The southern portion of the Sao Francisco Palaeocontinent in Brazil is denoted by Archean nuclei and Paleoproterozoic magmatic arcs that were amalgamated during Siderian to Orosirian orogenic processes (ca. 2.4–2.1 ​Ga). New isotopic U–Pb in zircon and Sm–Nd whole rock combined with major and trace element composition analyses constrain the crystallization history of the Neoarchean Piedade block (at ca. 2.6 ​Ga) and the Paleoproterozoic Mantiqueira Complex (ca. 2.1–1.9 ​Ga). These therefore display quite different magmatic histories prior to their amalgamation at ca. 2.05 ​Ga. Sm–Nd and Rb–Sr isotopes imply a mixed mantle-crustal origin for the samples in both units. A complete Palaeoproterozoic orogenic cycle, from subduction to collision and collapse, is recorded in the Piedade Block and the Mantiqueira Complex. Rhyacian to Orosirian subduction processes (ca. 2.2–2.1 ​Ga) led to the generation of coeval (ca. 2.16 ​Ga) TTG suites and sanukitoids, followed by late (2.10–2.02 ​Ga) high-K granitoids that mark the collisional stage. The collisional accretion of the Mantiqueira Complex against the Piedade Block at 2.08–2.04 ​Ga is also recorded by granulite facies metamorphism in the latter terrane, along the Ponte Nova suture zone. The collisional stage was closely followed by the emplacement of within-plate tholeiites at ca. 2.04 ​Ga and by alkaline rocks (syenites and enriched basic rocks) at ca. 1.98 ​Ga, marking the transition to an extensional tectonic regime. The discovery of two episodes of TTG and sanukitoid magmatism, one during the Neoarchean in the Piedade Complex and another during the Rhyacian in the Mantiqueira Complex, indicates that the onset of subduction-related melting of metasomatized mantle was not restricted to Neoarchean times, as generally believed, but persisted much later into the Paleoproterozoic.

Neoarchean and Rhyacian TTG-Sanukitoid suites in the southern São Francisco Paleocontinent, Brazil: evidence for diachronous change towards modern tectonics

Evidence for a complex accretionary history preceding the amalgamation of Columbia: The Rhyacian Minas-Bahia Orogen, southern São Francisco Paleocontinent, Brazil

A comprehensive tectonic evolution of Proterozoic to Cambrian rocks that integrate the crystalline basement of Rio de Janeiro State, based on the new geological map, is presented. The map combines detailed geological data integrated to a 1:400.000 scale and new geochemical and geochronology data to characterize the distinct terranes amalgamated during three pulses of the Brasiliano orogeny. The Occidental terrane comprises the Tonian to Late Cryogenean passive margin of the Sao Francisco paleocontinent, including reworked cratonic basement. At the same period, two magmatic arc systems were developed outboard: The Continental Inner arc system represented by the dismembered terranes (Paraiba do Sul, Embu, and Cambuci domain) integrated now in the Central Superterrane: and the Intra-oceanic Outer Arc System, the Oriental Terrane, developed from 860 to 620 Ma. Related active basins were detected in association with the two arc systems that collided at ca. 620 - 595 and 605 - 550 Ma against the Sao Francisco passive margin. A later collision episode at ca. 535 to 510 Ma brought the Cabo Frio Terrane (Angola tip) and closed the Buzios back-arc basin. Finally, the collapse of the orogenic belt, probably related to slab detachment and asthenosphere upwelling marks transition to Gondwana stabilization.

/pdf/proterozoic-to-ordovician-geology-and-tectonic-evolution-of-2yz0nku0gi.pdf

Proterozoic to Ordovician geology and tectonic evolution of Rio de Janeiro State, SE-Brazil: insights on the central Ribeira Orogen from the new 1:400,000 scale geologic map

The core of garnet porphyroblasts in the garnet-sillimanite gneiss from Skallevikshalsen, Lü tzow-Holm Complex, East Antarctica, includes Cl-rich (>0.3wt%Cl) biotite and nanogranite/felsite inclusions (former granitic melt). These are estimated to be stable at >1.2 GPa and 820-850 C. Rare occurrence of matrix biotite suggests almost complete consumption of pre-existed matrix biotite during prograde to peak metamorphism. Brine infiltration during prograde to peak metamorphism is supported by Cl-rich scapolite described in previous studies [e.g., 1]. Brine infiltration and progress of continuous biotite-consuming melting reactions were probably responsible for elevating the Cl content of biotite. In situ electron microprobe U-Th-Pb dating of monazite and the in situ LA-ICPMS U-Pb dating of zircon in the garnet-sillimanite gneiss revealed that both monazite and zircon has the ‘older age population’ with ca. 650-580 Ma and the ‘younger age population’ with ca. 560-500 Ma. The REE and trace element pattern of one of the P-rich patches in the garnet core is different from the P-rich garnet rim. The isotope mapping of the same patch by LA-ICPMS revealed that the patch is also observed as a domain depleted in V, Y, Ho, Er, Tm, Yb, and Lu. Clear difference in V concentration between the patch and the rim of the garnet suggests that this patch is not a continuous part from the garnet rim, but is likely a relic of preexisted garnet. Kyanite included in the patch suggests that mediumto high-pressure type metamorphic rock was the precursor. Presence of the older age population (ca. 650-580 Ma) monazites in Skallevikshalsen and Skallen [2] also suggest that rocks in these areas experienced polymetamorphism, and resetting by the ca. 560-500 Ma metamorphic event was incomplete. Taking into account the presence of Cl-rich biotite inclusions in garnet, infiltration of brine accompanied by partial melting is one probable event that took place at ca. 560-500 Ma in the Skallevikshalsen area, and part of the monazite possibly recrystallized by this brine infiltration. References: [1] Satish-Kumar et al., 2006, JMG. [2] Hokada and Motoyoshi, 2006, Polar Geosci.

Possible polymetamorphism and brine infiltration recorded in the garnet-sillimanite gneiss, Skallevikshalsen, Lützow-Holm Complex, East Antarctica

The Congo Basin: Stratigraphy and subsurface structure defined by regional seismic reflection, refraction and well data

Eoarchean to Neoproterozoic crustal evolution of the Mantiqueira and the Juiz de Fora Complexes, SE Brazil: Petrology, geochemistry, zircon U-Pb geochronology and Lu-Hf isotopes

The Zambezi Belt in southern Africa has been regarded as a part of the 570–530 Ma Kuunga Orogen formed by a series of collision of Archean cratons and Proterozoic orogenic belts. Here, we report new petrological, geochemical, and zircon U-Pb geochronological data of various metamorphic rocks (felsic to mafic orthogneiss, pelitic schist, and felsic paragneiss) from the Zambezi Belt in northeastern Zimbabwe, and evaluate the timing and P-T conditions of the collisional event as well as protolith formation. Geochemical data of felsic orthogneiss indicate within-plate granite signature, whereas those of mafic orthogneiss suggest MORB, ocean-island, or within-plate affinities. Metamorphic P-T estimates for orthogneisses indicate significant P-T variation within the study area (700–780 °C/6.7–7.2 kbar to 800–875 °C/10–11 kbar) suggesting that the Zambezi Belt might correspond to a suture zone with several discrete crustal blocks. Zircon cores from felsic orthogneisses yielded two magmatic ages: 2655 ± 21 Ma and 813 ± 5 Ma, which suggests Neoarchean and Early Neoproterozoic crustal growth related to within-plate magmatism. Detrital zircons from metasediments display various ages from Neoarchean to Neoproterozoic (ca. 2700–750 Ma). The Neoarchean (ca. 2700–2630 Ma) and Paleoproterozoic (ca. 2200–1700 Ma) zircons could have been derived from the adjacent Kalahari Craton and the Magondi Belt in Zimbabwe, respectively. The Choma-Kalomo Block and the Lufilian Belt in Zambia might be proximal sources of the Meso- to Neoproterozoic (ca. 1500–950 Ma) and early Neoproterozoic (ca. 900–750 Ma) detrital zircons, respectively. Such detrital zircons from adjacent terranes possibly deposited during late Neoproterozoic (744–670 Ma), and subsequently underwent high-grade metamorphism at 557–555 Ma possibly related to the collision of the Congo and Kalahari Cratons during the latest Neoproterozoic to Cambrian. In contrast, 670–627 Ma metamorphic ages obtained from metasediments are slightly older than previous reports, but consistent with ∼680–650 Ma metamorphic ages reported from different parts of the Kuunga Orogen, suggesting Cryogenian thermal events before the final collision.

https://tsukuba.repo.nii.ac.jp/record/2001240/files/GF_10-6-2021.pdf

Petrology, geochemistry, and zircon U-Pb geochronology of the Zambezi Belt in Zimbabwe: Implications for terrane assembly in southern Africa

Waveform distortion in lossy transmission lines is getting serious in long traces in PCBs in GHz domain. So far this signal-integrity (SI) degradation problem has been solved with some active devices, such as equalizer, pre-emphasizer or de-emphasizer. These devices however require unnecessary power-consumption, cost, and packaging area. We have proposed a novel PCB trace structure called “Segmental Transmission Line (STL)” already in order to reduce reflection noises in the bus wires. In this paper, we firstly apply the STL to restore the waveforms distorted in the lossy transmission line without the active devices. We design and fabricate an STL prototype, and demonstrate that the eye-diagram distorted in the lossy transmission line is improved dramatically more than twice in its eye-height in the STL.

Signal integrity improvement in lossy transmission line using segmental transmission line

Branched traces are strictly prohibited in the routing of printed circuit boards (PCBs) for high-speed data transfer, because they cause serious degradation of the signal integrity (SI) and excessive electromagnetic interference (EMI). If this strong design constraint can be removed, the number of degrees of freedom increases dramatically, and the operation speed in PCBs is expected to be improved significantly. In an attempt to overcome the SI degradation that occurs due to characteristic impedance mismatching, we previously proposed the bio-inspired segmental transmission line (STL), and we demonstrated its effectiveness. In this paper, we apply the STL to a branched trace for high-speed data transfer, and we use genetic algorithms to try to simultaneously improve its SI and EMI. Some branched STL prototypes are fabricated and evaluated, the results, which include eye diagrams and electromagnetic emission intensities, show a big improvement in SI and EMI in branched traces.

Simultaneous Improvement to Signal Integrity and Electromagnetic Interference in High-Speed Transmission Lines

Reply to 'The complex tale of Mantiqueira and Juiz de Fora: A comment on "Eoarchean to Neoproterozoic crustal evolution of the Mantiqueira and the Juiz de Fora Complexes, SE Brazil: Petrology, geochemistry, zircon U-Pb geochronology and Lu-Hf isotopes"' by K. Cutts and C. Lana

Yusuke Kuribara

Papers

Eoarchean to Neoproterozoic crustal evolution of the Mantiqueira and the Juiz de Fora Complexes, SE Brazil: Petrology, geochemistry, zircon U-Pb geochronology and Lu-Hf isotopes

Petrology, geochemistry, and zircon U-Pb geochronology of the Zambezi Belt in Zimbabwe: Implications for terrane assembly in southern Africa

Signal integrity improvement in lossy transmission line using segmental transmission line

Simultaneous Improvement to Signal Integrity and Electromagnetic Interference in High-Speed Transmission Lines

Reply to 'The complex tale of Mantiqueira and Juiz de Fora: A comment on "Eoarchean to Neoproterozoic crustal evolution of the Mantiqueira and the Juiz de Fora Complexes, SE Brazil: Petrology, geochemistry, zircon U-Pb geochronology and Lu-Hf isotopes"' by K. Cutts and C. Lana