Petrogenesis of the Masirah ophiolite Me'lange at Ras Madraka, Oman

2020 ◽  
Author(s):  
Sobhi Nasir
Keyword(s):  
Indian Ocean ◽  
Large Scale ◽  
Volcanic Rocks ◽  
Geochemical Data ◽  
Metamorphic Rocks ◽  
Rock Types ◽  
Tectonic Events ◽  
History Of ◽  
The Indian Ocean

<p>The Masirah nappes are represented by allochthonous Late Jurassic to Cretaceous volcanic rocks and ophiolites well as Permian to Maastrichtian marine sediments, obducted onto the Oman continental margin at the cretaceous/Tertiary boundary (Schreurs and Immenhauser, 1999). The Masirah ophiolite forms a straight NNE-SSW trending strip 40 km wide, extending 450 km from Ras Madrakah to the Batain coast. The ophiolite is truncated by the ophiolitic mélange (known as Masirah Mélange) which makes a high angle with the sheeted dike trend and has been interpreted as a transform fault zone (Moseley and Abbotts 1979). The Masirah Mélange shows all the features characteristic of a tectonic mélange, in particular indefinite, non-stratigraphic, contacts and scanty matrix, indicating that it is not a diapiric mélange (Shackletonet and Ries.1990). The blocks within the mélange range in size from several kilometers to a few meters and are composed of blocks of all the rock types of the ophiolite beside metamorphic rocks. Metamorphic rocks from RasMedraka Mélange are mainly composed amphibolite, two mica gneiss, and schist. The amphibolite consists of hornblende, plagioclase, clinopyroxene, sphene, chlorite, epidote, calcite, quartz, biotite, prehnite, magnetite, and ilmenite. Geochemical data shows amphibolites have similar MORBgeochemical characteristics. The Masirah ophiolite and mélange preserve a very long (80 Ma) history of igneous and sedimentary activity prior to emplacement onto the Arabian continental crust. However, dating of the mélange is so far proving difficult. It clearly post-dates the main ophiolite and pre-dates the early Tertiary (Shackletonet al. 1990).</p><p>This study is focused on providing age constraints for the amphibolite and greenschist facies metamorphic rocks of the Masirah Mélange in Ras Madraka by 40Ar ⁄ 39Ar dating. All 40Ar ⁄ 39Ar results were obtained in the ALF Argonlab, Freiberg University, Germany.  Most of the samples show large degrees of Ar-loss or, in some cases, the presence of an excess Ar component, reflected by disturbed age spectra. In general, however, the large number of temperature steps measured in one hornblende sample allows the determination of well-constrained inverse isochron ages that generally provide a more robust error estimate than plateau ages. Laser stepwise heating of these hornblende samples yielded flat age spectra with plateau ages of 83.8+0.96 Ma.</p><p>The Indian Ocean was characterized by stepwise breakup of east and west Gondwana at 157 Ma, breakup of east Gondwana at 130 Ma, Madagascar and India/Seychelles at 95–84 Ma, India and Seychelles at 65 Ma, and, finally at40 Ma, rifting between Africa and Arabia Peters, 2000; Nasir 2016). The range from 160 Ma to 80 Ma suggests that magmatic activity in the Masirah ophiolite was more or less continuous over a period of ~80 Ma, and correlates with large-scale tectonic events recorded in the early Indian Ocean at 80-160 Ma. The 40Ar ⁄ 39Ar ages indicate that hornblende formed before 84 Ma and this age can be interpreted as cooling ages dating approximately the formation of the plastic deformation and abduction. We attribute the Masirah Mélange to the Madagascar and India/Seychelles breaking event at 95–84.</p>

Lamprophyres, lamproites and related rocks as tracers to supercontinent cycles and metallogenesis

2021 ◽  
pp. SP513-2021-159
Author(s):  
Lukáš Krmíček ◽  
N. V. Chalapathi Rao
Keyword(s):  
Large Scale ◽  
Mantle Metasomatism ◽  
Future Research ◽  
Special Publication ◽  
Rock Types ◽  
Tectonic Events ◽  
Geodynamic Processes ◽  
History Of ◽  
Future Research Directions

AbstractProterozoic to Cenozoic lamprophyres, lamproites and related rock types hold a unique potential for the investigation of processes affecting mantle reservoirs. They originated from primary mantle-derived melts that intruded both cratons and off-craton regions, that were parts of former supercontinents - Columbia, Rodinia and Gondwana-Pangea. Well-known for hosting economic minerals and elements such as diamonds, base metals, platinum-group elements and Au, they are also significant for our understanding of deep-mantle processes, such as mantle metasomatism and mantle plume-lithosphere interactions, as well as large-scale geodynamic processes, including subduction-related tectonics, supercontinent amalgamation and break-up, respectively. This Special Publication presents an overview of the state-of-the-art and recent advances as achieved by individual research groups from different parts of the world, and outlines future research directions. Mineralogical, geochemical, geochronological and isotope analyses are used to decipher the complex petrogenetic and metallogenetic evolution of these extraordinary rocks, and unravel a complete history of tectonic events related to individual supercontinent cycles. The Special Publication including this introductory chapter also deals with some issues related to the classification of these rocks.

Editorial Introduction

2020 ◽  
Vol 4 (1) ◽  
pp. 1
Author(s):  
Editors of the JIOWS
Keyword(s):  
Nineteenth Century ◽  
Indian Ocean ◽  
Western Indian Ocean ◽  
Late Nineteenth Century ◽  
Fourth Volume ◽  
History Of ◽  
The Indian Ocean ◽  
Complex Relationships ◽  
Indian Ocean World ◽  
Shed Light

The editors are proud to present the first issue of the fourth volume of the Journal of Indian Ocean World Studies. This issue contains three articles, by James Francis Warren (Murdoch University), Kelsey McFaul (University of California, Santa Cruz), and Marek Pawelczak (University of Warsaw), respectively. Warren’s and McFaul’s articles take different approaches to the growing body of work that discusses pirates in the Indian Ocean World, past and present. Warren’s article is historical, exploring the life and times of Julano Taupan in the nineteenth-century Philippines. He invites us to question the meaning of the word ‘pirate’ and the several ways in which Taupan’s life has been interpreted by different European colonists and by anti-colonial movements from the mid-nineteenth century to the present day. McFaul’s article, meanwhile, takes a literary approach to discuss the much more recent phenomenon of Somali Piracy, which reached its apex in the last decade. Its contribution is to analyse the works of authors based in the region, challenging paradigms that have mostly been developed from analysis of works written in the West. Finally, Pawelczak’s article is a legal history of British jurisdiction in mid-late nineteenth-century Zanzibar. It examines one of the facets that underpinned European influence in the western Indian Ocean World before the establishment of colonial rule. In sum, this issue uses two key threads to shed light on the complex relationships between European and other Western powers and the Indian Ocean World.

Australianama

2019 ◽  
Author(s):  
Samia Khatun
Keyword(s):  
Indian Ocean ◽  
South Asian ◽  
South Asian Diaspora ◽  
Post Cold War ◽  
Asian Diaspora ◽  
Broken Hill ◽  
History Of ◽  
The Indian Ocean ◽  
Anglophone World ◽  
Indian Ocean World

Australian deserts remain dotted with the ruins of old mosques. Beginning with a Bengali poetry collection discovered in a nineteenth-century mosque in the town of Broken Hill, Samia Khatun weaves together the stories of various peoples colonized by the British Empire to chart a history of South Asian diaspora. Australia has long been an outpost of Anglo empires in the Indian Ocean world, today the site of military infrastructure central to the surveillance of 'Muslim-majority' countries across the region. Imperial knowledges from Australian territories contribute significantly to the Islamic-Western binary of the post- Cold War era. In narrating a history of Indian Ocean connections from the perspectives of those colonized by the British, Khatun highlights alternative contexts against which to consider accounts of non-white people. Australianama challenges a central idea that powerfully shapes history books across the Anglophone world: the colonial myth that European knowledge traditions are superior to the epistemologies of the colonized. Arguing that Aboriginal and South Asian language sources are keys to the vast, complex libraries that belie colonized geographies, Khatun shows that stories in colonized tongues can transform the very ground from which we view past, present and future.

The Paving Stone Theory of World Tectonics

2018 ◽  
Author(s):  
Roy Livermore
Keyword(s):  
Indian Ocean ◽  
Plate Tectonics ◽  
Earth Science ◽  
Transform Faults ◽  
Plate Motions ◽  
Euler’S Theorem ◽  
History Of ◽  
New Ideas ◽  
Entire History ◽  
The Indian Ocean

Tuzo Wilson introduces the concept of transform faults, which has the effect of transforming Earth Science forever. Resistance to the new ideas is finally overcome in the late 1960s, as the theory of moving plates is established. Two scientists play a major role in quantifying the embryonic theory that is eventually dubbed ‘plate tectonics’. Dan McKenzie applies Euler’s theorem, used previously by Teddy Bullard to reconstruct the continents around the Atlantic, to the problem of plate rotations on a sphere and uses it to unravel the entire history of the Indian Ocean. Jason Morgan also wraps plate tectonics around a sphere. Tuzo Wilson introduces the idea of a fixed hotspot beneath Hawaii, an idea taken up by Jason Morgan to create an absolute reference frame for plate motions.

scholarly journals Evolution of the Distribution of Upper-Tropospheric Humidity over the Indian Ocean: Connection with Large-Scale Advection and Local Cloudiness

2017 ◽  
Vol 56 (7) ◽  
pp. 2035-2052 ◽  
Author(s):  
Thomas Garot ◽  
Hélène Brogniez ◽  
Renaud Fallourd ◽  
Nicolas Viltard
Keyword(s):  
Indian Ocean ◽  
Large Scale ◽  
Transport Model ◽  
Intraseasonal Variability ◽  
Back Trajectory ◽  
Time Step ◽  
Air Masses ◽  
Upper Troposphere ◽  
Upper Tropospheric Humidity ◽  
The Indian Ocean

AbstractThe spatial and temporal distribution of upper-tropospheric humidity (UTH) observed by the Sounder for Atmospheric Profiling of Humidity in the Intertropics by Radiometry (SAPHIR)/Megha-Tropiques radiometer is analyzed over two subregions of the Indian Ocean during October–December over 2011–14. The properties of the distribution of UTH were studied with regard to the phase of the Madden–Julian oscillation (active or suppressed) and large-scale advection versus local production of moisture. To address these topics, first, a Lagrangian back-trajectory transport model was used to assess the role of the large-scale transport of air masses in the intraseasonal variability of UTH. Second, the temporal evolution of the distribution of UTH is analyzed using the computation of the higher moments of its probability distribution function (PDF) defined for each time step over the domain. The results highlight significant differences in the PDF of UTH depending on the phase of the MJO. The modeled trajectories ending in the considered domain originate from an area that strongly varies depending on the phases of the MJO: during the active phases, the air masses are spatially constrained within the tropical Indian Ocean domain, whereas a distinct upper-tropospheric (200–150 hPa) westerly flow guides the intraseasonal variability of UTH during the suppressed phases. Statistical relationships between the cloud fractions and the UTH PDF moments of are found to be very similar regardless of the convective activity. However, the occurrence of thin cirrus clouds is associated with a drying of the upper troposphere (enhanced during suppressed phases), whereas the occurrence of thick cirrus anvil clouds appears to be significantly related to a moistening of the upper troposphere.

scholarly journals Coffee: An Indian Ocean Perspective

2016 ◽  
Vol 11 (2) ◽  
pp. 61-81
Author(s):  
Shane J. Barter
Keyword(s):  
Indian Ocean ◽  
South Asia ◽  
Latin American ◽  
Eastern Africa ◽  
Coffee Production ◽  
Production And Consumption ◽  
History Of ◽  
Coffee Farmers ◽  
The Indian Ocean ◽  
Indian Ocean World

Abstract Studies of coffee production and consumption are dominated by emphases on Latin American production and American consumption. This paper challenges the Atlantic perspective, demanding an equal emphasis on the Indian Ocean world of Eastern Africa, the Middle East, South Asia, and Southeast Asia. A geographical approach to historical as well as contemporary patterns of coffee production and consumption provides an opportunity to rethink the nature of coffee as a global commodity. The Indian Ocean world has a much deeper history of coffee, and in recent decades, has witnessed a resurgence in production. The nature of this production is distinct, providing an opportunity to rethink dependency theories. Coffee in the Indian Ocean world is more likely to be produced by smallholders, countries are less likely to be economically dependent on coffee, farmers are more likely to harvest polycultures, and countries represent both consumers and producers. A balanced emphasis of Atlantic and Indian Ocean worlds allows us to better understand coffee production and consumption, together telling a more balanced, global story of this important commodity.

Interannual Rainfall Extremes over Southwest Western Australia Linked to Indian Ocean Climate Variability

2006 ◽  
Vol 19 (10) ◽  
pp. 1948-1969 ◽  
Author(s):  
Matthew H. England ◽  
Caroline C. Ummenhofer ◽  
Agus Santoso
Keyword(s):  
Indian Ocean ◽  
Western Australia ◽  
Wind Field ◽  
Large Scale ◽  
Extreme Rainfall ◽  
Ekman Transport ◽  
Eastern Indian Ocean ◽  
Basin Scale ◽  
Rainfall Extremes ◽  
The Indian Ocean

Abstract Interannual rainfall extremes over southwest Western Australia (SWWA) are examined using observations, reanalysis data, and a long-term natural integration of the global coupled climate system. The authors reveal a characteristic dipole pattern of Indian Ocean sea surface temperature (SST) anomalies during extreme rainfall years, remarkably consistent between the reanalysis fields and the coupled climate model but different from most previous definitions of SST dipoles in the region. In particular, the dipole exhibits peak amplitudes in the eastern Indian Ocean adjacent to the west coast of Australia. During dry years, anomalously cool waters appear in the tropical/subtropical eastern Indian Ocean, adjacent to a region of unusually warm water in the subtropics off SWWA. This dipole of anomalous SST seesaws in sign between dry and wet years and appears to occur in phase with a large-scale reorganization of winds over the tropical/subtropical Indian Ocean. The wind field alters SST via anomalous Ekman transport in the tropical Indian Ocean and via anomalous air–sea heat fluxes in the subtropics. The winds also change the large-scale advection of moisture onto the SWWA coast. At the basin scale, the anomalous wind field can be interpreted as an acceleration (deceleration) of the Indian Ocean climatological mean anticyclone during dry (wet) years. In addition, dry (wet) years see a strengthening (weakening) and coinciding southward (northward) shift of the subpolar westerlies, which results in a similar southward (northward) shift of the rain-bearing fronts associated with the subpolar front. A link is also noted between extreme rainfall years and the Indian Ocean Dipole (IOD). Namely, in some years the IOD acts to reinforce the eastern tropical pole of SST described above, and to strengthen wind anomalies along the northern flank of the Indian Ocean anticyclone. In this manner, both tropical and extratropical processes in the Indian Ocean generate SST and wind anomalies off SWWA, which lead to moisture transport and rainfall extremes in the region. An analysis of the seasonal evolution of the climate extremes reveals a progressive amplification of anomalies in SST and atmospheric circulation toward a wintertime maximum, coinciding with the season of highest SWWA rainfall. The anomalies in SST can appear as early as the summertime months, however, which may have important implications for predictability of SWWA rainfall extremes.

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