2. Desktop Study
This research was conducted using the framework of the PHE concept as the scientific foundation, governing the selection of data sources as well as its synthesis, analysis, and interpretation. Consequently, this data analysis was performed in conjunction with the hydrogen’s known elementary physical and chemical properties.
2.1. Palaeotectonical, Geodynamical and Structural Setting
Deep-reaching structural features such as normal faults, strike-slips and thrust faults, are suggested as probable natural hydrogen degassing conduits
[59] | Vidavskiy, V., & Rezaee, R. (2022). Natural Deep-Seated Hydrogen Resources Exploration and Development: Structural Features, Governing Factors, and Controls. Journal of Energy and Natural Resources, 11(3), 60–81. https://doi.org/10.11648/j.jenr.20221103.11 |
[59]
. In this regard, the area of interest was studied through the prism of the modern tectonic activity involving the major structural elements. Several areas corresponding to the potential structures a.k.a. “chimneys” conveying hydrogen to the surface, were preliminarily identified as prospective for natural hydrogen.
Figure 2. The area of research (yellow polygons), interpreted bedrock geology, and main structural features. The AOI is indicated in red rectangle. From GeoVIEW.WA, 2023 https://geoview.dmp.wa.gov.au/. The legend is available from the source.
The primary AOI is located in Western Australia, along the Darling Fault N-NE Perth, covering the eastern flank of the Northern Perth Basin and the western margin of the Yilgarn Craton (
Figure 2).
The local geology appears to have been studied in much detail by several generations of researchers. From the petrology and lithology viewpoints, formations to the east of the Darling Fault are represented by a series of granitoids and greenstone belts of the Yilgarn Craton (
Figure 3), while the western flank is formed by the sedimentary sequences of the Perth Basin, aged Permian through Cretaceous.
In terms of its tectonic setting, this area is represented by a typical cratonic margin environment, transiting to a sedimentary basin through a series of asymmetric NW-SE striking normal faults, with quite steep dips and deep throws (
Figure 4), indicating that the major faults forming the structural network may detach at greater depths within the basement
. In the area of this research, these faults dip in the W – NW – SW direction.
The Darling Fault is the dominating structural element, extending in the general N-S direction for over 1,100 km and separating the Yilgarn Craton to its east from the Perth Basin to its west. Darling Fault is traced to the deep layers of the crust, possibly extending through the Moho into the top lithospheric mantle, approximately at depths about 38-40 km within the area of research. At a depth of about 6km to 7km below the surface, the Proto-Darling Fault structure was identified, being characterized by a zone of poor to no seismic reflection
[36] | Middleton, M., Wilde, S., Evans, B., Long, A., & Dentith, M. (1993). A Preliminary Interpretation of Deep Seismic Reflection and other Geophysical Data from the Darling Fault Zone, Western Australia. Exploration Geophysics - EXPLOR GEOPHYS, 24. https://doi.org/10.1071/EG993711 |
[36]
.
On the Perth Basin flank to the west of the Darling fault, the Urella (N Moora) and the Muchea (S Moora) oblique faults (effectively half-grabens) form the Irwin and the Barberton terraces, correspondingly. The Dandaragan Trough is located to the west of Moora, contacting with the Moora Group to the east, on the Eastern (craton) flank of the Darling fault, with the latter forming a volcanic–clastic-carbonate shelf-platform sequence
[64] | Wilde, S. A., Nelson, D. R., Australia, G. S. of W., & Resources, W. A. D. of M. and P. (2001). Geology of the Western Yilgarn Craton and Leeuwin Complex, Western Australia: A Field Guide. Geological Survey of Western Australia. https://geodocsget.dmirs.wa.gov.au/ |
[64]
.
The development history of the Perth Basin comprises at least three extension events, followed by the post-rifting sedimentation cycles
. The earliest rifting event took place in the Early Permian (ca. 290Ma) and finally resulted in the early Cretaceous (132-140Ma) Gondwana breakup
[40] | Mory, Arthur, Haig, D., Mcloughlin, S., & Hocking, R. (2005). Geology of the northern Perth Basin, Western Australia. A field guide. Geological Survey of Western Australia Record (Vol. 2005/9). ISBN 1 74168 011 5 |
[40]
followed by the Greater India sub-continent departure from the Western Australian Craton (WAC) agglomerate.
A comprehensive Perth Basin tectonic structures development synthesis was presented by Harris
. According to this research, the system experienced a series of extensional and compressional cycles, alternated by both dextral and sinistral transpressional and transtensional events of a complex geometry.
Some researchers
believe that the rifting processes are still ongoing in the area
[5] | Dentith, M. C., Bruner, I., Long, A., Middleton, M. F., & Scott, J. (1993). Structure of the Eastern Margin of the Perth Basin, Western Australia. Exploration Geophysics, 24(3–4), 455–461. https://doi.org/10.1071/EG993455 |
[5]
, while others directly compare the Darling Fault – Perth Basin structure with the San Andreas fault in California, the USA
[6] | Dentith, M, Long, A., Scott, J., & Bruner, I. (1994). The geometry and phanerozoic history of the Darling Fault and associated structures in the Perth Basin. Perth, WA. Retrieved from https://nla.gov.au/nla.obj-641142486/view |
[20] | Hoskin, T., Regenauer-Lieb, K., & Jones, A. (2015). Deep conductivity anomaly of the Darling Fault Zone - implications for fluid transport in the Perth Basin. ASEG Extended Abstracts, 2015. https://doi.org/10.1071/ASEG2015ab047 |
[47] | Rezaee, R. (2021). Assessment of natural hydrogen systems in Western Australia. International Journal of Hydrogen Energy, 46(66), 33068-33077. https://doi.org/10.1016/j.ijhydene.2021.07.149 |
[48] | Rezaee, R. (2020). Natural Hydrogen System in Western Australia? https://doi.org/10.20944/preprints202010.0589.v1 |
[6, 20, 47, 48]
.
Summarizing, the Darling Fault’s (palaeo)tectonic situation and structural setup allow making several assumptions:
1. The Darling Fault runs very deep into the lower crust and is likely to communicate directly with the top of the lithospheric mantle;
2. The Darling Fault's rifting history accounts for several re-activation cycles, one of those eventually resulted in the Greater India breakup and departure;
3. There might be evidence that nowadays, the Darling Fault is not entirely quiescent, experiencing certain structural activity of the dextral strike-slip nature along its extent.
In regards to the driving forces behind this tectonic activity, there are a number of opinions among the research groups. We tend to support the views expressed by Hoskin et al.
[19] | Hoskin, T., Regenauer-lieb, K., & Jones, A. (2015). A Magnetotelluric survey of the North Perth Basin: A technical case study. ASEG Extended Abstracts, 2015(1), 1–4. https://doi.org/10.1071/ASEG2015ab211 |
[19]
(
Figure 5 and
Figure 7) stipulating that the development model for the Darling Fault zone (DFZ), is best explained by the asymmetric graben structure, a.k.a. the “
core complex” (
Figure 6) according to Buck
[1] | Buck, W. R. (1991). Modes of continental lithospheric extension. Journal of Geophysical Research: Solid Earth, 96(B12), 20161–20178. https://doi.org/10.1029/91JB01485 |
[1]
. Interestingly, the latter researcher described the conditions necessary for such structure development as resulting “from extension at high strain state over a narrow [<100km wide] region”.
This crustal structure development mode also corresponds to the “passive” rifting classification (
Figure 8) by Merle
, who attributed the lithospheric structures’ extension processes to the regional stresses located within the lithosphere, i.e., not involving any mantle “plume” upwelling – as opposed to the “active” rifting requiring such deep activity. Such a “passive” rifting process was dubbed as “lithosphere-activated” by Condie
[2] | Condie, K. C. (1982). Plate tectonics and continental drifts. Pergamon Press, Oxford. |
[2]
.
However, neither of the paper authors cited above have come up with an explanation of a mechanism that could possibly drive such powerful pulling forces enabling the lithosphere extension. In our opinion, this phenomenon could be rationally described by the planet Earth expansion model, according to V. Larin
.
One of the potentially productive structures herein labeled as AOI is located within the northern section of the study area, forming the landscape around the Pinjarrega Lake (
Figure 9). Two major faults, Darling to the east and Urella to the west, are intersecting in – or, more accurately, beneath - the Pinjarrega Lake area, forming a unique cluster of tectonic structural elements, which relationship is depicted in
Figure 4, section F
. The Urella Fault splay sprouting to the east-south-east runs parallel to the Abrolhos Transfer Zone (ATZ) located 3km to 4km to the south. On the eastern flank of the Darling Fault, on the Yilgarn Craton, the NW-SE Yandanooka – Cape Riche Lineament marking the 20-40 mGal step change in gravity roughly aligns with the ATZ on the Perth Basin flank to the east (
Figure 9).
Figure 9. The AOI, Pinjarrega lake, WA interpreted bedrock geology, stratigraphy and structural; tectonic features. Extrapolated fault extensions shown in cherry dotted lines. Modified from GeoVIEW, 2023 https://geoview.dmp.wa.gov.au/. The legend is available from the source.
The Urella fault throw is described as being maximal in the area between 29°40' and 30°05’S latitude
. According to Hoskin
[18] | Hoskin, T. (2017). Assessment of the North Perth Basin for geothermal resources using an integrated geophysical approach. PhD Thesis, the University of Western Australia. https://doi.org/10.26182/5b6105aae9b4d |
[18]
, the basin subsidence in the Northern part of the Perth Basin was predominantly controlled by the Urella Fault, allowing to suggest the latter’s primary role in tectonic processes, as opposed to the Darling Fault. Both the Darling and the Urella faults are believed to be quiescent since the Early Cretaceous; however, their nowadays re-activation is quite possible, resulting in promotion of natural hydrogen degassing activity along the mantle-reaching conduits associated with them.
2.2. Datasets Used
It is very important to properly select the appropriate datasets for the desktop analysis to be performed for an AOI in order to suggest its natural hydrogen potential and, in the best case, to preliminarily identify potential targets for further research, represented by structures conducting natural hydrogen to the surface.
In the course of this research, the comprehensive study of borehole data available for the territory of the state of WA from the open sources was performed with the purpose of obtaining in-depth lithological, petrological and geochemical data. Several interesting observations were made, although some of these were related to the areas outside the AOI boundaries. This dataset provided extremely valuable information on the local structural relationships and contact depths, mineralogy alteration systems location/depth and degree, as well as exact fault positions and directions. These datasets analysis contributed to the preliminarily identification and prioritization of potentially hydrogen-productive subsurface structures.
2.2.1. Deep Seismic, ANT, MOHO Depth
MOHO depth research data may provide valuable information about the mantle proximity to the surface, since the depth of the
Mohorovičić boundary, often referred to as MOHO
, may well become one of the parameters potentially indicative of the natural hydrogen degassing activity.
The first extensive deep seismic study across the Darling Fault took place in 1992, the very comprehensive interpretation of which was performed by Middleton
[36] | Middleton, M., Wilde, S., Evans, B., Long, A., & Dentith, M. (1993). A Preliminary Interpretation of Deep Seismic Reflection and other Geophysical Data from the Darling Fault Zone, Western Australia. Exploration Geophysics - EXPLOR GEOPHYS, 24. https://doi.org/10.1071/EG993711 |
[36]
. One of the most interesting observations was made in relation to the deeper structural extension of the Darling Fault named the Proto-Darling Fault, which was interpreted as a zone lacking any seismic response. The reasoning for the Proto-Darling Fault’s lack of seismic response was offered based on the current geophysical science views, suggesting either a high degree of structural deformation or the “fault shadow” effect (
Figure 10). The extension depth of this structure could not be determined, which allows us to assume that its roots expand deep into the lower crust and/or into the top lithospheric mantle.
Another set of data applicable and quite useful for the natural hydrogen early exploration is provided by the Commonwealth Scientific and Industrial Research Organisation (CSIRO)
in their research of the Earth crust by means of the Ambient Noise Tomography (ANT), involving passive seismic imaging. However, it is crucial to point out that this geophysical method shall be utilized very consciously, by a provider possessing substantial experience with natural hydrogen degassing systems, and with a number of factors taken into account, since the interpretation results greatly depend on a specific tectonic and lithology/petrology context, petrophysical anisotropy, fluidal phases’ contrast, etc.
The analogies from other regions, such as wells Mt Kitty-1, Dukas-1 and especially Magee-1 wells in the Amadeus Basin, the Northern Territory (NT), allow to suggest that along with the Moho proximity depths, the “gradient” of the Moho “hill slope” is quite important, too, see
Figure 11.
In this regard, it seemed worthwhile to include the Moho structure data into account while studying natural hydrogen potential within the AOI, at least at the general consideration level. However, the accuracy of the current Moho mapping provided by the GeoVIEW program does not allow turning this parameter into a significant contributor to the decision-making process.
2.2.2. Remote Sensing - Satellite Imagery, ASTER
These datasets improve the identification of potential “hotspots” at the early stages of exploration.
Hydrogen has a strong emission line at 6563 Å which is imaged by the VNIR and SWIR cameras of remote sensing satellites such as Aster, Landsat and Sentinel-2. The Sentinel-2 camera is a pushbroom sensor. The field of view is 10,980 columns which are collected by arrays of sensors finely calibrated for the gas signature to be the same across the image. H
2 layers provided by Manatee Ltd. are produced by three complementary algorithms: spectral modelling, spectral un-mixing, and spatial modelling, the latter assuming escaping H
2 induces optical turbulence in a scene. The results of these algorithms used for interpretation of Sentinel-2 VNIR and SWIR band imagery are demonstrated in
Figure 12a, b, c, d.
Gases’ emanation activity and concentration are estimated using a spatial and two spectral approaches:
Figure 12. The AOI, Pinjarrega Lake, WA. Satellite imagery: (a) H2 Spectral un-mixing; (b) H2 Synthetic emission spectra; (c) H2 Optical turbulence; (d) “Purified” H2 Optical turbulence; (e) methane CH4; (f) ethane C2H6. H2 readings marked in ppm shown in yellow pins, and Darling Fault shown in a solid pink line. Modified from Google Earth and Manatee Ltd., 2022. Courtesy of Macallum New Energy Ltd.
1. Synthetic emission spectra may be resampled to satellite bandpasses;
2. Optical turbulence: Escaping H2 will cause optical turbulence which may be quantified in an image, and so H2 estimates may be inferred from optical turbulence (OT) rather than direct detection of gas;
3. Spectral un-mixing: Un-mixing into spectral endmembers may be achieved with likely gas spectra identified by their spectra and abundance distribution.
Along with hydrogen projections, other associate gases’ emanation maps appear to be extremely helpful in assessing their degassing activity and the “first choice” areas for initial (preferred) approaching the potentially promising locations:
1. Helium He: this gas very frequently accompanies hydrogen in its surface manifestations, also sharing their de-gassing paths on the way through the top silicate crust to the surface;
2. Ozone O
3 Deficiency: According to the researchers
, hydrogen turns ozone O
3 molecules into oxygen O
2 by reacting with a single oxygen atom having a relatively loose bind with the main O
2 pair of atoms, with water produced as a by-product. However, the emission line for ozone has a peak absorption at a wavelength of 254 nm, which is located in the ultraviolet (UV) light region of the electromagnetic spectrum and too short for Sentinel-2 sensing;
3. Methane CH
4 (
Figure 12e): A recent paper available on the Sentinel Copernicus website
[58] | Varon, D. J., Jervis, D., McKeever, J., Spence, I., Gains, D., and Jacob, D. J.: High-frequency monitoring of anomalous methane point sources with multispectral Sentinel-2 satellite observations, Atmos. Meas. Tech., 14, 2771–2785, https://doi.org/10.5194/amt-14-2771-2021, 2021 |
[58]
develops a simple band ratio algorithm to estimate the CH
4 gas endmember. From the product supplier statistics, methane manifestations statistically coincide with hydrogen degassing signs in ~83% of cases.
Advanced Spaceborne Thermal Emission and Reflection ASTER dataset assists with the identification of mineral associations (
Figure 13) as well as reduction / oxidation (redox) balances. It is supported by a number of platforms. In WA, it is included in the GeoVIEW geoscience platform. ASTER layers offer several types of geochemical and mineralogical data on the Project Area, examples below
:
1. Ferrous Iron Index reflects the Fe2+ relative abundancy, which under certain conditions may indicate the degree of chemical reduction possibly due to hydrogen presence, demonstrating the redox balance shift;
2. Opaque Index, which is a combination of the following: (1) magnetite-bearing rocks (e.g., Banded Iron Formations [BIF]); (2) maghemite gravels; (3) manganese oxides; (4) graphitic shales. (1) and (4) above can be evidence for “reduced” rocks when interpreting redox gradients;
3. Ferric Oxide Content: (1) Mapping transported materials (including palaeochannels) characterised by hematite (relative to goethite); and (2) hematite-rich areas in “drier” conditions (e.g., above the water table) whereas goethite-rich in “wetter” conditions (e.g., at/below the water or areas recently exposed);
4. Quartz Index: Use in combination with the Silica index to more accurately map, for example, quartz rather than poorly ordered silica like opal or other silicates like feldspars and (compacted) clays;
5. Silica Index: Broadly equates to the silica SiO2 content though the intensity (depth) of this feature is also affected by particle size <250 microns.
Figure 13. The AOI, Pinjarrega Lake, WA. ASTER imagery layers: (a) Ferrous Iron Index; (b) Ferric Oxide Content; (c) Gypsum Index; (d) Opaque Index; (e) Quartz Index; (f) Silica Index. Darling Fault zone shown in solid black lines. GeoVIEW.WA https://geoview.dmp.wa.gov.au/. The legend is available from the source.
2.2.3. Geomorphology
This dataset is aimed to identify certain terrain features revealing potential hydrogen manifestations and its activity impressions in landscapes: circular depressions, (palaeo)drainage patterns, sand blows/boils a.k.a. injectites
, etc.
Geomorphology features are very important for natural hydrogen degassing structures research and exploration. However, this criterion has to be analyzed involving a number of factors, such as:
1. Soil substrate: redox (pH) balances, regolith thickness and, in some cases, agricultural activity level;
2. Surface and bedrock geology context, e.g., cratons vs. basins, as well as sedimentary cover thickness;
3. Tectonic developmental history;
4. Structural features and their relationships;
5. Geochemical parameters;
6. Petrology (both concordant and discordant intrusions), petrochemistry (alterations and their sequences) and mineralogy (typical associations) aspects.
Sometimes, the certain geomorphology features such as circular depressions first noted by V. Larin
, sometimes referred to as “
fairy circles” by some researchers, may provide the leads to potentially active hydrogen conducting structures. (The “
fairy circle” term was originally introduced for the certain flora phenomena described in botanic disciplines. We consider the use of this term to describe natural hydrogen geomorphological manifestations on terrain surfaces as scientifically inappropriate.) However, we would like to warn the researchers from relying too much on this feature alone, because of two reasons:
a) Natural hydrogen is quite often detected at the locations having no circular depressions nearby
[59] | Vidavskiy, V., & Rezaee, R. (2022). Natural Deep-Seated Hydrogen Resources Exploration and Development: Structural Features, Governing Factors, and Controls. Journal of Energy and Natural Resources, 11(3), 60–81. https://doi.org/10.11648/j.jenr.20221103.11 |
[59]
, and
b) Our field soil gas detection results confirmed that several very distinctive circular depressions earlier described by the other scholars
[9] | Frery, E., Langhi, L., Mainson, M., & Moretti, I. (2021). Natural hydrogen seeps identified in the North Perth Basin, Western Australia. International Journal of Hydrogen Energy, 46(61), 31158–31173. https://doi.org/10.1016/j.ijhydene.2021.07.023 |
[9]
do not yield any significant levels of hydrogen concentrations (
Figure 14b), possibly due to the migration of the hydrogen conveying “chimney” away from its previous position as a result of complex geodynamical and tectonic factors.
Within the area of this research, there are several clusters of circular depressions studied in the process, with the following H
2 concentrations in the top soil layer (<1m) – see
Figure 14:
1. Pinjarrega Lake (
Figure 14a)
2. Lake Dalaroo (
Figure 14b)
3. Lake Eganu (
Figure 14c)
4. Namban lake system
5. Coonderoo lake
6. Nameless circular structures across the research acreage
Figure 14. Circular depressions studied in AOI: a. Pinjarrega Lake, b. Lake Dalaroo, c. Lake Eganu. H2 readings marked in ppm shown in yellow pins, Darling Fault shown in solid pink line. Modified from Google Earth, 2023.
Interestingly, several of the local land users note that in some cases, circular depression emergence process dynamics could be watched “in real time”, when the subject land plot is owned by the same land user for long enough. The process is described in the following way:
1. First, the gentle hill appears;
2. Then, the top of the hill develops the “sand blow”, with inevitable soil fertility loss and its consequent erosion;
3. Later, the top of the hill starts caving in, forming the “crater”, with its further subsidence;
4. Finally, this “crater” gets filled with fresh water coming up from the deep;
5. Initially, the water is fresh, with the stock readily drinking from it. Later, within several years to decades, water salinity increases to the undrinkable levels.
This process is described pretty much the same way along the entire strike of the northern part of the Darling Fault within the area of research, allowing to suggest the modern geomorphologic activity, apparently being related to the natural hydrogen degassing processes along this regional tectonic structure.
All the examples above demonstrated significant concentrations of hydrogen in soil gas readings, from several hundred ppm to the excess of 2,000ppm (the MX6 unit detection range limit for H
2). The Dalaroo Lake located 2.5km W of the town of Moora makes a significant exception in this regard, with H
2 concentrations not exceeding 38ppm, being of the same order of magnitude with the results achieved by Frery
[9] | Frery, E., Langhi, L., Mainson, M., & Moretti, I. (2021). Natural hydrogen seeps identified in the North Perth Basin, Western Australia. International Journal of Hydrogen Energy, 46(61), 31158–31173. https://doi.org/10.1016/j.ijhydene.2021.07.023 |
[9]
.
Other geomorphology features bearing significant meaning in the process of the early exploration for natural hydrogen are represented by gentle hills with sand “blow-outs” and other expressions of collapse on their summits or very close to them. These structures are associated with hydrogen degassing processes causing water interaction with swelling clay beds immediately close to the surface. Some researchers
explain the presence of the latter by low temperature metasomatic leaching, dubbing this process as hydrothermal argillization.
Circular sand dunes named “sand boils” in Arkansas, USA (
Figure 15), are closely related to seismicity causing liquefaction processes. In the scientific literature, these specific near-surface micro-tectonic and geomorphological features are dubbed as “
injectites”
, a.k.a. “sand dikes”. These structures were studied in the process of conducting this research as well, yielding somewhat significant H
2 readings from several dozen ppm up to 1,000ppm from the shallow (<1m deep) holes. However, due to the extremely high mobility of H
2, it would be unrealistic to expect high readings through the unconsolidated soils e.g., loose dry sands and loams.
The list of geomorphology structures studied within this research and mentioned above is not exhaustive; however, the scope of this paper does not allow expanding further on this subject.
2.2.4. SEEBASE
The importance of this source of geological and geophysical data provided by Geognostics (https://www.geognostics.com/) offering a wealth of information about deep layers and structures cannot be overestimated. In 2022, Geognostics issued a new, updated and more detailed report
[11] | Geognostics Australia Pty Ltd. (2022). Perth Basin SEEBASE structural study and GIS. |
[11]
on the Perth Basin structural geology, as well as on its development history. Interestingly, the latter mostly comprises the extensional events, supporting the vision of the Perth Basin posing as a major rifting structure.
The meticulously detailed 3D image of the Perth Basin is shown in
Figure 16, allowing to see the relationships between the major tectonic units.
Figure 16. Oblique 3D view of the Perth Basin, (a) North to South; (b) South to North. From Geognostics Australia Pty Ltd. 2022 https://nla.gov.au/nla.obj-3135827579/view.
2.2.5. Conductivity Data
This dataset provides knowledge
[19] | Hoskin, T., Regenauer-lieb, K., & Jones, A. (2015). A Magnetotelluric survey of the North Perth Basin: A technical case study. ASEG Extended Abstracts, 2015(1), 1–4. https://doi.org/10.1071/ASEG2015ab211 |
[20] | Hoskin, T., Regenauer-Lieb, K., & Jones, A. (2015). Deep conductivity anomaly of the Darling Fault Zone - implications for fluid transport in the Perth Basin. ASEG Extended Abstracts, 2015. https://doi.org/10.1071/ASEG2015ab047 |
[19, 20]
about the deep structures potentially associated with hydrogen activity.
Electric resistivity/conductivity data plays an important role in natural hydrogen studies
. Structurally speaking, conductive protrusions identified by magnetotellurics (MT) electrical resistivity data acquisition may be interpreted as pre-cursors for the early reconnaissance of the natural hydrogen potential. Therefore, positive conductivity anomalies could possibly become the indicators of hydrogen degassing activity nearby and/or of its reactive products’ presence in the system.
In the specialized literature, there is no shortage of attempts to explain the prominence and the existence of highly conductive structures discovered in impressive quantities around the world, with early systematic attempts dating back to early 1990s
[24] | Jones, A. G. (1992). Electrical conductivity of the continental lower crust. Continental Lower Crust, 81–143. |
[24]
. Several mechanisms are proposed to explain this phenomenon, every each of them being scrutinized and eventually rejected, for the following reasons:
1.
Graphite films binding rock grains: large grain size in the lower crust supporting resistivity
[24] | Jones, A. G. (1992). Electrical conductivity of the continental lower crust. Continental Lower Crust, 81–143. |
[24]
; low mobility of carbon
[24] | Jones, A. G. (1992). Electrical conductivity of the continental lower crust. Continental Lower Crust, 81–143. |
[24]
; lack of possibility to stay interconnected for hundreds of km due to the limited stability of grain-boundary films
[24] | Jones, A. G. (1992). Electrical conductivity of the continental lower crust. Continental Lower Crust, 81–143. |
[51] | Selway, K. (2014). On the Causes of Electrical Conductivity Anomalies in Tectonically Stable Lithosphere. Surveys in Geophysics, 35(1), 219–257. https://doi.org/10.1007/s10712-013-9235-1 |
[24, 51]
; thermal stability of graphite, especially in regards to its irreversible dehydration processes
; tectonic stresses permanently breaking the graphite connection pathways
; higher interfacial energy and larger dihedral angle between graphite and olivine
[68] | Zhang, B., & Yoshino, T. (2017). Effect of graphite on the electrical conductivity of the lithospheric mantle. Geochemistry, Geophysics, Geosystems, 18(1), 23–40. https://doi.org/10.1002/2016GC006530 |
[68]
.
2.
Mylonite petrology: low frequency of occurrence within the Darling Fault region
[20] | Hoskin, T., Regenauer-Lieb, K., & Jones, A. (2015). Deep conductivity anomaly of the Darling Fault Zone - implications for fluid transport in the Perth Basin. ASEG Extended Abstracts, 2015. https://doi.org/10.1071/ASEG2015ab047 |
[20]
.
3.
Fluids in porous zones: this model requires an unrealistically high percentage of pores, over 10%
[24] | Jones, A. G. (1992). Electrical conductivity of the continental lower crust. Continental Lower Crust, 81–143. |
[24]
or even between 10% and 30%, based on the gravity model estimates
[20] | Hoskin, T., Regenauer-Lieb, K., & Jones, A. (2015). Deep conductivity anomaly of the Darling Fault Zone - implications for fluid transport in the Perth Basin. ASEG Extended Abstracts, 2015. https://doi.org/10.1071/ASEG2015ab047 |
[20]
; depth constraints posed by the requirement to have permeability pathways, which contradicts the seismic quiescence of the Darling fault estimates
[20] | Hoskin, T., Regenauer-Lieb, K., & Jones, A. (2015). Deep conductivity anomaly of the Darling Fault Zone - implications for fluid transport in the Perth Basin. ASEG Extended Abstracts, 2015. https://doi.org/10.1071/ASEG2015ab047 |
[20]
.
4.
Partial melt: temperature, [shallow] depth and mineralogy constraints
[24] | Jones, A. G. (1992). Electrical conductivity of the continental lower crust. Continental Lower Crust, 81–143. |
[51] | Selway, K. (2014). On the Causes of Electrical Conductivity Anomalies in Tectonically Stable Lithosphere. Surveys in Geophysics, 35(1), 219–257. https://doi.org/10.1007/s10712-013-9235-1 |
[24, 51].
According to the PHE concept, the mantle is composed of inter-metallic substance
[30] | Larin, V. N. (1993). Hydridic Earth: The New Geology of Our Primordially Hydrogen-Rich Planet. (W. Hunt, Ed.). Calgary: Polar Publishing. ark:/13960/t1ng6db6d ISBN-10: 0969450621, ISBN-13:978-0969450627 |
[30]
. In the certain tectono-structural environments, this substance may protrude closer to the surface, resulting in a number of geophysical, geochemical and geomorphological consequences
.
These wedge-looking structures formed by intermetallic silicides (
Figure 17) shall come up as extremely strong conductors on the resistivity cross-sections. During the past couple of decades, with the massive arrival of fundamental research data, this model of the planet structure and composition was confirmed by a number of independent researchers. In particular, Rohrbach
[49] | Rohrbach, A., Ballhaus, C., Ulmer, P., Golla-Schindler, U., & Schoenbohm, D. (2011). Experimental Evidence for a Reduced Metal-saturated Upper Mantle. J. Petrol., 52, 717–731. https://doi.org/10.1093/petrology/egq101 |
[49]
stated that “More than 75 vol.% of the Earth’s present-day mantle is likely to be saturated with metallic iron.”
Figure 17. A diapir of the “abnormal mantle” (intermetallic silicides), in the zone of a modern continental rifting. Modified from V. Larin, 2005 (rus). Translation 2020 – unpublished.
Other researchers
[7] | Dentith, Mike, Evans, S., Thiel, S., Gallardo, L., Joly, A., & Romano, S. S. (2013). A magnetotelluric traverse across the southern Yilgarn Craton. Geological Survey of Western Australia. |
[51] | Selway, K. (2014). On the Causes of Electrical Conductivity Anomalies in Tectonically Stable Lithosphere. Surveys in Geophysics, 35(1), 219–257. https://doi.org/10.1007/s10712-013-9235-1 |
[7, 51]
admit that the presence of hydrogen is likely to increase formations’ conductivity, e.g., through the ionic to proton diffusion transit mechanism in Fe, Mg silicates with depth
. The latter perfectly correlates with the PHE concept conclusions in regard to the transit of covalent and ionic bonds between hydrogen and various metals under pressure
.
There are two known deep MT transects available for the areas adjacent to the research area:
C.II.6.i. New Norcia (NN) MT Transect
[19] | Hoskin, T., Regenauer-lieb, K., & Jones, A. (2015). A Magnetotelluric survey of the North Perth Basin: A technical case study. ASEG Extended Abstracts, 2015(1), 1–4. https://doi.org/10.1071/ASEG2015ab211 |
[20] | Hoskin, T., Regenauer-Lieb, K., & Jones, A. (2015). Deep conductivity anomaly of the Darling Fault Zone - implications for fluid transport in the Perth Basin. ASEG Extended Abstracts, 2015. https://doi.org/10.1071/ASEG2015ab047 |
[19, 20]
, which was run along the earlier deep seismic transect. It was acquired in 2011, running W - E crossing the Darling Fault south of New Norcia. This transect offers a very comprehensive set of data regarding regional structural lineaments, some of them extending into the research area.
Later, this transect was re-interpreted by T. Hoskin for his PhD Thesis
[18] | Hoskin, T. (2017). Assessment of the North Perth Basin for geothermal resources using an integrated geophysical approach. PhD Thesis, the University of Western Australia. https://doi.org/10.26182/5b6105aae9b4d |
[18]
. Remarkably, the conductive bodies associated with the main tectonic structural features are still very much recognizable in this latest interpretation.
The conductive zones in the western section of the transect were interpreted to be closely related to the Muchea (UF) and the Darling (DFZ) Faults (stations NN05 and NN06, correspondingly), apparently running upwards towards the surface from the deeper geospheres, while the latter possibly communicate with the mantle beneath the Moho. This explains the role of the Darling Fault serving as a conduit for deep-seated hydrogen, conveying it to the surface.
C.II.6.ii. Coorow – Green Head (CGH) MT Transect, which was shot between 2011 and 2014. Data interpretation was performed immediately upon this project's completion and revealed several conductive structures associated with the deep faults crossed by this transect. Same as for the NN MT transect in C.II.6.i above, the CGH transect originally interpreted in 2015 was also re-interpreted by T. Hoskin in 2017 for his PhD Thesis
[18] | Hoskin, T. (2017). Assessment of the North Perth Basin for geothermal resources using an integrated geophysical approach. PhD Thesis, the University of Western Australia. https://doi.org/10.26182/5b6105aae9b4d |
[18]
.
It is well seen that on the craton flank of the Darling Fault (central to eastern part of the transect), deep faults apparently communicating with the lower crust and, most likely, with the upper mantle, quite often demonstrate their affinity with the conductive structures extending to great depths, possibly beyond the Moho. Quite contrary, the very pronounced conductivity anomalies in the Perth Basin (central to western part of the transect) seem to be relatively shallow, not expanding too deep.
2.2.6. Tectonic Stresses, Seismicity; Tectonics, Geodynamics, Petrology
In-situ tectonic stress analysis is essential for understanding the current extension/compression regime/s
[46] | Reynolds, S., Coblentz, D., & Hillis, R. (2002). Tectonic forces controlling the regional intraplate stress field in continental Australia: Results from new finite element modeling. J. Geophys. Res., 8150. https://doi.org/10.1029/2001JB000408 |
[46]
. It may assist with the task of assessing both regional and local forces acting in the crust, potentially either promoting or inhibiting natural hydrogen and other gases’ migration processes.
For certain reasons, in-situ tectonic stresses in general
are mostly studied for the purpose of assessing regional seismicity risks and predicting earthquakes
. Therefore, such research is concentrated on the orientation (azimuth) vector as well as on its absolute force and/or its magnitude - but not on the compression/tension regimes, which is quite understandable, with consideration of the main purpose of such studies.
The majority (53%) of reliable data for in-situ tectonic stresses is provided by means of analyzing physical defects occurring in the process of well drilling: break-outs (43%), DITF - drilling-induced tensile fractures (8%), and over-coring processes (2%)
. However, it is important to bear in mind that these analyses start bearing sensible meaning below the certain depths – for the wells where such measurements are taken, not being the case for the majority of shallow mining and geotechnical operations. For this reason, the number of analyzed boreholes is limited to deeper (petroleum) wells.
At any rate, the study we conduct on tectonic stresses potentially affecting hydrogen degassing paths through deeper geospheres requires data from much greater depths, currently inaccessible by means of conventional drilling.
The commonly accepted viewpoint
[25] | Kennett, B. L. N., Chopping, R., & Blewett, R. (2018). The Australian Continent: A Geophysical Synthesis. ANU Press and Geoscience Australia, Canberra. https://press-files.anu.edu.au/downloads/press/n4442/pdf/book.pdf |
[44] | Rajabi, M., Tingay, M., Heidbach, O., Hillis, R., & Reynolds, S. (2017). The present-day stress field of Australia. Earth-Science Reviews, 168, 165–189. https://doi.org/10.1016/j.earscirev.2017.04.003 |
[25, 44]
suggests mostly compressional stresses for the SW of the Australian continent.
Other researchers
[32] | Lee, M., Mikula, P., Mollison, L., & Litterbach, J. (2008). Stresses in the Australian continental tectonic plate-variability and likely controls. In Presentation to the Australian Earthquake Engineering Society Annual Meeting, Ballarat, VIC. https://aees.org.au/wp-content/uploads/2013/11/32-Lee.pdf |
[32]
who base their conclusions on the practical work results, however, disagree with this mainstream viewpoint, proposing mostly extensional mode for the majority of Australian megastructures. Noticeably, the stipulated stress magnitudes suggest the maximal value of 90 MPa for the Yilgarn Craton, as well as the complete lack of (significant) compression zones for the entire continent.
This latter view agrees with the PHE concept, according to which the majority of global tectonic structures are subjected to the stress modes represented by extension not compression, primarily due to the acknowledgement of the expanding planet model
.
The vision of extension tectonic stresses prevailing in the research area is supported by the earlier researchers
, at least in its western part – see the Perth Basin (western) flank in
Figure 18.
Studying earthquakes epi- and hypocenters allows to assess their relationship with structural features
and, potentially, with deep hydrogen-conveying magmatic bodies. For the AOI, the majority of the known earthquakes are concentrated to the east across the Darling Fault (Calingiri, Cardoix) -SE (Meckering), within the Yilgarn Craton terranes. Within the Perth Basin, the seismicity is insignificant, which may be attributed to the crystalline basement rock thicknesses of up to 14,000m; sedimentary basin formations do not transfer the shocks that easily, effectively muffling them to hardly noticeable magnitudes.
This dataset assists with identification of potential hydrogen migration pathways from deeper geospheres towards the surface along the petrophysically weakened irregularities and anisotropy vectors – See Palaeotectonical, Geodynamical and Structural Setting above.
Same as above, intrusive bodies’ contact zones represented by altered mineralogy associations offer a great opportunity for forming natural hydrogen conduits.
2.2.7. Radiometry
The results of the recent work done by a group of European researchers
[43] | Prinzhofer, A., Rigolett, C., Berthelot, J., & Francolin, J. (2022). Gamma spectrometry as the best proxy for hydrogen exudations. In 1st Natural Hydrogen Worldwide Summit. |
[43]
, who noticed a correlation between the natural hydrogen degassing manifestations on the surface and Th and U concentrations in the top soil layers. According to this research, high concentrations of Th and low U/Th ratios correlate with high H
2 concentration anomalies.
Figure 19. The AOI, Pingarrega Lake: (a) Thorium Th concentrations in ppm; (b) U/Th ratio. Warmer colors represent higher values. H2 reading in ppm. Modified from GA https://portal.ga.gov.au/. The legend is available from the source.
The GA website (https://portal.ga.gov.au/) offers the maps of Th concentrations and U/Th ratio (
Figure 19a and
Figure 19b, correspondingly). For some locations where H
2 presence was detected, these maps demonstrate significant levels of radiometry data correlation with soil gas measurements for the bulk of the structure, whilst there is little or no correlation, at all for others.
Overall, in our opinion, this technique may benefit from conducting further practical research performed in-situ, with comparisons to be made between the desktop studies and the results of the soil gas detection in the field.
2.2.8. Soils
This parameter may be used for determining redox balances and forecasting the field conditions while planning soil gas sampling campaigns.
For Western Australia, we were unable to find this data layer readily available in GeoVIEW or any other system supported by the state, compared to how it is quite comprehensively done in South Australia, being offered through the South Australian Resource Information Gateway (SARIG) platform (https://map.sarig.sa.gov.au/).
Based on data available from the Geoscience Australia (GA) platform (https://portal.ga.gov.au/), the structures emitting H
2 confirmed by the surface gas surveys, are characterized by the elevated pH values, thus demonstrating higher chemical reduction potential, see
Figure 20.
Figure 20. The AOI, Pingarrega Lake, pH in Calcium Chloride of the soil within: (a) 0 – 5 cm depth layer; (b) 100 – 200 cm depth layer. Colder colors represent higher values. H2 reading in ppm. Modified from GA https://portal.ga.gov.au/. The legend is available from the source.
From
Figure 20, it is also apparent that the pH values turn becoming more alkaline with depth, which correlates with the view of H
2 chemical reduction role. Contrary, closer to the surface, the system behaves as more acid, being influenced by atmospheric oxygen.
Another phenomenon of natural hydrogen interaction with soils is related to the humus degradation, followed by subsequent fertility loss. Being the aggressive chemical reduction agent, hydrogen tears long soil organic acid molecules apart, which results in forming shorter molecular chains. This effectively causes soils’ depletion/dilution, with erosion expanding rather quickly due to the decreased fertility of the humus substrate and consequent vegetation replacement by less demanding species, and/ or its further complete disappearance. From the geochemical aspect, this process correlates with iron chemical reduction from the immobile Fe3+ to the very mobile Fe2+ (see 2.2.2 Remote Sensing – ASTER), with the latter being evacuated by the surface water flows.
These processes were described in detail by Sukhanova
[55] | Sukhanova, N., Larin, N., & Kiryushin, A. (2014). Influence of endogenous hydrogen flux on chemical properties of soil. Geopolitics and Ecogeodynamics of Regions. Periodical Publication of the Taurida National University Named after V.I. Vernadsky, 10(1), 214–220. Retrieved from http://geopolitika.crimea.edu/arhiv/2014/tom10-v-1/036suzanova.pdf |
[55]
, explaining chemical relationships between the natural hydrogen degassing process and soil fertility degradation. Our discussions with the local land users describing the sequence of events in a rather similar way confirm this conceptual view.
Within the area of this study, these processes resulted in poor soil qualities and fast erosion of fertile layers, which in some cases caused the sand blows to form (see 2.2.4 Geomorphology).
2.2.9. Mineral Associations and Alterations
This dataset is useful for identification of natural hydrogen flows’ interaction with the host rocks, as well as for determining its most probable migration paths. However, mineral associations related to hydrogen metasomatism are still poorly understood.
The desk-top study of the mineral associations across the area of research was based on data available from the open sources. GeoVIEW.WA provides quite a comprehensive data set on this subject. Another set of petrology and lithology data is provided by the Western Australia Rocks (WAROX) platform, also available through GeoVIEW.WA.
Several mineralogy aspects were taken into consideration:
(i). Alkali Minerals
In particular, we would like to review the process of mineral phases’ formation with nSiO2⋅mH2O, K, Na, and Ca. It is suggested that excessive chemical elements, such as Si, Ca, Na, and K, vacate the reaction zone of hosting rocks, being assisted by the natural hydrogen degassing streams.
Additionally, iron Fe and magnesium Mg are expelled from the system. This applies primarily to pyroxenes, amphiboles, micas, etc.
Potassium K and sodium Na vacate the reaction zone in the form of soluble compounds, or alkalis (KOH and NaOH). This is why hydrogen is often associated with hyperalkaline water sources (pH > 10)
[37] | Miller, H. M., Matter, J. M., Kelemen, P., Ellison, E. T., Conrad, M. E., Fierer, N., Ruchala T., Tominaga M., Templeton, A. S. (2016). Modern water/rock reactions in Oman hyperalkaline peridotite aquifers and implications for microbial habitability. Geochimica et Cosmochimica Acta, 179, 217–241. https://doi.org/10.1016/j.gca.2016.01.033 |
[37]
. Ultimately, alkali metals end up as halite (NaCl) and sylvite (KCl) salt deposits in water streams and circular depressions along the river valleys, which quite often are tracked down as permeable zones.
The area of research presents a substantial number of examples of streams and circular depressions, sometimes referred to as playa lakes, demonstrating the abundance of halite NaCl both in water and, when dried, in surface deposits. According to the local land users, in some of the originally fresh lakes, the water turns salty within several years to several decades, as mentioned above (see 2.2.4 Geomorphology).
Calcium Ca, most likely vacating the reaction zone in the form of hydroxide Ca(OH)2, terminates its migration path nearby, depositing in the form of calcite (CaCO3) or gypsum (CaSO4·2H2O). The distribution of the latter is covered quite well on the GeoVIEW. WA ASTER layer.
Within the area of research, there are several occurrences of limestone CaCO
3, bentonite (Na, Ca)
0.33(Al, Mg)
2Si
4O
10(OH)
2·nH
2O and saponite Ca
0.25(Mg, Fe)
3((Si, Al)
4O
10)(OH)
2·n(H
2O) actively mined in the area. The example presented in
Figure 21 demonstrates the abundance of these minerals in the Pinjarrega area. The reason for this is perfectly explained by redox balances change (pH values drop) from alkaline to more acidic due to their cooling and oxygen saturation while migrating from deeper to shallow depths
.
Notably, according to the Watheroo Minerals PTY LTD geochemical assays data
, soil samples demonstrate levels of pH in the alkaline range between 8.2 and 9.4.
Figure 21. Mineral deposits and occurrences around Pingarrega Lake, AOI. Gp − gypsum, Spn − saponite, Dl − dolomite, Bn − bentonite, Ls − limestone. Mineralization locations shown in reversed magenta triangles, Company Surface Sample Geochemistry locations shown in green dots. Modified from GeoVIEW.WA https://geoview.dmp.wa.gov.au/. The legend is available from the source.
It is important to emphasize that stratigraphically, the carbonate deposits mined by Watheroo Minerals PTY LTD are located on the craton flank of the Darling Fault, therefore it would be rather difficult to link their origin to the sedimentary lithification processes such as diagenesis etc. Apparently, other mechanisms shall be suggested for these deposits’ formation processes.
(ii). Silicon (Si) Minerals
As for Silicon Si, it may migrate from the reaction zone, as we believe, in the form of polysilicic acids of the nSiO
2⋅mH
2O composition, which decompose with forming an aqueous SiO
2 gel, the further fate of which may vary from case to case. This may be explained by the following process: With a decrease in the temperature of hydrothermal solutions, normal quartz often turns into cryptocrystalline and chalcedony, and is often accompanied by the deposition of chalcedony or even opal
. Thus, depending on the conditions, the setting silica gel may turn into opals, as in Coober Pedy Opal Fields, where they are closely associated with kaolinite
[8] | Dutkiewicz, A., Landgrebe, T. C. W., & Rey, P. F. (2015). Origin of silica and fingerprinting of Australian sedimentary opals. Gondwana Research, 27(2), 786–795. https://doi.org/10.1016/J.GR.2013.10.013 |
[8]
.
In other conditions, hydrous silica gel forms layers, concretions and nodules of chert, often observed at the contact of Cretaceous and Palaeogene rocks, e.g., in the Negev Desert in Israel or on the Sinai Peninsula in Egypt. The appearance of cherts at the turn of geological epochs becomes understandable if we take into account the catastrophic nature of the planet's structure reshaping, which occurred with the active participation of hydrogen, tied with these events’ timelines.
In some cases, Si-gel vacating the hydrogen metasomatism zone crystallizes in the form of small quartz (SiO2) crystals. Sometimes the product sand consists of perfect crystals shaped as semi-rounded transparent or translucent grains of similar sizes, observed in the sand deposits.
In the area of research, Quartz and Silica layers in ASTER demonstrate abundant occurrences of these minerals, for examples in
Figure 13e and 13f, correspondingly (see
2.2.3 Remote Sensing – ASTER). Not surprisingly, there is a significant number of mining companies exploring and developing these mineral resources nearby the area of research. One of them, the Moora Mine operated by Simcoa (
Figure 22), produces silicone aggregates of the highest purity some 4 to 5 km ENE of the anomalously high soil gas H
2 reading.
Figure 22. Moora Mine, Simcoa Mines Pty Ltd (Cairn Hills, WA). Mineralization locations shown in reversed magenta triangles, Simcoa tenements shown in yellow rectangles. Modified from GeoVIEW.WA https://geoview.dmp.wa.gov.au/. The legend is available from the source.
We are still a long way from understanding the reasons why silica-gel forms quartz in some settings and chalcedony, opal or chert in others.
2.2.10. Heat Flow Studies
Outside the geothermal energy domain, the heat flow subject is not broadly discussed by the academia
and the industry. In our opinion, however, it is closely related to the natural hydrogen degassing process when viewed through the prism of the PHE concept
. According to this concept, intermetallic/silicide wedges protruding into the crust through the deep faults and rifting zones (
Figure 17) are supposed to be colder than suggested by the existing mainstream model. In this regard, the unconventionally low values of geothermal parameters for Barberton-1 well (
Figure 23) may be explained by its proximity to the Darling fault with the latter providing the cooling effect due to the presence of intermetallic silicides approaching the surface through the Proto-Darling palaeo-tectonic structure. A similar effect is observed in other parts of the world. For instance, the Baikal continental rifting system is famous for its extremely low heat flow values, resulting in permafrost zone expanding to the south for significant distances
[42] | Poort, J., & Klerkx, J. (2004). Absence of a regional surface thermal high in the Baikal rift; new insights from detailed contouring of heat flow anomalies. Tectonophysics, 383(3–4), 217–241. https://doi.org/10.1016/j.tecto.2004.03.011 |
[42]
. Another, a very well known, example of the (relatively) low heat flow value is set by Eureka Low
[65] | Williams, C. F., & Sass, J. H. (2006). Heat flow in Railroad Valley, Nevada and implications for geothermal resources in the south-central Great Basin. Geothermal Resources Council Transactions, 30, 111–116. ISSN: 0193-5933; ISBN: 0-934412-91-x |
[65]
area in Nevada, USA, where a <60 mW m
-2 to <45 mW m
-2 area is sitting right in the middle of the Great Basin province demonstrating the average values between 90 mW m
-2 and >100 mW m
-2.
Overall, data available for the bulk of the Australian continent is not too convincing
[14] | Haynes, M. W. (2021). A Bayesian Reappraisal of Australian Crustal Heat Flow and Temperature. The Australian National University (Australia). https://doi.org/10.25911/S124-AZ92 |
[14]
in terms of the mainstream model applicability.
A very comprehensive research of the Perth Basin geothermal potential done by Hot Dry Rocks
in 2008 demonstrated that the subject modeling performed through the prism of existing mainstream concept is not confirmed by the practical values received from the wells drilled in the area. Specifically, Barberton-1 well which is the closest to the Darling Fault, some 3.5km W of it, was supposed to show the highest geothermal parameters i.e., heat flow and thermal gradient, against the other wells in the Perth Basin. Instead, this well demonstrated “low geothermal gradient for the area, 1.95°C/100m. <…> The geothermal gradient for the Barberton structure compares with approximately 2.41°C/100m for Cypress Hill No.1, 2.06°C/100m for Gingin No.1, 2.37°/100m for Walyering No.l, 2.20°C/100m for Warro No.l, and 2.47°C/100m for Yallallie No.1.”
.
According to Mory and Iasky
, the thermal gradient for Barberton-1 well is even lower: 1.8°C/100m.
Barberton-1 well geothermal parameters’ comparison with other wells drilled in the Perth Basin are shown in
Figure 23.
The geothermal chart for Barberton-1 well demonstrates the extreme deviation of the actual heat flow value of 64mW/m
2 from the modelled ones, see
Figure 24. The significant number of geothermal parameter deviations from the model for the area resulted in dubbing this misfit data as “low quality” and therefore disregarding it, see p. 28 of the Hot Dry Rocks Report
.
Figure 24. Barberton-1 well heat flow depth chart. The model shown in solid red line, the actual heat flow values in green dots. From Hot Dry Rocks, 2008. https://geodocsget.dmirs.wa.gov.au/api/GeoDocsGet?filekey=1dcd69da-255b-4fef-b741-e274252c02f7-9beg4fuf54nadxivun5ih10l1ogs3wopgiti1yin
Apparently, this list of discrepancies calls for a new approach. In this regard, the PHE concept explains the majority of dilemmas and paradoxes accumulated by fundamental geoscience, which otherwise appear to remain unresolved by means of the existing mainstream model.