Interpretation of an Aneromagnetic Survey Over the Butcher Ridge Igneous Complex, Transantarctic Mountains

对横贯南极山脉屠夫岭火成岩杂岩的风磁测量的解释

• 批准号: 9814036
• 负责人: John Behrendt
• 金额: $ 5万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-08-01 至 2003-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9814036&HistoricalAwards=false
• 关键词: Interpretation; Aneromagnetic; Survey; Over; Butcher

This award, provided by the Antarctic Geology and Geophysics Program of the Office of Polar Programs, supports research to analyze and interpret aeromagnetic data collected over the Butcher Ridge Igneous Complex (BRIC) in the Transantarctic Mountains. These data were collected as a draped aeromagnetic survey in 1997-98 as part of the larger Transantarctic Mountains Aerogeophysical Research Activity (TAMARA) survey. TAMARA was conducted as a cooperative project between US investigators and the German Federal Institute for Geosciences and Natural Resources (BGR).The BRIC, located in the Transantarctic Mountains at about 79 degrees 45 minutes S and 156 degrees E, is exposed in a 10-km-long, 600-m-high scarp, projecting through and bounding the East Antarctic ice sheet. Only part of the BRIC has been mapped geologically because of its inaccessibility. The BRIC appears to be a sill-like hypabyssal intrusion ranging in composition from tholeiitic basalt to rhyolite. A 40Ar/39Ar age of 174 Ma and the chemical character of the basaltic rocks show the BRIC to be part of the widespread Jurassic Ferrar suite of continental tholeiitic rocks. This suite, that extends for over 3000 km across Antarctica, is the result of magmatic activity associated with the Jurassic Transantarctic (failed) rift, and comprises the Ferrar Dolerite sills (the great bulk of the exposures) and dikes, the extrusive Kirkpatrick Basalt flows and the massive gabbroic Dufek intrusion.Significant volumes of crustal-derived rhyolite within the BRIC, requiring a substantial source of advective heat to be formed by melting of crustal rocks, suggested that a major high-level basaltic intrusion might underlie it. In 1990 a single aeromagnetic profile was obtained as part of a BGR-USGS survey over the adjacent Ross Ice Shelf. This profile showed an 8-km-wide positive anomaly with maxima of about 700 and 1000 nT (nano-Tesla), and was interpreted using magnetic models to indicate a gabbroic body beneath the BRIC 2-km thick. This interpretation implied that Ferrar magmatism was accompanied by large, upper crustal magma chambers in which assimilation-fractional crystallization occurred.In 1997-98, a 2.5 by 20-km line spaced, draped aeromagnetic survey was flown by helicopter over the BRIC as part of the TAMARA survey. A preliminary compilation of the aeromagnetic survey over the BRIC shows a 1200-nT amplitude series of anomalies roughly associated with the topography. It is apparent that the high amplitude anomaly pattern, first crossed by the single 1990 profile, is more extensive than the 10-km wide exposed outcrop. The highest amplitude anomalies appear south of the profile acquired in 1990, and extend out of the survey area. The new aeromagnetic data will allow determination of the extent of the thick cumulate body beneath exposures of Beacon sedimentary rock and ice in the survey area as well as beneath the small BRIC exposure. Working in cooperation with the BGR in Germany and the NSF supported PI's of the TAMARA survey, this award supports a detailed analysis and interpretation of the aeromagnetic survey over the area covering Butcher Ridge and the inferred buried extent of the BRIC. Two and three-dimensional models will be calculated, and in cooperation with the USGS, various derivative maps (e.g. pseudogravity gradients and magnetic terraces) will be produced. The models will be interpreted in terms of induced, and if possible, remnant magnetization for the mafic cumulate body inferred to underlie the BRIC and surrounding area.Ultimately, this research will lead to comparisons between the magnetic signature of the BRIC to the patterns of magnetic variation observed over the Ross Sea, the Ross Ice Shelf, and over the ice covered area of the Byrd Subglacial Basin through which the West Antarctic Ice Sheet (WAIS) flows. This comparative work is important to interpretations of possible volcanic features beneath the WAIS that are inferred from magnetic anomaly maps in that region.

该奖项由极地计划办公室的南极地质和地球物理学计划提供，支持研究，以分析和解释跨天然山脉的屠夫岭火成岩复合物（BRIC）收集的航空磁数据。这些数据是在1997 - 98年作为悬垂的航空磁性调查收集的，这是较大的跨北极山航空地球物理研究活动（Tamara）调查的一部分。塔玛拉（Tamara）是在美国调查人员与德国联邦地球科学与自然资源研究所（BGR）之间进行的合作项目。位于跨抗山脉的金砖四国，约79度45分钟S和156摄氏度E，在10千米长的600米高的疤痕中暴露在600米长的疤痕中，并在600米长的疤痕中暴露，并贴在东道和东那天，并限制了Ice Speep。由于其无法获取，因此仅在地质上绘制了一部分。金砖四物似乎是一种凹槽状的hypapyssal侵入，范围从tholeiitic玄武岩到流纹岩的组成。 174 Ma的40AR/39AR年龄和玄武岩岩石的化学特征表明，金砖四国成为大陆Tholeiitic Rocks的广泛侏罗纪Ferrar Suite的一部分。这套套件遍布整个南极的3000公里，是与侏罗纪跨二巨头（失败）裂谷相关的岩浆活动的结果，包括铁岩凹槽（大部分暴露）和dikes和Dikes，dikes and Dikes，繁重的Kirkpatrick Baselt Flow和Massive Gabbbrroics dufek dufekbrroic dufek.在金砖四国内的地壳衍生的流纹岩，需要通过熔化的地壳岩石形成大量的对流来源，这表明主要的高水平玄武岩侵入可能是基础的。在1990年，作为BGR-USGS调查的一部分，在相邻的Ross Ice架上获得了单个航空磁性轮廓。该轮廓显示出8公里宽的正异常，最大值约为700和1000 nt（纳米 - tesla），并使用磁模型来解释，以指示在厚度为2 km的厚度下方的gabbroic体。这种解释暗示，法拉岩浆伴有大型的上层岩浆腔室，在其中发生同化 - 分裂的结晶。在1997 - 98年，在塔玛拉（Tamara）调查的一部分中，由直升机上的直升机在底架上飞行了2.5 x 20公里的间隔，悬垂的航空电磁调查。对金砖四物的航空磁调查的初步汇编表明，与地形大致相关的1200 nt振幅序列序列。显然，首先由单个1990年轮廓交叉的高振幅异常模式比10公里宽的露出露头更广泛。最高的振幅异常出现在1990年获得的轮廓以南，并扩展到调查区域。新的航空磁数据将允许在调查区域的信标沉积岩石和冰的暴露下以及小砖的暴露下确定厚累积物体的范围。该奖项与德国的BGR合作，NSF支持了塔玛拉调查的PI，该奖项支持了涵盖Butcher Ridge的空气磁调查的详细分析和解释，并支持Butcher Ridge和Bric的推断埋藏范围。将计算两个和三维模型，并与USGS合作，将产生各种衍生图（例如，伪层梯度和磁性露台）。这些模型将以诱导的含量累积的体系来解释。流。这种比较工作对于解释从该区域中磁异常图推断出的WAI下的可能的火山特征。