Electron Microprobe Geochronology And Chemical Variation Of Detrital Monazite From The Lower Cretaceous Sandstones Of The Scotian Basin And The Chaswood Formation Eastern Canada

This Open File is one of a series on detrital and diagenetic mineralogy of the Lower Cretaceous rocks of the Scotian basin and their on-land equivalent, the Chaswood Formation, resulting from a collaborative program initiated in 2001 between Saint Mary's University, the Geological Survey of Canada and the Nova Scotia Department of Natural Resources. This report provides the results of dating of detrital monazite and a preliminary interpretation of the paleogeography and sediment dispersion pattern inferred from this data. It provides an essential database for a forthcoming GSC Bulletin on the Chaswood Formation.

Sediment provenance studies concern the origin, composition, transportation and deposition of detritus and therefore are an important part of understanding the links between basinal sedimentation, and hinterland tectonics and unroofing. Such studies can add value at many stages of hydrocarbon exploitation, from identifying regional-scale crustal affinities and sediment dispersal patterns during the earliest stages of exploration, to detailed correlation in producing reservoirs and understanding the impact of mineralogy on reservoir diagenesis. The volume showcases the wide variety of techniques available, using examples and applications from all aspects of sediment provenance research. The papers are organized into four sets around the following themes: • Overview: applications of provenance information in hydrocarbon reservoir sandstones • Provenance, diagenesis and reservoir quality • Provenance studies linking sediment to source • Looking forward: development of techniques and data handling This book is dedicated to the memory of Maria Mange and Robert A. Scott.

This Open File is one of a series on detrital and diagenetic mineralogy of the Lower Cretaceous rocks of the Scotian basin resulting from a collaborative program initiated in 2001 between Saint Mary's University and the Geological Survey of Canada. ...

Monazite dating of rocks in the Black Hills area has led to a better understanding of the timing of tectonic events and episodes of mineral growth. However, detailed geochronologic studies have not been done on rocks from the Homestake Iron Formation. The objective of this study was to constrain the age of mineralization by analyzing monazite in rocks of the Homestake Formation, and to relate these ages to textures and episodes of mineral growth. Thin sections were investigated that represent a range of metamorphic conditions. Monazite was identified optically and using a scanning electron microscope, then U-Th-Pb dated with the Ultrachron. X-ray chemical maps were used to identify potential domains for which chemical ages were calculated. An allanite to monazite reaction was trapped in garnet that displayed yttrium zonation, indicating exhaustion of the allanite REE source during garnet growth. The reaction yields an age of 1757 ± 30 Ma, consistent with regional D2 related to the Trans-Hudson Orogen (THO). several regional tectonic events are represented by monazite ages in this study. A ~1850 Ma age of one monazite grain may be attributed to early southern THO activity, such as collission between the Wyoming craton and Dakota block. Regional D1 and D2 ages are well-represented. The ~1775 Ma ages are associated with D1 Yavapai island-arc collision to the south of the Black Hills. Some ~1670 Ma ages may have formed during far-field Mazatzal deformation to the south of the Yavapai terrane. The ~1715 Ma ages associated with intrusion of the Harney Peak Granite are prevalent in the Black Hills are considered a minimum age for mineralization. These ages have not yet been found in the Homestake Formation. This may be due to lower temperatures during mineralization that did not intersect a stability range of monazite, which experimentally forms at low temperatures and at a higher amphibolite facies grade. Several ~1300 and ~1200 Ma ages occur in lower-grade rocks and may have formed in the low-temperature stability range of monazite during the slow cooling period of the Black Hills.