New methods in provenance studies based on heavy minerals: an example from Miocene sands in Jylland, Denmark

Abstract

New techniques using Computer Controlled Scanning Electron Microscopy (CCSEM) and Laser Ablation -Inductively Coupled Plasma -Mass Spectroscopy (LA-ICP-MS) have recently been developed at the Geological Survey of Denmark and Greenland (GEUS) to determine source, compositional variation and sedimentary pathways of sandstones. These new time-and cost-efficient methods are highly applicable in petroleum and mineral exploration. This paper illustrates how the provenance and variability of Miocene titanium-rich sands in western and central Jylland have been investigated, but the methods are presently also used offshore the Faroe Islands and in East and West Greenland.CCSEM and LA-ICP-MS utilise simple sample preparation methods, are relatively rapid and less expensive than conventional methods and yield more information. Heavy mineral (titanium) exploration techniquesExploration for economic concentrations of valuable heavy minerals, particularly Ti-bearing minerals, necessitates knowledge of their compositional variation and the sand transport processes into the sedimentary basin where they are found (Morton & Hallsworth 1999;Morton et al. 2004). Conventional provenance studies employ methods such as Sensitive High Resolution Ion MicroProbe (SHRIMP) and Electron MicroProbe Analysis (EMPA) that require time-consuming and often tedious sample preparation, are thus expensive, and are therefore not suitable as a standard exploration technique. As part of a provenance study of ilmenite-rich sands occurring in the Miocene of western Denmark carried out at GEUS, it was the aim to develop a more cost-efficient standard analytical tool that could integrate bulk rock chemostratigraphic data, mineral compositional data and age information. This study describes the use of CCSEM and LA-ICP-MS as alternative techniques, capable of providing detailed information relevant to sand provenance more rapidly and less expensively than conventional methods. General geological settingThe coastline of the proto-North Sea had a NW-SE trend across central Jylland during the Miocene (Fig. 1). The coastal regions were sourced by large rivers draining the western part of the Scandinavian shield during the early Miocene. A distinct change to a more westerly transport direction occur-

Lithostratigraphy of the Upper Oligocene – Miocene succession of Denmark

“…History. Knudsen et al (2005) recognised that fine-grained sand layers with a high content of heavy minerals occurred in the Arnum Formation in a number of boreholes in south and central Jylland; these sand layers were informally referred to as the 'Stauning Sand'. On gamma-ray logs, the sand beds are characterised by extremely high gamma-ray values.…”

“…Associated studies, for example of the climatic conditions (Larsson et al 2006;Larsson-Lindgren 2009;T. Utescher, personal communication 2009) and sediment provenance (Knudsen et al 2005;Olivarius 2009), have further added to the understanding of the depositional system.…”

Detailed mapping of marine erosional surfaces and the geometry of clinoforms on seismic data: a tool to identify the thickest reservoir sand

“…Apatite ¢ssion track data indicate initial uplift of present-day Norway at the end of the Oligocene (Japsen et al, 2007). Heavy mineral studies of lower Miocene sediments show that present-day Norway and western central Sweden formed the source area for the studied succession (Knudsen et al, 2005;Olivarius, 2008). As a consequence of the increased relief in the hinterland and the relatively high precipitation, ca.…”

Distinguishing fluvio‐deltaic facies by bulk geochemistry and heavy minerals: an example from the Miocene of Denmark

“…1) and are treated here together as the Odderup unit. The Stauning sand is dominated by fine-grained sand deposited at water depths of 10 to 15 m on the shoreface, while the Odderup sand was deposited on the foreshore (Knudsen et al, 2005). The Odderup unit constitutes a dominantly aggrading succession, where even the foreshore deposits were preserved due to a steadily rising eustatic sealevel and subsidence in the North Sea Basin.…”

“…The ultimate aim is to utilize chemical and mineralogical variations up through a borehole in order to differentiate specific facies in the absence of additional data. The recently developed computer-controlled scanning electron microscopy (CCSEM) method (Knudsen et al, 2005;Keulen et al, 2008), first described by Knudsen (1998), has helped in characterizing the facies, thereby validating this new application of the method.…”