Data Report: Fluid Inclusion Studies of Detrital Quartz from the Newfoundland Basin, ODP Leg 210, Site 1276

Abstract

Twenty samples of siltstones and sandstones were taken from Ocean Drilling Program Site 1276 during Leg 210 for fluid inclusion studies. With the exception of one sample of vein calcite, all inclusions were in quartz grains. The results of fluid-inclusion petrology and microthermometry indicate the presence of three fluid inclusion types (Types 1, 2, and 3). Type 1 fluid inclusions are two-phase (liquid + vapor) aqueous inclusions, and Type 2 inclusions are monophase fluid inclusions (liquid or vapor). These are common in all samples and are formed either as primary isolated inclusions or as secondary inclusions as trails along annealed fractures in the grain. Type 3 fluid inclusions are threephase (liquid + vapor + solid) inclusions. Type 3 inclusions are rare and are observed as isolated inclusions or in a cluster with other types (i.e., Types 1 and 2). The predominant population throughout the different units sampled is two-phase (liquid + vapor) aqueous fluid inclusions (i.e., Type 1). The temperature of homogenization (TH) bivariate plots for Type 1 inclusions shows dominance throughout the hole of lowto medium-salinity fluids with minimum trapping temperatures between 150° and 400°C. 1Shryane, T., and Feely, M., 2007. Data report: fluid inclusion studies of detrital quartz from the Newfoundland Basin, ODP Leg 210, Site 1276. In Tucholke, B.E., Sibuet, J.-C., and Klaus, A. (Eds.), Proc. ODP, Sci. Results, 210: College Station, TX (Ocean Drilling Program), 1–21. doi:10.2973/odp.proc.sr.210.108.2007 2Geofluids Research Group, Department of Earth and Ocean Sciences, National University of Ireland, Galway, Ireland. Correspondence author: martin.feely@nuigalway.ie Initial receipt: 16 January 2006 Acceptance: 29 May 2007 Web publication: 16 July 2007 Ms 210SR-108 T. SHRYANE AND M. FEELY DATA REPORT: FLUID INCLUSION STUDIES OF DETRITAL QUARTZ 2 INTRODUCTION Two holes were drilled on the Newfoundland margin during Ocean Drilling Program Leg 210 (Tucholke, Sibuet, Klaus, et al., 2004). Twenty samples representing the sedimentary units in Hole 1276A were prepared for fluid-inclusion studies. Occurrence and distribution of the fluid inclusions in detrital quartz are shown in Figure F1, and microthermometric data are presented in Table T1. SAMPLES AND LITHOLOGIES The sedimentary succession recovered from Site 1276 consists of hemipelagic muds and clays that accumulated in a deep-sea environment. Episodic turbidites and mass-flow deposits introduced coarser grained sediments. Five lithographic units are recognized based on sediment types, mineralogy of biogenic and detrital components, and bedding style (Tucholke, Sibuet, Klaus, et al., 2004). The stratigraphic column (Fig. F1) shows the location of the fluid inclusion samples, the age of the unit, and the corresponding lithology. Unit 1 and 4 lithologies were not suitable for fluid-inclusion studies because the sample material proved to be too fissile for the preparation of double-polished wafers that are used for analysis. Unit 2 samples (210-1276A-9R-2, 34–37 cm; 10R-2, 37–40 cm; and 15R-2, 41–43 cm) are grainstones, calcareous sandstones, and marlstones of late Paleocene to middle Eocene age. Graded beds of grainstone to claystone are dominant. Petrological analysis shows that within the calcareous sandstones the clasts are dominantly biogenic with abundant foraminifers, radiolarians, and fragments of mollusks and echinoderms. The nonbiogenic fraction (>20%) includes reworked detrital quartz, mica, glauconite, feldspar, and opaque minerals. Unit 3 samples (210-1276A-17R-4, 92–95 cm; 19R-2, 102–105 cm; and 22R-1, 92–95 cm) are carbonate grainstones and siltstones. These predominantly mud-grade sediments are punctuated by episodic influxes of gravity-flow deposits showing graded units of muds, silts, and sandstones. Between these turbidity-current events, hemipelagic muds accumulated slowly in a low-energy, basin-floor type setting. This unit is of Campanian to late Paleocene age and crosses the Cretaceous/ Paleocene boundary interval. Unit 4 is Turonian–Santonian in age and is dominated by muddy sandstone and sandy mudstone. A single sample of muddy siltstone (210-1276A-27R-5, 87–90 cm) was analyzed from this unit. The thickest lithologic unit is Unit 5, which contains a high percentage of mudrock and displays turbidite sequences with debris flows and finely laminated black shales. Subunit 5A is Cenomanian to Turonian age and is composed of a number of graded bed units that were emplaced by gravity currents. Subunit 5A samples (210-1276A-30R-5, 84– 87 cm, and 34R-1, 114–117 cm) are calcareous sandstone to mudstone turbidites with minor mudrock and black shales. In Subunit 5B the percentage of mudrock increases; these Albian to Cenomanian sediments are dominantly mudrock with minor sandy turbidites and black shales. Samples 210-1276A-41R-2, 89–92 cm; 51R-1, 133–137 cm; 56R-2, 137– 142 cm; 68R-4, 19–22 cm; and 73R-2, 84–87 cm (not analyzed), are all from the minor sandstone units of Subunit 5B. Subunit 5C is Albian in age and dominantly mudrock, with minor sandy turbidite units. Sample 210-1276A-79R-CC is from a calcite vein in a siderite concretion, 3R 4R