Palaeochannels near West Wyalong, New South Wales: A case study in delineation and modelling using aeromagnetics
Palaeochannels near West Wyalong, New South Wales: A case study in delineation and modelling using aeromagnetics
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新南威尔士州西怀厄朗附近的古河道：利用航磁进行描绘和建模的案例研究
DOI：
10.1071/eg00001
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发表时间：
2000
期刊：
影响因子：
--
通讯作者：
R. Evans
中科院分区：
文献类型：
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作者：
T. Mackey;K. Lawrie;P. Wilkes;T. Munday;N. D. S. Kovacs;R. Chan;D. Gibson;C. Chartres;R. Evans
1998年11月，澳大利亚地质调查局(AGSO)和新南威尔士州矿产资源部在新南威尔士州西怀隆以北相距50米、距地面60米的线上获得了高分辨率的航空磁谱和伽马能谱数据。此外，AGSO还对吉尔莫断裂带南面西怀隆和图尔马之间的一个区域的类似高分辨率的专有数据集进行了后处理。在这些数据集中已经识别出由古河道沉积引起的异常。航空磁性数据的模拟被用来确定古河道沉积的几何形状。这些模型使用钻孔和井下磁化率测量的数据进行了约束。填图古河道沉积对矿产勘查和水土保持研究具有潜在意义。从历史上看，冲积金占澳大利亚黄金产量的很大一部分，通常是古河道赋存的。研究区域是历史悠久的怀龙金矿的一部分，也是布兰德克里克古山谷的一部分。古河道沉积也可能是含盐地下水的储集层，因此在开发旱地盐碱化灾害评估的水文地质模型方面具有重要意义。由于其埋藏深度(通常隐藏在表层沉积物之下，深达150米)，研究区的古河道沉积可以使用航空磁力或电磁数据进行填图，但不能使用伽马能谱进行填图。古河道沉积物中含有集中在砂土和粘土中透镜体中的碎屑状铁质岩浆鱼岩(具有极高的磁化率)。将航磁数据集的分辨率与不同采集参数的调查结果进行了比较。这些测试表明，以小于100米的线距飞行的航空地球物理测量可以揭示有关风化物质的重要信息，包括河道充填沉积，例如在Bland Creek古山谷的沉积充填中。
In November 1998, the Australian Geological Survey Organisation (AGSO) and the New South Wales Department of Mineral Resources acquired high-resolution airborne magnetic and gamma-ray spectrometric data along lines spaced 50 m apart and 60 m above ground level north of West Wyalong, New South Wales. In addition,AGSO post-processed a proprietary dataset of similarly high-resolution from an area immediately to the south, between West Wyalong and Temora, along the Gilmore Fault Zone. Anomalies interpreted to be caused by palaeochannel deposits have been identified in these datasets. Modelling of the airborne magnetic data was used to define the geometry of the palaeochannel deposits. These models were constrained using data from drill holes and downhole magnetic susceptibility measurements. Mapping palaeochannel deposits is of potential significance for mineral exploration and land and water research. Historically, alluvial gold, often palaeochannel-hosted, has accounted for a large proportion of Australia’s gold production. The study area is part of the historic Wyalong Goldfield and is part of the Bland Creek palaeovalley. Palaeochannel deposits may also be reservoirs of saline groundwater, and therefore are important in developing hydrogeological models for dryland salinity hazard assessment. Due to their depth of burial (often concealed beneath surficial sediments, to depths of 150 m), the palaeochannel deposits in the study area are mappable using either airborne magnetic or electromagnetic data, but not using gamma-ray spectrometry. The palaeochannel deposits contain detrital ferruginous maghaemitic pisoliths (which have extremely high magnetic susceptibility) concentrated in lenses in sand and clay. The resolution of the aeromagnetic datasets is compared with results obtained from surveys with different acquisition parameters. These tests suggest that an airborne geophysical survey flown with line spacing of less than 100 m can reveal important information about regolith materials, including channel-fill deposits such as in the sedimentary fill of the Bland Creek palaeovalley.