Polyphase Deformation

Rapur area forms southern part of the Nellore schist belt of Andhra Pradesh. The area under study located between latitude 14 o 15' 00" and 14 o 11' 30" and longitude 79 o 32' 55" and 79 o 37' 30"and covers an area about 30 Km 2 . The dominant rock types exposed in the area are Metabasalt, Quartz Mica Schist, Quartzite belonging to Nellore Schist Belt (NSB), undifferentiated granitoids of PGC II and younger acidic and basic intrusives. These granitoids are sandwiched between NSB and Nallamalai Fold Belt (NFB) rocks, which are exposed along eastern and western side of the mapped area. The unclassified granitoids of the area has been mapped and classified on the basis of their modal percentage, mineralogical and geochemical characteristics, which are grouped into two suites: 1. Tonalite-Granodiorite-Monzonite suites (TGM) 2. Monzonite-Syenite suite (MS). Rapur area predominated by TGM suite of rocks, which includes mainly Hornblende Biotite Gneiss and Orbicular Granite. Hornblende Biotite Gneiss are tonalitic to granodioritic in composition. The gneissosity is defined by parallel alignment of mafic and felsic minerals in the Hornblende Biotite Gneiss. Gneissosity plane is parallel to the schistosity of metabasalt of NSB trending NW-SE direction defining the regional foliation in the area. The orbicular granite, a variant of Hornblende Biotite Gneiss, contains oval to orb-shaped phenocryst of plagioclase and k-feldspar set within fine grained matrix of quartz, feldspars, biotite and hornblende. The MS suites of rock consist of alkali feldspar granite and monzogranite, which are exposed near Marlapudi and NE of Rapur. The alkali feldspar granite intruded along NS trending plane, while Monzogranite intruded along NE trending axial plane of regional F3 fold.The area suffered a polyphase deformation. The first phase of deformation produced isoclinal (F1) folds with the development of pervassive schistosity (S1). These have been involved in coaxial upright (F2) folding with the axial plane striking NW'ly, with the development of crenulation cleavage (S2) at places. The last phase of deformation produced (F3) folds with three sets of vertical axial planes striking N330, N75 and N285.

Pulse compression technique is most widely used in radar and communication areas. Its implementation requires an optimized and dedicated hardware. The real time implementation places several constraints such as area occupied, power consumption , etc. The good design needs optimization of these constraints. This paper concentrates on the design of optimized model which can reduce these. In the proposed architecture a single chip is used for generating the pulse compression sequence like BPSk, QPSk, 6-PSK and other Polyphase codes. The VLSI architecture is implemented on the Field Programm-able Gate Array (FPGA) as it provides the flexibility of reconfigurability and reprogrammability .It was found that the proposed architecture has generated the pulse compression sequences efficiently while improving some of the parameters like area, power consumption and delay when compared to previous methods.

The Meso- to Neo-proterozoic Delhi Fold Belt (DFB) forms the backbone of Aravalli mountain range  which flanks the western edge of Indian shield. The DFB is delimited in the east by the Banded Gneissic Complex (BGC), Aravalli Fold Belt near Gogunda and the Vindhyan Supergroup, in the west by the pockets of BGC, Erinpura Granite (towards the South-West) and vast expanse of Phanerozoic and Alluvium elements along the Phulad Shear Zone which is also referred as Western Margin Fault in some other literature.
As far as the structural interpretation of the DFB is concerned, co-axial deformation and type 3 interference pattern are the two dominant phases described by Roday (1979), Naha (1984) and others. They described two types of major folding pattern: first isoclinal, recumbent folds and after that upright, open folds. According to them there is a large synclinorium in DFB but they mostly worked on the North Delhi Fold Belt (NDFB). Based on the fold vergence a flower structure is indicated instead of a synclinorium in the South Delhi Fold Belt (SDFB) by Sugden, (1987, p 138), where the faults splay upwards. Although a lot of work is done on the NDFB but little work is done in the SDFB which is also very unclear to understand the tectono-  stratigraphy of the mobile belt. So, the present study covers the study of the two part of the eastern boundary of the Ranakpur Shear Zone (RSZ). The Parashuramji is situated in the east just adjacent to RSZ. Kumbhalgarh is in the northeast of Parashuramji.
In the present study, it covers almost 215 sq. Km area along two transects between Kelwara to Sadri (East to West) and from Parashuramji Mahadev cave to Sayra (North to South) respectively. The rocks of the area are almost NNE-SSE trending The major difference between and the foliation planes dip towards west in Kumbhalgarh area whereas the foliations of Parashuramji dip towards east direction. Stereonet plotting shows that the fold axis of the major fold plunges around 100 southerly. Z- and S- shaped folds are also found within the foliation planes in several places as well as M-shaped folds in outcrop scale. So, a large synclinorium structure can thus be assumed. Within the foliation, boudins are found which are also folded . It thus supports polyphase deformation events in this region which occurs as follows: An initial extensional event where boudins are formed, followed by an compression when the boudins are folded. The isoclinal, upright folds plunge around 300 towards south, so E-W compressional events of several phases may be considered for the development of tight isoclinal folds of SDFB. Hook shaped fold  (type 3 of Ramsay and Huber) are also observed in Kumbhalgarh fort area.
The effects of the shear zone are present in Parashuramji, the central part of the area. some meso-scopic structures like rotation of foliation and  asymmetry of intrafolial fold are found in the area. Sheath folds are also found in the southern part of Parashuramji. The orientation of the axial planes of the folds are NNE-SSW/600 towards East. Teardrop shape folds are also found here.

      The rocks of the DFB are mostly of a metasedimentary origin and comprise gneisses and schists with very minor occurrences of quartzite, granite, pegmatite, diorite and amphibolite which indicate a metamorphic terrain multiply intruded by the igneous bodies of varying origin. Several microstructures are identified in the thin section of the rocks. Presence of σ-structure and C-S structure indicate the evidence of shearing. Low  (300-4000C) to medium (400-5000C) temperature metamorphism is interpreted from the microstructural study of the rocks. Bulging (BLG) recrystallisation is the one of the evidence of low temperature grain boundary migration. Undulose extinction and deformation lamellae are the other evidences of low grade metamorphism of the rocks.

Recrystallised quartz in a fabric with alternating quartz and feldspar layers is evident of medium temperature metamorphism. Here grain size of quartz depends upon the width of the quartz layer. Perthite with flame shaped albite lamellae (Ab) and tapered deformation twining of feldspar (type II) as well as greenschist (albite + epidote + quartz) to amphibolite facies (hornblende + plagioclase + garnet) mineral assemblage support the medium grade metamorphism of the rocks.

The rocks of this area is generally NNE-SSW trending but the major difference between the nearby two area is the dip direction of foliation planes. In the eastern part, near Kumbhalgarh fort, foliation planes dip towards west whereas foliations of Parashuramji cave area dip towards east. In detail study of the both part it is noticed in many places that there are Z- and S- shaped folds present in the eastern part and western part respectively. The plunge of the fold axes are nearly 18 towards 180.So, in the large scale it can be assumed that there is a large synclinorium. M-shaped folds are present within an almost 50m outcrop. The folds also plunges 15 degree towards 190 degree. Shear zones signatures like asymmetric folds, rotation of boudins and sheath folds are observed. Three phases of deformation are interpreted clearly in the mapped area. First, an early extension was followed by compression and formation of isoclinal, tight folding are observed. Therefore the boudins are folded. Hook shaped folds (Type 3) are also seen. The fantastic structures of the region show that there is a shear zone running parallel to the axis of the
synclinoriun. Some workers have suggested that the area is a major transpressional zone with development of a flower structure. The structure of North Delhi Fold belt is well known but relatively lesser data is available from Southern part of Delhi Fold belt. This study has a potential to extract more focused structural information from the SDFB and improve the understanding ofthe Delhi-Aravalli orogeny.

Multiple Paleogene dextral shear zones are identified in the Chugach metamorphic complex (CMC) in southern Alaska providing an unusual down-plunge view of the deformation associated with transpressional strike-slip systems at mid- to lower-crustal levels. Along the northern flank of the CMC, the brittle Stuart Creek fault is structurally continuous with the ductile Harry's Gulch shear zone. Field relationships suggest the brittle fault transfers slip structurally downward into a localized, approximately 2-km-wide shear zone deformed under greenschist-facies conditions. At amphibolite-facies, under mid-crustal conditions, deformation is localized in anastomosing shear zones ranging from 10s of m to 2-3 km in width that are cryptic as they pass downward into lower-crustal migmatitic gneiss. Strike-slip-related deformation in these migmatitic gneisses is more dispersed, suggesting more distributed flow. Absence of a symmetric cleavage fan associated with the steep ductile shear zones and variations in finite strain indicate that an attachment zone model (e.g., Teyssier and Cruz, 2004) is not applicable to the deep crustal structure of the CMC strike-slip system. We discuss two as yet indistinguishable hypotheses to account for the deep crustal structure of the CMC strike-slip system: (1) a narrow detachment zone model where detachment occurs at the metamorphic transition from schist to gneiss, and (2) a differential folding model where crustal-penetrating shear zones are masked by variations in folding mechanisms at different crustal levels.

Multiple Paleogene dextral shear zones are identifi ed in the Chugach metamorphic complex (CMC) in southern Alaska providing an unusual down-plunge view of the deformation associated with transpressional strike-slip systems at mid-to lower-crustal levels. Along the northern fl ank of the CMC, the brittle Stuart Creek fault is structurally continuous with the ductile Harry's Gulch shear zone. Field relationships suggest the brittle fault transfers slip structurally downward into a localized, ~2-km-wide shear zone deformed under greenschistfacies conditions. At amphibolite-facies, under mid-crustal conditions, deformation is localized in anastomosing shear zones ranging from 10's of m to 2-3 km in width that are cryptic as they pass downward into lower-crustal migmatitic gneiss. Strike-slip-related deformation in these migmatitic gneisses is more dispersed, suggesting more distributed fl ow. Absence of a symmetric cleavage fan associated with the steep ductile shear zones and variations in fi nite strain indicate that an attachment zone model (e.g., Teyssier and Cruz, 2004) is not applicable to the deep crustal structure of the CMC strike-slip system. We discuss two as yet indistinguishable hypotheses to account for the deep crustal structure of the CMC strike-slip system: (1) a narrow detachment zone model where detachment occurs at the metamorphic transition from schist to gneiss and (2) a differential folding model where crustal-penetrating shear zones are masked by variations in folding mechanisms at different crustal levels.