Embed Size (px)
Citation preview
Ballarat Geology
https://ballaratgeology.wordpress.com/ballarat-gold-mine/
(and on facebook)
NowDetails at https://ballaratgeology.wordpress.com
Geothermal heat flow and natural electricity flow : slightly wierdogeological datasets that help delineate the regional geological architecture of Victoria.– David Taylor, Senior Geologist
http://earthresources.vic.gov.au/earth-resources/geology-of-victoria/geological-survey-of-victoria
15 Mar, 2018
Nexthttps://ballaratgeology.wordpress.com
?May – OctoberLCT pegmatites, Myanmar turbiditegold, Drones in geology, Gold in Victoria, Lake Boga Granites….
Elsewhere
29 Mar, 6:15. GSA Victoria. Tasmanian conglomerates, Melbourne.21 Mar, 6:30pm GPIC. Granites of central Victoria, and gold -Neil Phillips University13 Apr, 5:30pm. Geopub. Networking, Melbourne.16 Mar, AusIMM, Water – Facts, Perceptions and Conflicts. GD Delprat Distinguished Lecturer Rob Dunn, Bendigo
More details at https://ballaratgeology.wordpress.com
Something to say?
Having interesting and/or relevant talks is important.Do you have something to say or know someone who [email protected]
More details at https://ballaratgeology.wordpress.com
April needs you!!
UNCLASSIFIED
UNCLASSIFIED
Weird geological datasets that help delineate the geology of Victoria:
Geothermal heat flow and natural electricity flow (magneto-tellurics)
David Taylor, Geological Survey of Victoria
UNCLASSIFIED
UNCLASSIFIED
By way of Introduction: Geological Surveys
UNCLASSIFIED
UNCLASSIFIED
Classic geological mapping from 1990’s until mid 2000’s
UNCLASSIFIED
UNCLASSIFIED
• Geothermal heat flow
• Natural Electricity flow (Magneto-Tellurics)
Weird geological datasets that help delineate the geology of Victoria:Geothermal heat flow and natural electricity flow (magneto-tellurics)
UNCLASSIFIED
UNCLASSIFIED
Geothermal is Greek for Hot Earth
The deeper you go, the hotter it gets: 30C/km = 150C @ 5km*
*150C is min commercial temperature and 5 km is max commercial drilling depth
Therefore need better than average for geothermal development
UNCLASSIFIED
UNCLASSIFIED
World Geothermal Electricity output = 10,000 MW
UNCLASSIFIED
UNCLASSIFIED
Exploration so easy a child could do it
UNCLASSIFIED
UNCLASSIFIED
Geothermal Province Map
Victoria not on plate margin but has large intraplate volcanic field
that in places is still young enough to be hot (younger than 40, 000 y)
UNCLASSIFIED
UNCLASSIFIED
Laws of Physics means can use (near) surface heat flow to predict temperature at depth via two stage process (1 then 2)
Heat flow = Conductivity x Temperature Gradient
drilling costs not linear
500 m = $100,000
5000 m = $10,000,000
ie. 10x deeper = 100x $$$
5 km
C x T
C
H?
1
2
T?
UNCLASSIFIED
UNCLASSIFIED
Berrook-1
-350
-300
-250
-200
-150
-100
-50
0
0 25 50 75 100 125 150
Gradient (°C/km)
Depth
(m
)
15 20 25 30 35 40
Temperature (°C)
Gradient
Available Core
Temperature
Collecting heat flow data dots: ∆T x C = H
55 (8%) x 1.30 (7%) = 66 (15%)
30 (4%) x 2.4 (8%) = 72 (12%)
69 (10%)
Warina sand
Olney mud
Olney sand
Olney mud
Duddo limestone59 (4%)
32 (7%)
50 (7%)
UNCLASSIFIED
UNCLASSIFIED
Berrook-1
-350
-300
-250
-200
-150
-100
-50
0
0 25 50 75 100 125 150
Gradient (°C/km)
Depth
(m
)
15 20 25 30 35 40
Temperature (°C)
Gradient
Available Core
Temperature
Collecting heat flow data dots: ∆T x C = H
55 (8%) x 1.30 (7%) = 66 (15%)
30 (4%) x 2.4 (8%) = 72 (12%)
69 (10%)
Warina sand
Olney mud
Olney sand
Olney mud
Duddo limestone59 (4%) x 1.30 (7%) = 77 (11%)
32 (7%) x 2.5 (12%) = 79 (19%)
75 (9%)50 (7%) x 1.4 (10%) = 70 (17%)
UNCLASSIFIED
UNCLASSIFIED
Acquire measurements, join dots and colour in (crustal heat flow typically 50-100 mW/m)
From 7 – (10) historic To 175 – (240) new
77
97
90
52
43
129
52
Traffic lights
Quality estimates:
Green is good
Yellow is acceptable
Red is a worry
UNCLASSIFIED
UNCLASSIFIED
Sm 60
Sa 64
S1 80
Sm 75
S9 47V3 70
V14 77
S11 63
S7 47
Enough dots to make map for first time and see pattern
s
G 97
B 86
Bellarine 1: 90±9
Nepean 38: 83±3
Tynong 1: 85±4
S 95
Green is the typical value for crust
UNCLASSIFIED
UNCLASSIFIED
Sm 60
Sa 64
S1 80
Sm 75
S9 47V3 70
V14 77
S11 63
S7 47
Fundamental crustal blocks are visible
s
F
G 97
B 86
Bellarine 1: 90±9
Nepean 38: 83±3
Tynong 1: 85±4
Delamerian
Fold Belt
Stawell &
Bendigo
Selwyn
Block
UNCLASSIFIED
UNCLASSIFIED
• Geothermal heat flow
• Natural Electricity flow (Magneto-Tellurics)
Weird geological datasets that help delineate the geology of Victoria:Geothermal heat flow and natural electricity flow (magneto-tellurics)
UNCLASSIFIED
UNCLASSIFIED
Fantastic variation in rocks with altered rocks being orders of magnitude different
UNCLASSIFIED
UNCLASSIFIED
Magnetotellurics (MT) is easy to deploy and very low impact because using a natural electrical signal (unlike I.P)
UNCLASSIFIED
UNCLASSIFIED
Electrodes and magnetometers measuring in X-Y-(Z)advances in computing power can now model in 3D
UNCLASSIFIED
UNCLASSIFIED
More time gives more signal-to-noise and therefore better resolution at depth
UNCLASSIFIED
UNCLASSIFIED
‘Mini Grid’ done in western Victoria over the young Volcanics
Are anomalies at base of crust magma activity?
2D fence diagram cross-sections Surface map plot projections
UNCLASSIFIED
UNCLASSIFIED
State Wide grid collected by Federal AusLamp project
anomalies look to be related to Granites rather than Volcanics in full 3D space?
UNCLASSIFIED
UNCLASSIFIED
Fundamental crustal blocks again apparent in this dataset
Delamerian
Fold Belt
Stawell &
Bendigo
Selwyn BlockDelamerian
Fold Belt
Stawell &
Bendigo
Selwyn Block
UNCLASSIFIED
UNCLASSIFIED
Good match of fundamental crust boundaries in both MT and heat flow
Delamerian
Fold Belt
Stawell &
Bendigo
Selwyn BlockDelamerian
Fold Belt
Stawell &
Bendigo
Selwyn Block
UNCLASSIFIED
UNCLASSIFIED
• Recent geothermal work collected enough dedicated
data to make a map for first time
• Same for magnetolluric data
• Both datasets (flow of electricity and flow of heat) are
fundamental physics processes and earth properties so
perhaps no surprise they confirm geology shapes
based on mapping and seismic etc?
IN CONCLUSION
UNCLASSIFIED
UNCLASSIFIED
7=BZ LFB seismic line, 8=Echuca parallel line, 9= DFB seismic,
12= DFB infill (kate), 14= SZ gap infill (michael), 16 south parallel (hugh)
Victorian deep seismic
12
16
14
7
8
9
