Marine heat flow measurement

Fang, Changle (1985) Marine heat flow measurement. Doctoral (PhD) thesis, Memorial University of Newfoundland.

[English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (29MB) [English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. (Original Version)

Abstract

Heat flow out of the Earth and the temperature field at depth are determined by the heat sources in the Earth, thermal history of the Earth and tectonic processes. Heat flow studies also provide a useful tool for understanding crustal and lithospheric structures and the nature of their evolution. Global and regional heat flow studies involve both continental and oceanic experiments. This thesis mainly describes the design, construction and deployment of a microprocessor controlled marine heat flow probe. -- Some shortcomings exist in the previous prototypes of sea floor heat flow instruments. They are: inflexibility in their operational parameters; uneconomical use of data storage; vulnerability to stochastic error; lack of communication between instrument and ship; low sensitivity and no real-time information on the records. For heat flow data processing, a software package is desired to allow real-time, interactive reduction using an on-board computer. -- The newly designed instrument overcomes these shortcomings by means of the following improvements: -- (1) Microprocessor control. The instrument contains a microcomputer which can be used not only to control and re-allocate parameters of the heat flow probe according to ambient conditions but also as a computer for data processing. -- (2) Data storage. Only the data which are related to thermal gradient and in situ thermal conductivity measurements are stored. Other data, such as those recorded when ship moves to next station, are discarded automatically (but transmitted and kept on the disks of on-ship computer). -- (3) Stochastic error. High resolution data acquisition circuits are employed. Any data recorded are the average of eight measurements. This substantially increases the accuracy and stability of the data. -- (4) Communication with ship. Digital acoustic linkage of the data and operating messages between the instrument and the ship is achieved by use of a transducer, modem and the microcomputer's standard RS 232C port. -- (5) Keeping real time information. -- (6) Large working temperature range without hardware adjustment. -- The methods of producing reliable geothermal values from the probe data are discussed. A software package is developed to achieve high efficiency. The influences of sedimentation rate, topography, and bottom water temperature transients are considered. -- Two sites in offshore Atlantic Canada, namely the inlets of the south coast of Newfoundland and the Labrador Sea and Shelf, were chosen to test the newly designed heat flow probe. An interpretation of the data from these sites in terms of specific geological and geophysical crustal problems has been attempted. The heat flow values in the inlets of the south coast of Newfoundland are consistent with their counterparts on land, whereas the values in the Labrador Sea indicate a thermal regime that is abnormal compared with other geophysical evidence.

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