic Rocks ◽  
High Grade ◽  
Calc Alkaline ◽  
Grenville Province ◽  
Thermal Event ◽  
Anorthosite Massif ◽  
Mineral Assemblages ◽  
Potassic Rocks

An ancient tonalitic complex becomes migmatitic around the Lac St. Jean massif, ultimately losing its identity in the high grade metamorphic rocks surrounding the anorthosite. Field relations suggest extreme metamorphism and anatexis of tonalitic rocks. Experimental data show that extensive partial melting of the tonalite leaves an anorthositic residue. The same process operating on more potassic rocks would leave monzonitic or quartz syenitic residues. Synthesis of experimental data suggests that the process could operate at pressures of 5–8 kbar and temperatures of 800–1000 °C, which are compatible with mineral assemblages around the anorthosite massif. Slightly higher temperatures at the end of the process could generate magmatic anorthosite.Application of the model to the Grenville province as a whole predicts generation of anorthosite during a long-lived thermal event of unusual intensity. Residual anorthosite would occur as a substratum in the crust, overlain by high-grade metamorphic rocks intruded by anorthosite and syenitic rocks, while higher levels in the crust would display abundant calc-alkaline plutons and extrusives.

An application of Nd isotope mapping in structural geology: delineating an allochthonous Grenvillian terrane at North Bay, Ontario

2003 ◽  
Vol 140 (5) ◽  
pp. 539-548 ◽  
Author(s):  
A. P. DICKIN ◽  
R. H. MCNUTT
Keyword(s):  
Structural Geology ◽  
Amphibolite Facies ◽  
High Grade ◽  
Grenville Province ◽  
Nd Isotope ◽  
Bay Area ◽  
The North ◽  
Depleted Mantle ◽  
Different Types ◽  
Isotope Analyses

Fifty new Nd isotope analyses are presented from the North Bay area of the Grenville Province in Ontario. These data are used to map the extent of an allochthonous Grenvillian terrane which is an outlier of the Allochthonous Polycyclic Belt of the Grenville Province. Amphibolite facies orthogneisses from the allochthonous terrane have depleted mantle Nd model ages (TDM) below 1.8 Ga, whereas the gneisses of the structurally underlying parautochthon almost invariably have model ages above 1.8 Ga. The distribution of model ages is consistent with the distribution of distinct types of metabasic rock, used by other researchers as the criterion for recognizing rocks of the allochthonous and parautochthonous belts of the Grenville Province. The agreement between these different types of evidence demonstrates that Nd isotope mapping is a reliable and powerful tool for mapping terrane boundaries in high-grade metamorphic belts.

scholarly journals Structural Symmetry of DNA Nucleotides and Steroid Hormones

2020 ◽  
Author(s):  
Charles Schaper
Keyword(s):  
Structural Analysis ◽  
Steroid Hormones ◽  
Functional Group ◽  
Structural Characteristics ◽  
Base Pairs ◽  
Detailed Structural Analysis ◽  
Structural Association ◽  
Direct Binding ◽  
Structural Correspondence ◽  
Oxygen Group

DNA is comprised of important structural characteristics, which include the complementary base pairs of adenine-thymine (A-T) and cytosine-guanine (C-G) that serve to initiate and code for transcription and translation into amino acids. Recently, structural analysis of DNA performed in this lab indicated that each DNA nucleotide complementary base pair is in perfect correspondence with the structure of the steroid molecule and steroid hormones. Here, detailed structural analysis and illustrations are presented to clearly support and extend this fundamental finding. The structural illustrations indicate that the DNA Nucleotide base pairs can achieve perfect alignment with steroid hormones, such that each of its functional groups can be assigned a purpose for binding, stabilization, and transcription regulation. The relation of the missing third hydrogen bond for A-T and T-A, relative to the three hydrogen bonds of C-G and G-C, is clearly shown to be found through its coupling with the class of corticosteroids like cortisol that have an oxygen group perfectly positioned for interaction with the available functional group of thymine. Thus the intermolecular coupling by hydrogen bonding of Cortisol-Thymine produces a strong complex. Moreover, the structural analysis of the end group couplings to an ionic linkage element, Ca2+ or Mg2+, demonstrate interaction with both the DNA phosphates as well as the oxygen element within the sugar. The relationships confirm a structural association of cortisol-like steroid hormones with A-T and T-A and a structural association of testosterone-like steroid hormones for G-C and C-G. Synthetic steroids are assessed, including prednisolone and dexamethasone, to indicate consistency of the functional group interactions with the DNA base pairs, phosphate, and sugar groups to support and confirm direct binding and structural correspondence of steroid hormones to DNA Nucleotides.

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