Paper Session II-A - Expanding the Commercial Space Arena: The Western Pacific Rim States as Competitors-Markets

Space commerce over the past decade has become a field in transition as comsat markets exponentially expand with prospect for further growth in other areas also very positive. As part of this change process, new competitors are stepping forward. The Russian Federation successor state to the former Soviet Union’s space program represents one facet of that new challenge. Its competitiveness grows directly from its historic status as one of the two first space powers. A more intriguing situation is developing in the Western Pacific Rim states, there space-related activities span the spectrum from fairly comprehensive space programs to states just emerging into the space applications arena. This paper explores these changes and discusses their implications for the United States commercial space effort

Transition of magnetic fabric types in fine-grained sedimentary rocks

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The magnetic anisotropy of chloritoid single crystals

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Modalities of anisotropy of magnetic susceptibility in fine-grained sedimentary rocks deformed in a contraction-dominated setting - A case study of the Central Armorican Domain, Brittany, France

An integrated rock-magnetic and mineralogical approach is performed for a case study of low-grade metasedimentary rocks from the Central Armorican Domain (CAD). The objective is twofold. Firstly, gaining a better understanding of the relation between the mineral sources of magnetic susceptibility and the anisotropy of magnetic susceptibility (AMS). Secondly, verifying whether the magnetic fabrics have a potential as a regional strain marker. For this goal, a lithostratigraphical reference unit, which consists of homogeneous siltstone beds (HSB), is sampled in four distinct research areas, i.e. the Crozon south (CS) and Crozon north (CN) research area on the Crozon peninsula and the Monts d Arrée slate belt (MASB) and Montagnes Noires slate belt (MNSB)research area in the inland CAD.It was found that the magnetic fabrics of the HSB samples from the four research areas dominantly reflect two different magnetic fabric types. On the one hand, a type III intermediate magnetic fabric, which is composed of bedding-parallel and a cleavage-parallel component fabric, and on the other hand, a type IV tectonic magnetic, which reflects a single cleavage-parallel fabric. Hence, the magnetic fabrics seems to show ageneral, progressive evolution that is typical for rocks that have been affected by a coaxial, contraction-dominated deformation. There is, however, no systematic regional pattern in the occurrence of these different magnetic fabric types. Both types occur in all four research areas, whereas the four research areas each have their own typical deformation characteristics.Remanence experiments, low temperature and high-field AMS experiments demonstrate that the magnetic signal of the HSB samples is strongly dominated by their paramagnetic phases. A mineralogical analysis revealed that there is a difference in the paramagnetic mineralogy of the HSBs from the Crozon peninsula, i.e. an anchizonal metamorphic mineral assemblage with white mica and chlorite, and the HSBs from the inland slate belts, i.e. an epizonal metamorphic mineral assemblage with white mica and chloritoid. Because of its strong magnetic susceptibility (high FeO content), chlorite is the dominant mineral in the former mineral assemblage. For the same reason, chloritoid is the dominant magnetic mineral in the epizonal mineral assemblage. As we found that the intrinsic magnetic anisotropy of chloritoid is much stronger than that of chlorite, the magnetic anisotropy from the Crozon peninsula and those from the inland slate belts cannot be compared directly and should be treated separately.An independent texture analysis for a single, chloritoid-bearing specimen of the MASB shows that the orientation of the muscovite, chloritoid and chlorite fabric matches the orientation of the magnetic fabric. However, a calculation of the AMS tensor of a 3-phase model from the obtained mineral fabrics and the intrinsic magnetic anisotropy of these three phases, shows that weighted average of the magnetocrystalline anisotropy of the different phases seems not sufficient to explain the measured magnetic anisotropy. The reason for this discrepancy remains unclear to date. Until this issue is solved, we have to conclude that the anisotropy of the magnetic and mineral fabric do not match and hence, the magnetic fabric cannot be used as a reliable proxy for the mineral fabrics.Despite this shortcoming, there are still a number of conclusion that can be drawn from the regional magnetic fabric datasets. Firstly, besides the influence of the metamorphic mineral assemblage, we found that there are two other boundary conditions that are not stable for the entire dataset and hence, that appear to affect the magnetic fabric development. These are (1) composite magnetic fabric variations due to an influence from the angle between the bedding-parallel and the cleavage-parallel component fabric and (2) compositional variations due to an influence from the quartz to total clay ratio. Therefore, the magnetic anisotropy of the HSBs cannot be uniquely related to the tectonic strain in the CAD, even when the issue of the quantitative relationship between the magnetic and mineral fabric can be clarified. Secondly, by comparing the magnetic fabric development for specimens with similar boundary conditions, we can conclude that for the Crozon peninsula there is generally a higher amount of strain for the CN research area than for the CS research area and for the inland slate belts, there is generally a higher strain for the MASB research than for the MNSB research area.<w:latentstyles deflockedstate="false" defunhidewhenused="true" defsemihidden="true" defqformat="false" defpriority="99"  status: publishe

Regional magnetic fabric study of the homogeneous siltstone beds of the Plougastel Formation in the western Central Armorican Terrane

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AMS analysis of the Crozon fold-and-thrust belt of Central Armorica (Brittany, France)

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Magnetic anisotropy of chloritoid and its significance in magnetic fabric studies of low-grade metamorphic rocks

The magnetocrystalline anisotropy of monoclinic chloritoid, a relatively common mineral in aluminium-rich, metapelitic rocks, has been determined for the first time by measuring the anisotropy of magnetic susceptibility (AMS), using two independent high-field approaches, i.e. (a) directional magnetic hysteresis measurements and (b) torque magnetometry, on a collection of single crystals collected from different tectonometamorphic settings worldwide [Haerinck et al., 2013a]. Magnetic remanence experiments show that all specimens contain ferromagnetic (s.l.) impurities, being mainly magnetite. The determined (paramagnetic) high-field-AMS (HF-AMS) ellipsoids have a highly oblate shape with the minimum susceptibility direction subparallel to the crystallographic c-axis of chloritoid. In the basal plane of chloritoid, though, the HF-AMS can be considered isotropic. The corrected degree of anisotropy (PJHF) is found to be 1.47, which is significantly higher than the anisotropy of most paramagnetic silicates and even well above the frequently used upper limit (i.e. 1.35) for the paramagnetic contribution to AMS of siliciclastic rocks. As there is no apparent relationship between PJHF and the high-field bulk susceptibility, it seems that the remarkably high magnetic anisotropy of chloritoid is not simply the result of more Fe (& Mn) cations and hence, a stronger ferrimagnetic interaction within the basal plane of the chloritoid lattice. Instead, an analysis of the paramagnetic Curie temperature, parallel (θpar.) and perpendicular (θperp.) to the basal plane of the chloritoid crystals, indicates that this pronounced magnetocrystalline anisotropy is related to strong antiferromagnetic exchange interactions in the direction of the crystallographic c-axis (θperp. 0). As a consequence, chloritoid-bearing metapelites with a pronounced mineral alignment can have a high degree of AMS without the need of invoking a significant contribution of strongly anisotropic, ferromagnetic (s.l.) minerals. This is tested by a magnetic fabric study of a particular stratigraphic horizon of Armorican metasiltstones, that covers both an area with chloritoid and white mica-bearing metasiltstones, associated with an epizonal metamorphic grade, and an area with chlorite and white mica-bearing metasiltstones, associated with an anchizonal metamorphic grade [Haerinck et al., 2013b]. It was found that the epizonal chloritoid-bearing metasiltstones show (dominantly paramagnetic) PJ values up to 1.45, whereas the anchizonal, chlorite and white mica-bearing metasiltstones show PJ values only up to 1.27. These observations clearly show that the presence of chloritoid in low-grade metamorphic rocks has a profound impact on the rock’s magnetic fabric (AMS) which can be attributed to the very high intrinsic magnetic anisotropy of chloritoid. Therefore, our work calls for a revised approach of magnetic fabric interpretations in chloritoid-bearing rocks. Haerinck et al. 2013a, JGR-B, 118, 13-13, doi: 10.1002/jgrb.50276. Haerinck et al. 2013b, JGS of London, 170 (2), 263-280, doi: 10.1144/jgs2012-062.status: publishe

Regional Magnetic Fabric Study of the Plougastel Formation in the Western Central Armorican Terrane (Brittany, France)

The western part of the Central Armorican Terrane (WCAT), a low-grade middle- to upper-crustal domain exposed in the Armorican Massif (Brittany, France), is affected by an early Variscan contraction-dominated deformation event. Our work consists of a regional magnetic fabric analysis of homogeneous siltstone beds (HSB) in the Plougastel Formation (Pridolian to Lochkovian) that are exposed in different structural settings and levels of the WCAT. Macroscopically, the HSB’s show no internal bedding fabric. However, the anisotropy of magnetic susceptibility (AMS) systematically reveals a composite magnetic fabric, composed of both a bedding-parallel and a cleavage-parallel magnetic-carrier population. Based on petrography, demagnetization experiments and XRD analyses, we show that the bedding-parallel magnetic signal arises from a subtle rock fabric composed of ferromagnetic minerals with a strong internal anisotropy or Fe-rich phyllosilicates. The cleavage-parallel magnetic-carrier population is composed of micas. Despite a positive correlation between the degree of anisotropy (PJ) and the intensity of the mica XRD peak, the AMS signal arises from a complex interaction between both carrier populations. Thus, low-field AMS of a composite magnetic fabric cannot be used as a strain marker, without a more integrated approach (e.g. anisotropy of anhysteretic remanence magnetization (AARM) and low-temperature AMS).status: publishe

The magnetocrystalline anisotropy of chloritoid single crystals investigated by directional magnetic hysteresis measurements and torque magnetometry

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