A NEW METHOD FOR ASSESSING THE THERMAL HISTORY OF SEDIMENTS: A CASE STUDY FROM THE EXMOUTH PLATEAU IN NORTHWESTERN AUSTRALIA.

1990 ◽  
Vol 30 (1) ◽  
pp. 364
Author(s):  
Robert Alexander ◽  
Roger Marzi ◽  
Robert I Kagi

The Jupiter-l well on the Exmouth Plateau is presented as a case study to illustrate the use of a new molecular geochemical approach to assessing thermal history. This approach involves measuring the extent to which six independent molecular processes have occurred in a sediment column. The rates at which these molecular processes occur are well known from controlled laboratory studies; by measuring the extent to which each molecular process has occurred at a number of points in the sediment column, it is possible to identify a thermal history which is consistent with these geochemical constraints and the known geology of the sediment column. In the present study, this approach revealed that the heat flow which best accounts for present day temperatures and maturity involved a comparatively low heat flow of not more than 1.1 HFU until approximately 88 Ma before present, followed by an increase to 1.3 HFU which has continued until the present day.

Author(s):  
M. Swift ◽  
R. Boyd ◽  
D. O'Brien ◽  
J. Lorenzo

2021 ◽  
Vol 2 (1) ◽  
pp. 38-43
Author(s):  
Elena A. Glukhova ◽  
Pavel I. Safronov ◽  
Lev M. Burshtein

The article presents the one-dimensional basin modeling performed in four wells to reconstruct the thermal history of deposits and reconstruct the effective values of the heat flow density.


1991 ◽  
Vol 31 (1) ◽  
pp. 325 ◽  
Author(s):  
R. Alexander ◽  
P.G. Kralert ◽  
R. Marzi ◽  
R.I. Kagi ◽  
E J. Evans

The ester content in kerogen is depleted as sediment maturation progresses in a process which has been shown to correlate with change in the carbon preference index (CPI) of the associated soluble organic matter. We have carried out accurate laboratory measurements of the kinetics of the reaction which causes ester depletion in sediments, and we show how this information can be used to assess the thermal history of sediments. Two wells were selected, Grunter-1 and Volador-1, to provide samples from the Latrobe Group in the Gippsland Basin. The CPI values were measured to assess the extent of reaction at points down each well, and these values were then used with the kinetic parameters for the ester depletion process to obtain thermal histories which are consistent with the available maturity information.This treatment enabled the heat flow from 50 Ma to the present to be assessed and it suggests that at both locations a constant low heat flow during the Gippsland stable phase was followed by a gradual increase from the beginning of the Miocene to present-day values.


2001 ◽  
Vol 126 (3-4) ◽  
pp. 211-220 ◽  
Author(s):  
Lijuan He ◽  
Kelin Wang ◽  
Liangping Xiong ◽  
Jiyang Wang

1983 ◽  
Vol 20 (1) ◽  
pp. 135-159 ◽  
Author(s):  
C. J. Yorath ◽  
R. D. Hyndman

A tectonic model for the formation, subsidence, and thermal history of Queen Charlotte Basin is developed. Based upon regional geological and geophysical data, subsidence data from offshore wells in Hecate Strait and Queen Charlotte Sound, and thermal criteria derived from present heat flow and vitrinite reflectance information, Queen Charlotte Basin is seen to have resulted from two distinct mechanisms. (1) During a period of broad regional uplift, rifting and crustal extension occurred in Queen Charlotte Sound up to about 17 Ma ago and the Queen Charlotte Islands were displaced northwards toward their present position by transcurrent motion along the Louscoone Inlet – Sandspit fault system. The rifting generated a significant thermal anomaly and a restricted deep basin as a consequence of crustal thinning and subsequent thermal cooling. (2) Beginning about 6 Ma ago, oblique underthrusting commenced along the margin, resulting in flexural uplift of the western part of the Queen Charlotte Islands and companion subsidence in Hecate Strait and Queen Charlotte Sound. The underthrusting caused rapid cooling of the old rift basins. This phase of subsidence has continued at a decreasing rate until the present.The tectonically generated subsidence in the basin has been estimated by correcting the well data for sediment compaction, paleo water depth, and sediment loading effects. At the site of the Harlequin well in the Queen Charlotte Sound rift, with the termination of extension and associated volcanism, the basin was 1500–2000 m deep and contained little sediment. Model calculations show that this depth is consistent with the estimated extension of about 70 km and a resulting crustal thinning to 8–10 km.Models for the lithosphere flexure generated by underthrusting are constrained by the geological evidence for uplift and erosion of over 5 km of material from the western portion of the Queen Charlotte Islands and the exponentially slowing subsidence to a present regional basement depth of 2 km in Hecate Strait. An excellent fit to the pre-erosion surface profile onshore and pre-Skonun basement surface offshore is obtained with a model having underthrusting on a 30° thrust at a 10 mm year−1 orthogonal component of convergence. The flexure generated by underthrusting, which is particularly well documented in the Queen Charlotte region, appears to be a feature of most subduction zones.Vitrinite reflectance data, present heat flow estimates from the wells, and thermal modelling indicate that the heat flux in Queen Charlotte Basin was much higher in the past than at present, particularly in Queen Charlotte Sound. A model is proposed with high heat flow generated by rifting prior to 17 Ma ago, followed by cooling from the underthrust oceanic lithosphere.


2019 ◽  
Vol 12 (9) ◽  
pp. 4061-4073 ◽  
Author(s):  
Elco Luijendijk

Abstract. Low-temperature thermochronology can provide records of the thermal history of the upper crust and can be a valuable tool to quantify the history of hydrothermal systems. However, existing model codes of heat flow around hydrothermal systems do not include low-temperature thermochronometer age predictions. Here I present a new model code that simulates thermal history around hydrothermal systems on geological timescales. The modelled thermal histories are used to calculate apatite (U–Th)∕He (AHe) ages, which is a thermochronometer that is sensitive to temperatures up to 70 ∘C. The modelled AHe ages can be compared to measured values in surface outcrops or borehole samples to quantify the history of hydrothermal activity. Heat flux at the land surface is based on equations of latent and sensible heat flux, which allows more realistic land surface and spring temperatures than models that use simplified boundary conditions. Instead of simulating fully coupled fluid and heat flow, the code only simulates advective and conductive heat flow, with the rate of advective fluid flux specified by the user. This relatively simple setup is computationally efficient and allows running larger numbers of models to quantify model sensitivity and uncertainty. Example case studies demonstrate the sensitivity of hot spring temperatures to the depth, width and angle of permeable fault zones, and the effect of hydrothermal activity on AHe ages in surface outcrops and at depth.


1966 ◽  
Vol 103 (3) ◽  
pp. 240-249 ◽  
Author(s):  
M. R. W. Johnson ◽  
I. W. D. Dalziel

AbstractCertain lamprophyres in Moidart exhibit at least three sets of minor structures (cleavages, lineations and small-scale folds). During the formation of the first set the lamprophyres acquired a schistose fabric: hornblende and biotite laths crystallized along the axial surfaces of tightly compressed folds. The deformation episodes recognized in the lamprophyre sheets post-date the main episodes of major and minor folding (F1-F3) that affected the surrounding Moine gneisses. The existence of a metamorphic fabric in these lamprophyres raises interesting problems—was the thermal energy required to “metamorphose” the lamprophyres derived from deformational heat, or by a heat flow from the Moine country rocks, or were the lamprophyres deformed during cooling and consolidation from the magmatic state (autothermal metamorphism) ?


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