The plutonic rocks of the Antarctic Peninsula magmatic arc form one of the major batholiths of the circum-Pacific rim. The Antarctic Peninsula batholith is a 1350 km long by < 210 km wide structure which was emplaced over the period ˜240 to 10 Ma, with a Cretaceous peak of activity that started at 142 Ma and waned during the Late Cretaceous. Early Jurassic and Late Jurassic–Early Cretaceous gaps in intrusive activity probably correspond to episodes of arc compression. In a northern zone of the Antarctic Peninsula, the batholith intrudes Palaeozoic–Mesozoic low-grade meta-sedimentary rocks, and in a central zone it intrudes schists and ortho- and paragneisses which have Late Proterozoic Nd model ages and were deformed during Triassic to Early Jurassic compression. In a southern zone the oldest exposed rocks are Permian sedimentary rocks and deformed Jurassic volcanic and sedimentary rocks. All these pre-batholith rocks formed a belt of relatively immature crust along the Gondwana margin. With few exceptions, Jurassic plutons crop out only within the central zone: many are peraluminous, having ‘S-like’ mineralogies and relatively high 87sr/86sri. They are considered to consist largely of partial melts of upper crust schists and gneisses and components of mafic magmas that caused the partial fusion. By contrast, Early Cretaceous plutons crop out along the length of the batholith. Few magma compositions appear to have been affected by upper crust, the bulk being compositionally independent of the type of country rock they intrude. They are dominated by metaluminous, calcic, Si-oversaturated, 1-type granitoid rocks with relatively low 87sr/86sri intermediate-silicic compositions (< 5% MgO). We interpret these to represent partial melts of basic to intermediate, igneous, locally garnet-bearing, lower crust. Contemporaneous mafic magmas (e.g. syn-plutonic dykes) form a more alkaline, Si-saturated series having higher 143Nd/144Nd at the same87sr/86sr than the intermediate-silicic series, to which they are not petrogenetically related. The change from limited partial fusion of upper crust in Jurassic times to widespread partial fusion of lower crust in Early Cretaceous times is considered to be a result of an increasing volume of basaltic intrusion into the crust with time.
January 26, 2018 Governor Wolf to Enlist Non-Partisan Mathematician to Evaluate Fairness of Redistricting Maps SHARE Email Facebook Twitter National Issues, Press Release, Redistricting, Voting & Elections Harrisburg, PA – Governor Wolf today announced he will enlist a non-partisan mathematician, Moon Duchin, Ph.D. an Associate Professor of Mathematics from Tufts University, to provide him guidance on evaluating redistricting maps for fairness. Governor Wolf has made clear since the Supreme Court ruled the map unconstitutional that he saw this as an opportunity to eliminate partisan gerrymandering and deliver the people of Pennsylvania a fair Congressional map.“Moon Duchin has been a leader in applying mathematics, geometry, and analytics to evaluate redistricted maps and work to eliminate extreme partisan gerrymandering,” Governor Wolf said. “The people of Pennsylvania are tired of partisan games and gridlock – made worse by gerrymandering – and it is my mission to reverse the black-eye of having some of the worst gerrymandering in the country. I am open and willing to work with the General Assembly but I will not accept an unfair map and enlisting a non-partisan expert is essential to ensure that is possible.”Biography:Moon Duchin is an Associate Professor of mathematics at Tufts University and serves as director of Tufts’ interdisciplinary Science, Technology, and Society program. Her mathematical research is in geometric group theory, low-dimensional topology, and dynamics. She is also one of the leaders of the Metric Geometry and Gerrymandering Group, a Tisch College-supported project that focuses mathematical attention on issues of electoral redistricting.Duchin’s research looks at the metric geometry of groups and surfaces, often by zooming out to the large scale picture. Lately she has focused on geometric counting problems, in the vein of the classic Gauss circle problem, which asks how many integer points in the plane are contained in a disk of radius r. Her graduate training was in low-dimensional topology and ergodic theory, focusing on an area called Teichmüller theory, where the object of interest is a parameter space for geometric structures on surfaces.Duchin has also worked and lectured on issues in the history, philosophy, and cultural studies of math and science, such as the role of intuition and the nature and impact of ideas about genius. She is involved in a range of educational projects in mathematics: she is a veteran visitor at the Canada/USA Mathcamp for talented high school students, has worked with middle school teachers in Chicago Public Schools, developed inquiry-based coursework for future elementary school teachers at the University of Michigan, and briefly partnered with the Poincaré Institute for Mathematics Education at Tufts.Education:PhD in Mathematics, University of Chicago, 2005MS in Mathematics, University of Chicago, 1999BA in Mathematics and Women’s Studies, Harvard University, 1998Curriculum Vitae: Moon Duchin CV.pdf read more