Theoretical Spectra of Terrestrial Exoplanet Surfaces

We investigate spectra of airless rocky exoplanets with a theoretical framework that self-consistently treats reflection and thermal emission. We find that a silicate surface on an exoplanet is spectroscopically detectable via prominent Si-O features in the thermal emission bands of 7 - 13 \mu m and 15 - 25 \mu m. The variation of brightness temperature due to the silicate features can be up to 20 K for an airless Earth analog, and the silicate features are wide enough to be distinguished from atmospheric features with relatively high-resolution spectra. The surface characterization thus provides a method to unambiguously identify a rocky exoplanet. Furthermore, identification of specific rocky surface types is possible with the planet's reflectance spectrum in near-infrared broad bands. A key parameter to observe is the difference between K band and J band geometric albedos (A_g (K)-A_g (J)): A_g (K)-A_g (J) > 0.2 indicates that more than half of the planet's surface has abundant mafic minerals, such as olivine and pyroxene, in other words primary crust from a magma ocean or high-temperature lavas; A_g (K)-A_g (J) < -0.09 indicates that more than half of the planet's surface is covered or partially covered by water ice or hydrated silicates, implying extant or past water on its surface. Also, surface water ice can be specifically distinguished by an H-band geometric albedo lower than the J-band geometric albedo. The surface features can be distinguished from possible atmospheric features with molecule identification of atmospheric species by transmission spectroscopy. We therefore propose that mid-infrared spectroscopy of exoplanets may detect rocky surfaces, and near-infrared spectrophotometry may identify ultramafic surfaces, hydrated surfaces and water ice.Comment: Accepted for publication on the Ap

The tectonic evolution of central and Northern Madagascar and its place in the final assembly of Gondwana

Copyright © 2002 by The University of Chicago. All rights reserved.Recent work in central and northern Madagascar has identified five tectonic units of the East African Orogen (EAO), a large collisional zone fundamental to the amalgamation of Gondwana. These five units are the Antongil block, the Antananarivo block, the Tsaratanana sheet, the Itremo sheet, and the Bemarivo belt. Geochronological, lithological, metamorphic, and geochemical characteristics of these units and their relationships to each other are used as a type area to compare and contrast with surrounding regions of Gondwana. The Antananarivo block of central Madagascar, part of a broad band of pre-1000-Ma continental crust that stretches from Yemen through Somalia and eastern Ethiopia into Madagascar, is sandwiched between two suture zones we interpret as marking strands of the Neoproterozoic Mozambique Ocean. The eastern suture connects the Al-Mukalla terrane (Yemen), the Maydh greenstone belt (northern Somalia), the Betsimisaraka suture (east Madagascar), and the Palghat-Cauvery shear zone system (south India). The western suture projects the Al-Bayda terrane (Yemen) through a change in crustal age in Ethiopia to the region west of Madagascar. Our new framework for the central EAO links the Mozambique belt with the Arabian/Nubian Shield and highlights the power of tectonic analysis in unraveling the complex tectonic collage of the EAO.Alan S. Collins and Brian F. Windle

Complex examination of the Upper Paleozoic siliciclastic rocks from southern Transdanubia, SW Hungary—Mineralogical, petrographic, and geochemical study

A vertical section of Upper Paleozoic sandstones from southern Transdanubia (Mecsek-Villány area, Tisza mega-unit, Hungary) has been analyzed for major and trace elements, including rare earth elements (REEs). In addition, the clay mineralogy of the sandstone samples and the petrography and geochemistry of gneiss and granitoid clasts extracted from the associated conglomerates have been determined. Geochemistry of the sandstone samples analyzed in this study shows that these rocks were predominantly derived from a felsic continental source; nevertheless, compositions vary systematically up-section. The Pennsylvanian (Upper Carboniferous) Téseny Formation has higher SiO(2) and lower Na(2)O, CaO, Sr, high field strength element (HFSE), and ΣREE contents relative to the Permian strata. Its high K(2)O and Rb contents together with the presence of abundant illite-sericite suggest a potassium metasomatism in this formation. Clay mineralogy and large ion lithophile element (LILE) contents of the Lower Permian Korpád Formation vary spatially and are interpreted as local variations in composition of the source region and postdepositional conditions. Zr and Hf abundances and REE patterns, however, show that this formation was derived from mature upper continental crust. The Upper Permian Cserdi Formation has higher TiO(2), Th, U, Y, Cr, and heavy (H) REE contents, and higher Cr/Th and Cr/Zr ratios relative to the underlying formations. These trends can be explained by a sedimentary system dominated by highly weathered detritus derived from combined recycled-orogen, basement-uplift, and volcanic-arc provenance in the Téseny Formation, with an increased proportion of less weathered detritus derived from combined volcanic and basement-uplift provenances in the Permian formations. Characteristics of the Cserdi unit may reflect relatively proximal derivation from a felsic volcanic source

Tectonic history of the South Tannuol Fault Zone (Tuva region of the northern Central Asian Orogenic Belt, Russia) : constraints from multi-method geochronology

In this study, we present zircon U/Pb, plagioclase and K-feldspar Ar-40/Ar-39 and apatite fission track (AFT) data along the South Tannuol Fault Zone (STFZ). Integrating geochronology and multi-method thermochronology places constraints on the formation and subsequent reactivation of the STFZ. Cambrian (similar to 510 Ma) zircon U/Pb ages obtained for felsic volcanic rocks date the final stage of STFZ basement formation. Ordovician (similar to 460-450 Ma) zircon U/Pb ages were obtained for felsic rocks along the structure, dating their emplacement and marking post-formational local magmatic activity along the STFZ. Ar-40/Ar-39 stepwise heating plateau-ages (similar to 410-400 Ma, similar to 365 and similar to 340 Ma) reveal Early Devonian and Late Devonian-Mississippian intrusion and/or post-magmatic cooling episodes of mafic rocks in the basement. Permian (similar to 290 Ma) zircon U/Pb age of mafic rocks documents for the first time Permian magmatism in the study area creating prerequisites for revising the spread of Permian large igneous provinces of Central Asia. The AFT dating and Thermal history modeling based on the AFT data reveals two intracontinental tectonic reactivation episodes of the STFZ: (1) a period of Cretaceous-Eocene (similar to 100-40 Ma) reactivation and (2) the late Neogene (from similar to 10 Ma onwards) impulse after a period of tectonic stability during the Eocene-Miocene (similar to 40-10 Ma)

Karakteristik Unsur Jejak Dalam Diskriminasi Magmatisme Granitoid Pulau Bangka

Geologi Pulau Bangka disusun oleh variasi granit sebagai Granitoid Klabat yang tersebar di berbagai lokasi. Unsur jejak dapat diaplikasikan dalam diskriminasi magmatisme dalam pembentukan granitoid tersebut. Tujuan penelitian ini adalah mengetahui karakteristik granitoid yang tersebar di Pulau Bangka berdasarkan geokimia unsur jejak untuk diaplikasikan dalam mempelajari magmatisme, sumber dan situasi tektoniknya.Metode analisis geokimia yang diaplikasikan dengan menggunakan Analisis Aktivasi Neutron (AAN) dan portableX-Ray Fluorescence (pXRF) untuk analisis kualitatif dan kuantitatif pada 27 sampel dari Granitoid Klabat di Pulau Bangka.Hasil penelitian ini menyimpulkan Granitoid Bangka Utara (Belinyu) dan Bangka Tengah sebagai percampuran kerak-mantel dengan afinitas Calc-Alkaline, karakteristik Tipe I sedangkan Granitoid Bangka Selatan dan Barat asal kerak dengan afinitas High-KCalc-Alkaline sebagai Tipe S. Diharapkan diskrimasi magmatisme granitoid bermanfaat dalam memberikan panduan eksplorasi bahan galian nuklir di Pulau Bangka. Geology of Bangka Island consists by variation of granite as Klabat Granitoid scattered in various locations. Trace elements can be applied in magmatism discrimination of granitoid.The purpose of this study was to determine the characteristics Bangka Island granitoid based on trace element geochemistry to be applied in the study of magmatism, source and tectonic situation. Geochemical analyses method used are the Neutron Activation Analysis (NAA) and portableX-Ray Fluorescence (pXRF) for qualitative and quantitative analyses on 27 samples of Klabat granitoid on Bangka Island. This study concluded granitoid East Bangka (Belinyu) and Central Bangka as crust-mantle mixing with affinityCalc-Alkaline, characteristic of I Type while South and West Bangka granitoid crust origin with affinity high K Calc-Alkaline as S Type. Expectedmagmatismdiscrimination ofgranitoidhelpfulin providingradioactive mineral explorationguidein BangkaIsland

Comment on “Bilaterian Burrows and Grazing Behavior at >585 Million Years Ago”

Pecoits et al. (Reports, 29 June 2012, p. 1693) describe bilaterian trace fossils and assign them an Ediacaran age based on the age of a granite interpreted as intrusive. We argue that the granite is not intrusive but in fact represents the basement of the sedimentary succession. Moreover, we show that identical trace fossils occur in nearby Carboniferous-Permian glacigenic rocks.Fil: Gaucher, Claudio. Universidad de la República; UruguayFil: Poire, Daniel Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; ArgentinaFil: Bossi, Jorge. Universidad de la República; UruguayFil: Bettucci Sanchez, Leda. Universidad de la República; UruguayFil: Beri, Angeles. Universidad de la República; Urugua

Rochechouart 2017-Drilling Campaign: First Results

No abstract available

Petrogenesis Batuan Granitoid di Desa Ketro, Kecamatan Tulakan, Kabupaten Pacitan, Provinsi Jawa Timur Berdasarkan Petrografi dan Geokimia

Singkapan granitoid di Desa Ketro, Kecamatan Tulakan, Kabupaten Pacitan, Jawa Timur merupakan salah satu bukti keberadaan batuan plutonik asam di Pulau Jawa. Sejauh ini, keberadaan batuan asam di Pulau Jawa sangat terbatas. Singkapan lainnya dilaporkan terdapat di Meru Betiri, Banyuwangi. Keberadaan granitoid Tulakan ditandai dengan adanya lepasan material kuarsa berukuran kerikil. Secara umum kondisi singkapan granitoid Tulakan sudah dalam kondisi lapuk karena banyaknya vegetasi. Batuan granitoid segar dapat dijumpai pada tebing dan sungai. Penelitian ini bertujuan untuk mengetahui variasi litologi, proses diferensiasi, afinitas magma, tipe granitoid, dan lingkungan tektonik granitoid Tulakan. Metode penelitian yang digunakan adalah observasi lapangan berupa pendeskripsian kondisi singkapan dan pengambilan sampel batuan granitoid. Metode kualitatif meliputi pendeskripsian sayatan tipis batuan granitoid. Metode kuantitatif meliputi analisis geokimia menggunakan X-ray Fluoresence (XRF) dengan hasil berupa konsentrasi oksida utama. Hasil penelitian menunjukkan terdapat tiga jenis litologi di lokasi penelitian, yakni granit, granodiorit, dan andesit. Litologi tersebut didominasi oleh mineral kuarsa, K-feldspar, dan plagioklas. Mineral biotit, piroksen, dan zirkon hadir dalam jumlah yg kecil. Mineral sekunder berupa klorit dan serisit hadir menggantikan mineral mafik dan feldspar. Hasil geokimia menunjukkan proses diferensiasi berjalan normal berupa fraksinasi kristal. Terdapat satu sampel yang terjadi anomali pada K2O. Tingkat afinitas magma berada pada Tholeiitic series hingga Calc-Alkaline series. Nilai A/CNK yang lebih besar dari 1,1 menunjukkan batuan granitoid Tulakan termasuk peraluminous dan tergolong granitoid tipe S yang terbentuk pada daerah Continental Colission Granited melalui proses anateksis yang dibuktikan dengan ketidakhadiran mineral hornblende. Kata kunci: Pacitan, Batuan Asam, Granitoid, Petrogenesi

Geo-structural map of the Laguna Blanca basin (Southern Central Andes, Catamarca, Argentina)

The Laguna Blanca basin is a rhomb-shaped basin located at the SE margin of the Puna plateau in the southern Central Andes (Catamarca, Argentina). An interactive analysis using remote sensing and field mapping enabled us to produce a geo-structural map at a 1:350,000 scale. Satellite images from multispectral sensors (ASTER and Landsat 7 ETM+) and medium resolution Digital Elevation Models (SRTM and ASTER GDEM) were used in order to recognize the structures and main lithologies, which were validated in the field and through laboratory tests (e.g. spectral analysis). The final result is a geo-structural map of the Laguna Blanca basin with a new geological unit subdivision, highlighting its tectonic origin, which appears to be related to a releasing stepover along N-S sinistral strike-slip master faults