Magnetic anomaly grid of the Lightning Creek Sill Complex, Australia¶

This is a section of an airborne survey acquired in 1990 by the Queensland Government, Australia. The grid has 50 m resolution (UTM coordinates) and is at a uniform orthometric height of 500 m.

Original source: Geophysical Acquisition & Processing Section 2019. MIM Data from Mt Isa Inlier, QLD (P1029), magnetic line data, AWAGS levelled. Geoscience Australia, Canberra

Pre-processing: Source code for preparation of the original dataset for redistribution in Ensaio

import pygmt
import xarray as xr

import ensaio

Download and cache the data and return the path to it on disk

fname = ensaio.fetch_lightning_creek_magnetic(version=1)
print(fname)

Out:

/home/runner/work/_temp/cache/ensaio/v1/lightning-creek-magnetic-grid.nc

Load the netCDF grid with xarray

data = xr.load_dataarray(fname)
data

<xarray.DataArray 'total_field_anomaly' (northing: 370, easting: 346)>
array([[  35.        ,   36.19995   ,   36.69995   , ..., -101.099976  ,
        -100.400024  ,  -99.599976  ],
       [  36.5       ,   37.599976  ,   38.        , ..., -102.20007   ,
        -101.5       , -100.70007   ],
       [  37.099976  ,   38.19995   ,   38.599976  , ..., -103.30005   ,
        -102.599976  , -101.900024  ],
       ...,
       [ 182.79993   ,  172.40002   ,  160.79993   , ...,    0.79992676,
         -24.200073  ,  -41.80005   ],
       [ 182.09998   ,  172.59998   ,  161.40002   , ...,    6.        ,
         -21.5       ,  -41.        ],
       [ 178.79993   ,  170.40002   ,  160.29993   , ...,   11.400024  ,
         -16.        ,  -35.80005   ]], dtype=float32)
Coordinates:
  * easting   (easting) float64 4.655e+05 4.656e+05 ... 4.827e+05 4.828e+05
  * northing  (northing) float64 7.576e+06 7.576e+06 ... 7.595e+06 7.595e+06
    height    (northing, easting) float64 500.0 500.0 500.0 ... 500.0 500.0
Attributes:
    Conventions:   CF-1.8
    title:         Magnetic total-field anomaly of the Lightning Creek sill c...
    crs:           proj=utm zone=54 south datum=WGS84 units=m no_defs ellps=W...
    source:        Interpolated from airborne magnetic line data using gradie...
    license:       Creative Commons Attribution 4.0 International Licence
    references:    Geophysical Acquisition & Processing Section 2019. MIM Dat...
    long_name:     total-field magnetic anomaly
    units:         nT
    actual_range:  [-1785.  3798.]

Make a PyGMT pseudo-color map of the total field magnetic anomaly.

fig = pygmt.Figure()
scale = 2500
pygmt.makecpt(cmap="polar+h", series=[-scale, scale], background=True)
fig.grdimage(
    grid=data,
    cmap=True,
    shading="+a45+nt0.1",
    projection="X15c/17c",
    frame="af",
)
fig.colorbar(
    frame='af+l"total field magnetic anomaly [nT]"',
    position="JBC+h+o0/1c+e",
)
fig.show()

Out:

<IPython.core.display.Image object>

The anomaly at the top right is the Lightning Creek sill complex.

Total running time of the script: ( 0 minutes 5.157 seconds)

Gallery generated by Sphinx-Gallery

Ensaio v0.5.0

Magnetic anomaly grid of the Lightning Creek Sill Complex, Australia

Magnetic anomaly grid of the Lightning Creek Sill Complex, Australia¶