TY - BOOK

T1 - Alteration of subsurface basaltic rocks and glasses

T2 - implications of environmental, chemical and structural properties on Fe mobilization

AU - Stranghöner, Marius

PY - 2019

Y1 - 2019

N2 - Weathering of basaltic rocks and glasses plays a key role for the transport and geochemical cycling of elements between lithosphere and hydrosphere. Despite the vast number of scientific literature devoted to shed light on the complex mechanisms governing the alteration of silicate rocks and glasses and their significance for biotic and abiotic processes, some questions still remain unanswered. Within this dissertation the importance of volcanic islands for a potential high release of soluble Fe to ocean surface water is highlighted. It is furthermore demonstrated that microbial activity significantly contributes to the dissolution of basaltic rocks and glasses under certain environmental and substrate conditions and a strong relationship between the Fe redox state and thermal history of basaltic glasses and their dissolution behavior is emphasized. The abundance of fresh and highly reactive rocks and glasses on volcanic islands together with their exposed location and high weathering rates make them candidates for increased supply of soluble Fe to surrounding ocean surface waters. Based on a case study on the island of Hawaii differentially altered subsurface basaltic rocks of the HSDP2 ICDP drill core were characterized with respect to Fe containing solid phases and their potential Fe release. It is shown that aging of secondary Fe solid phases in subsurface basaltic rocks of Hawaii is suppressed by adsorption of dissolved Si and other anionic species preserving their high reactivity towards dissolution. Based on this observation a high release of soluble Fe from subsurface rocks of Hawaii and potentially also from other volcanic islands is expected and thought to locally impact on the primary productivity in ocean surface waters. The microbial alteration and Fe mobilization from the HSDP2 basaltic rocks was investigated using a single strain of Burkholderia fungorum as a model organism. Nutrient deficiency and attachment of microbial cells on basaltic glass surfaces promoted the microbial mediated dissolution. Moreover, quenched basaltic glasses showed increased dissolution during microbial alteration. Further investigations into the effect of thermal history on dissolution of basaltic glasses revealed that organic ligands are able to enhance in particular the dissolution of quenched basaltic glasses relative to annealed glasses of the same composition. Furthermore, it is shown that dissolution of basaltic glasses is affected by the Fe redox state and increases with increasing Fe(III) content. These findings allow for a better understanding of the relationship between the composition / structure of basaltic glasses and their dissolution behavior under certain (biotic and abiotic) environmental conditions.

AB - Weathering of basaltic rocks and glasses plays a key role for the transport and geochemical cycling of elements between lithosphere and hydrosphere. Despite the vast number of scientific literature devoted to shed light on the complex mechanisms governing the alteration of silicate rocks and glasses and their significance for biotic and abiotic processes, some questions still remain unanswered. Within this dissertation the importance of volcanic islands for a potential high release of soluble Fe to ocean surface water is highlighted. It is furthermore demonstrated that microbial activity significantly contributes to the dissolution of basaltic rocks and glasses under certain environmental and substrate conditions and a strong relationship between the Fe redox state and thermal history of basaltic glasses and their dissolution behavior is emphasized. The abundance of fresh and highly reactive rocks and glasses on volcanic islands together with their exposed location and high weathering rates make them candidates for increased supply of soluble Fe to surrounding ocean surface waters. Based on a case study on the island of Hawaii differentially altered subsurface basaltic rocks of the HSDP2 ICDP drill core were characterized with respect to Fe containing solid phases and their potential Fe release. It is shown that aging of secondary Fe solid phases in subsurface basaltic rocks of Hawaii is suppressed by adsorption of dissolved Si and other anionic species preserving their high reactivity towards dissolution. Based on this observation a high release of soluble Fe from subsurface rocks of Hawaii and potentially also from other volcanic islands is expected and thought to locally impact on the primary productivity in ocean surface waters. The microbial alteration and Fe mobilization from the HSDP2 basaltic rocks was investigated using a single strain of Burkholderia fungorum as a model organism. Nutrient deficiency and attachment of microbial cells on basaltic glass surfaces promoted the microbial mediated dissolution. Moreover, quenched basaltic glasses showed increased dissolution during microbial alteration. Further investigations into the effect of thermal history on dissolution of basaltic glasses revealed that organic ligands are able to enhance in particular the dissolution of quenched basaltic glasses relative to annealed glasses of the same composition. Furthermore, it is shown that dissolution of basaltic glasses is affected by the Fe redox state and increases with increasing Fe(III) content. These findings allow for a better understanding of the relationship between the composition / structure of basaltic glasses and their dissolution behavior under certain (biotic and abiotic) environmental conditions.

U2 - 10.15488/5156

DO - 10.15488/5156

M3 - Doctoral thesis

CY - Hannover

ER -