Mechanisms of Archean crust formation inferred from high-precision HFSE systematics in TTGs

2011 ◽  
Vol 75 (15) ◽  
pp. 4157-4178 ◽  
Author(s):  
J. Elis Hoffmann ◽  
Carsten Münker ◽  
Tomas Næraa ◽  
Minik T. Rosing ◽  
Daniel Herwartz ◽  
...  
Keyword(s):  
High Precision ◽  
Crust Formation ◽  
Archean Crust

Nd evidence for extensive Archean basement in the western Churchill Province, Canada

1986 ◽  
Vol 23 (9) ◽  
pp. 1433-1437 ◽  
Author(s):  
C. D. Frost ◽  
R. A. Burwash
Keyword(s):  
Drill Hole ◽  
Crust Formation ◽  
Southern Alberta ◽  
Northern Saskatchewan ◽  
Archean Crust ◽  
Northeastern Alberta ◽  
Archean Basement

To determine the extent of reworked Archean crust in the western Churchill Province, we have examined Sm–Nd crustal residence ages of basement cores in southern Alberta and southwestern Saskatchewan along with crustal residence ages calculated for other Sm–Nd data available from the Churchill Province. The deep drill hole samples from the Interior Platform give Sm–Nd crustal residence ages that average 2.8 Ga. Granulites from northeastern Alberta and composite gneisses from northern Saskatchewan also provide Archean crustal residence ages. These data demonstrate that the presence of reworked Archean crust in the western Churchill Province is more widespread than has been confirmed previously. We suggest that Sm–Nd crustal residence ages are valuable estimates of crust formation times, especially in orogenic areas where other isotope systems have been disturbed.

Constraints on Archean crust formation from open system models of Earth evolution

2019 ◽  
Vol 530 ◽  
pp. 119307 ◽  
Author(s):  
Seema Kumari ◽  
Debajyoti Paul ◽  
Andreas Stracke
Keyword(s):  
Open System ◽  
Crust Formation ◽  
System Models ◽  
Archean Crust

scholarly journals Relationship between magmatic, metamorphic and hydrothermal processes within the Baikal-Muya terrane (Eastern Siberia): constraints from a high-precision geochronological study of the Kedrovsky granitoid massif

2019 ◽  
Vol 489 (3) ◽  
pp. 292-297
Author(s):  
A. V. Chugaev ◽  
I. V. Chernyshev ◽  
E. Y. Rytsk ◽  
E. B. Salnikova ◽  
A. A. Nosova ◽  
...  
Keyword(s):  
Continental Crust ◽  
High Precision ◽  
Gold Mineralization ◽  
Early Stage ◽  
Eastern Siberia ◽  
Crust Formation ◽  
Metasedimentary Rocks ◽  
Geochronological Study ◽  
Granitoid Massif ◽  
Proterozoic Continental Crust

High-precision dating of granitoids is significant for identification the ages of the main stages of crust formation in various blocks of the continental crust. In this work, we dating the Kedrovskiy diorite-granodiorite massif localized within the South Muya block of the Baikal-Muya accretion terrane (BMT) (Eastern Siberia) among the Neoproterozoic gabbroids of the Kedrovskiy complex and metasedimentary rocks of the Kedrovskaya Formation. The results of U-Pb (ID TIMS) and 39Ar-40Ar geochronological studies of the Kedrovskiy massif are discussed. The formation of the massif (781 3 Ma) occurred at an early stage formation of the Proterozoic continental crust of BMT during accretion of Baikalids with the Siberian craton. A later thermal event (626 11 Ma) of the Ediacaran stage evolution BMT is reflected in the formation of of biotite-quartz-feldspar veins that cut through the granitoids of the Kedrovka massif. The obtained geochronological data show that the gold mineralization of the Kedrovskiy deposit (273 4 Ma) was not generated by the Kedrovskiy massif granitoids.

Geochemistry of xenolithic eclogites from West Africa, part I: A link between low MgO eclogites and archean crust formation

2001 ◽  
Vol 65 (9) ◽  
pp. 1499-1527 ◽  
Author(s):  
Matthias G. Barth ◽  
Roberta L. Rudnick ◽  
Ingo Horn ◽  
William F. McDonough ◽  
Michael J. Spicuzza ◽  
...  
Keyword(s):  
West Africa ◽  
Crust Formation ◽  
Archean Crust

Automatic measurement of SAED patterns from asbestos minerals

1988 ◽  
Vol 46 ◽  
pp. 846-847
Author(s):  
J. C. Russ ◽  
T. Taguchi ◽  
P. M. Peters ◽  
E. Chatfield ◽  
J. C. Russ ◽  
...  
Keyword(s):  
Diffraction Pattern ◽  
High Precision ◽  
Diffraction Data ◽  
Automatic Measurement ◽  
Automatic Method ◽  
Important Method ◽  
X Ray ◽  
Integrated Intensity ◽  
Asbestiform Minerals ◽  
True Center

Conventional SAD patterns as obtained in the TEM present difficulties for identification of materials such as asbestiform minerals, although diffraction data is considered to be an important method for making this purpose. The preferred orientation of the fibers and the spotty patterns that are obtained do not readily lend themselves to measurement of the integrated intensity values for each d-spacing, and even the d-spacings may be hard to determine precisely because the true center location for the broken rings requires estimation. We have implemented an automatic method for diffraction pattern measurement to overcome these problems. It automatically locates the center of patterns with high precision, measures the radius of each ring of spots in the pattern, and integrates the density of spots in that ring. The resulting spectrum of intensity vs. radius is then used just as a conventional X-ray diffractometer scan would be, to locate peaks and produce a list of d,I values suitable for search/match comparison to known or expected phases.

On effects of non-systematic reflections on weak-beam images of partial dislocations

1991 ◽  
Vol 49 ◽  
pp. 688-689
Author(s):  
K. Z. Botros ◽  
S. S. Sheinin
Keyword(s):  
High Precision ◽  
Stacking Fault ◽  
Important Application ◽  
Stacking Fault Energy ◽  
Sharp Peak ◽  
Weak Beam ◽  
Partial Dislocations ◽  
Deviation Parameter ◽  
Beam Diffraction

The main features of weak beam images of dislocations were first described by Cockayne et al. using calculations of intensity profiles based on the kinematical and two beam dynamical theories. The feature of weak beam images which is of particular interest in this investigation is that intensity profiles exhibit a sharp peak located at a position very close to the position of the dislocation in the crystal. This property of weak beam images of dislocations has an important application in the determination of stacking fault energy of crystals. This can easily be done since the separation of the partial dislocations bounding a stacking fault ribbon can be measured with high precision, assuming of course that the weak beam relationship between the positions of the image and the dislocation is valid. In order to carry out measurements such as these in practice the specimen must be tilted to "good" weak beam diffraction conditions, which implies utilizing high values of the deviation parameter Sg.

Digital differential hysteresis iimage processing displays what the microscope acquires but the eye can't see

1995 ◽  
Vol 53 ◽  
pp. 642-643
Author(s):  
Klaus-Ruediger Peters
Keyword(s):  
Image Processing ◽  
Visual System ◽  
High Precision ◽  
Image Data ◽  
Processing Technology ◽  
Output Data ◽  
Contrast Resolution ◽  
Pixel Intensity ◽  
Data Reading ◽  
Hysteresis Properties

Differential hysteresis processing is a new image processing technology that provides a tool for the display of image data information at any level of differential contrast resolution. This includes the maximum contrast resolution of the acquisition system which may be 1,000-times higher than that of the visual system (16 bit versus 6 bit). All microscopes acquire high precision contrasts at a level of <0.01-25% of the acquisition range in 16-bit - 8-bit data, but these contrasts are mostly invisible or only partially visible even in conventionally enhanced images. The processing principle of the differential hysteresis tool is based on hysteresis properties of intensity variations within an image.Differential hysteresis image processing moves a cursor of selected intensity range (hysteresis range) along lines through the image data reading each successive pixel intensity. The midpoint of the cursor provides the output data. If the intensity value of the following pixel falls outside of the actual cursor endpoint values, then the cursor follows the data either with its top or with its bottom, but if the pixels' intensity value falls within the cursor range, then the cursor maintains its intensity value.

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