Heat flow and surface radioactivity at two sites in South Greenland

Sass, J.H.; Nielsen, B.L; Wollenberg, H.A.; Munroe, Robert J.

doi:10.1029/jb077i032p06435

Cited by 52 publications

(35 citation statements)

References 20 publications

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“…The radioactive heat production of the crust is modeled as showing exponential decrease with depth with a scale depth of 8 km which is a typical value for Precambrian continental lithosphere (Artemieva & Mooney, ). The values for thermal conductivity and heat production were initially based on observations (Sandiford & McLaren, ) and were further optimized by comparing our model outputs with local heat flux estimates inferred from borehole temperature profiles in this study and by previous authors (Andersen & North Greenland Ice Core Project members, ; Buchardt & Dahl‐Jensen, ; Dahl‐Jensen et al, , ; Fahnestock et al, ; Greve, ; Hansen & Langway, ; Petrunin et al, ; Sass et al, ; Weertman, ). The majority of local values were determined from the deep boreholes: GRIP, NGRIP, Camp Century, NEEM, and DYE‐3, where there are ice temperature profiles available.…”

Section: Methodsmentioning

confidence: 99%

Geothermal Heat Flux Reveals the Iceland Hotspot Track Underneath Greenland

Martos

Jordan

Catalán

et al. 2018

Geophysical Research Letters

153

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Curie depths beneath Greenland are revealed by spectral analysis of data from the World Digital Magnetic Anomaly Map 2. A thermal model of the lithosphere then provides a corresponding geothermal heat flux map. This new map exhibits significantly higher frequency but lower amplitude variation than earlier heat flux maps and provides an important boundary condition for numerical ice‐sheet models and interpretation of borehole temperature profiles. In addition, it reveals new geologically significant features. Notably, we identify a prominent quasi‐linear elevated geothermal heat flux anomaly running northwest–southeast across Greenland. We interpret this feature to be the relic of the passage of the Iceland hotspot from 80 to 50 Ma. The expected partial melting of the lithosphere and magmatic underplating or intrusion into the lower crust is compatible with models of observed satellite gravity data and recent seismic observations. Our geological interpretation has potentially significant implications for the geodynamic evolution of Greenland.

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Section: Methodsmentioning

confidence: 99%

Geothermal Heat Flux Reveals the Iceland Hotspot Track Underneath Greenland

Martos

Jordan

Catalán

et al. 2018

Geophysical Research Letters

153

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“…Indirect evidence of the character of the substratum in Ilimaussaq comes from geophysical data. Heat-flow measurements (Sass et al 1972) have shown that the agpaitic rocks constitute a surface layer with a thickness not much greater than that of the exposed agpaitic rocks. A large positive gravity anomaly is centred in the Ilimaussaq area (Blundell 1978;Forsberg & Rasmussen 1978) where there is also a large magnetic anomaly (L. Thorning, personal communication).…”

Section: Structure Of the Ilimaussaq Intrusionmentioning

confidence: 99%

The Ilímaussaq intrusion—progressive crystallization and formation of layering in an agpaitic magma

Larsen¹,

Sørensen

1987

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Agpaitic rocks form the major part of the Ilimaussaq intrusion in S Greenland. The agpaitic magma developed as the narrow top zone in a large stratified basalt-syenite magma chamber at depth. The extreme composition of the agpaitic magma is related to an unusually high crustal position of the cupola. After emplacement, the agpaitic magma developed in an essentially closed system. The magma chamber was shallow and the volatile-rich alkaline magma was light and fluid. Heat loss was mainly through the roof, and the earliest agpaitic rocks crystallized successively downwards from the roof. The magma was probably well mixed in the early stage, but there is evidence for accumulation of residual components in a layer below the roof. This accumulation of low-melting components eventually suppressed the downwards crystallization of the roof rocks. The exposed floor rocks, kakortokites and lujavrites, are younger than the roof rocks, and at this stage the magma had probably developed repeated layering. The layering in the kakortokites, with density-graded units 7 m thick repeated continuously over the whole exposed floor, can be simply explained if they formed from a layered magma by successive upwards crystallization of individual layers. The magma at this stage was nearly volatile saturated, and each layer crystallized in response to the upward loss of a certain amount of volatiles. The lujavrites conformably overlie the kakortokites and formed after a roof collapse which caused the rate of heat loss from the remaining magma to increase. The upward crystallization became faster than the upward transport of residual components, and the successive lujavrites contain more and more of these components which finally gave rise to potentially economic concentrations of U, Be and other rare elements. Finally, a hydrothermal phase was lost from the s,'stem.

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“…-72-tion, all we can state with assurance is that the high radiogenic heat production of the Stripa quartz monzonite, together with the regionally "normal" heat flow measured in the pluton, suggests that the relatively radioactive quartz monzonitic body is small; this body appears to have little if any effect on the regional heat flow. Similar circumstances were observed at the peralkalic plutons of Ilimaussaq, Greenland (Sass et al, 1972) and Pocos de Caldas, Brazil (Vitorello et al, 1980), where high radiogenic heat production is not matched by higher-than-normal heat flow.…”

Section: Variation With Depthmentioning

confidence: 50%