scholarly journals Base-metal and REE anomalies in lower Palaeozoic sedimentary rocks of Amundsen Land, central North Greenland: implications for Zn-Pb potential

2018 ◽  
pp. 43-46
Author(s):  
Diogo Rosa ◽  
John F. Slack ◽  
Hendrik Falck
Keyword(s):  
Carbonate Rocks ◽  
Sedimentary Rocks ◽  
Mississippi Valley ◽  
Geochemical Analysis ◽  
Field Season ◽  
Lower Palaeozoic ◽  
Sedimentary Succession ◽  
Late Diagenesis ◽  
North Greenland ◽  
Mississippi Valley Type

During the 2013 field season, siliciclastic and carbonate rocks of the lower Palaeozoic sedimentary succession of the Franklinian Basin in Amundsen Land, central North Greenland, were collected for whole-rock geochemical analysis. These data are evaluated here in an attempt to identify possible hydrothermal signatures related to sediment-hosted Zn-Pb mineralisation, similar to that found in correlative strata at the large Citronen Fjord deposit located c. 100 km to the eastnorth-east. In this paper, we use the term Sedex in a broad sense to describe stratiform, sediment-hosted deposits that formed either by syngenetic (exhalative) processes or by subsea-floor replacement coeval with sedimentation (e.g. Emsbo et al. 2016); the term Mississippi Valley-type (MVT) is used for non-stratiform Zn-Pb deposits that formed epigenetically during late diagenesis or tectonism (e.g. Leach et al. 2010).

scholarly journals Precambrian–Silurian geology of the G.B. Schley Fjord region, eastern Peary Land, North Greenland

1979 ◽  
Vol 88 ◽  
pp. 63-71
Author(s):  
R.L Christie ◽  
J.R Ineson
Keyword(s):  
Sedimentary Rocks ◽  
Geological Investigation ◽  
Precambrian Rocks ◽  
Complex Region ◽  
Late Precambrian ◽  
North East ◽  
Late Palaeozoic ◽  
Field Season ◽  
Dolomite Formation ◽  
North Greenland

A structurally complex region of mainly sedimentary rocks lies north-east of the exposures of Silurian flysch in eastern Peary Land, in the vicinity of G. B. Schley Fjord (map l). South-easterly structural and sedimentary trends follow the edge of the flysch belt in a general way, so that older rocks tend to be exposed north-eastwards, towards the coast. An irregular outcrop pattern results, however, principally from numerous major and minor faults that cut the land in virtuaIly all directions. Three and possibly more geological sequences are present: (l) Precambrian rocks, comprising both sedimentary and volcanic types; (2) late Precambrian? to Silurian, beginning with a dolomite formation and ending with flysch sandstone; and (3) late Palaeozoic and younger rocks, forming part of the Wandel Sea Basin which occurs as down-faulted sedimentary outliers in the older terrains. The latter sequence is described by H~kansson, this report. Prior to the present field season, the principal geological investigation of the G. B. Schley Fjord region was that by J. C. Troelsen, a member of the Danish Peary Land Expedition (1947-1950). Troeisen (1956a) established the presence of several of the rock units discussed below. Additional remarks were published by Troelsen (1956b) and Peel, Dawes & Troelsen (1974).

scholarly journals Lower Palaeozoic stratigraphy of southern Peary Land, eastern North Greenland

1975 ◽  
Vol 75 ◽  
pp. 21-25
Author(s):  
J.S Peel ◽  
R.L Christie
Keyword(s):  
Early Cambrian ◽  
Late Precambrian ◽  
Reference Profile ◽  
The North ◽  
Field Season ◽  
Lower Palaeozoic ◽  
North Greenland

The geology of the area around Jørgen Brønlund Fjord has previously been described by Koch (1923) and Troelsen (1949, 1956), while Jepsen (1971) recently discussed the late Precambrian - early Cambrian sequence. The two month field season in 1974 was designed to complement this work by establishing a reference profile through the Lower Palaeozoic sequence exposed in the valley of Børglum Elv to the north of its outflow into Jørgen Brønlumd Fjord (fig. 5). Substantial lithological and palaeontological collections were made from approximately 2500 m of strata examined in nine stratigraphic sections.

scholarly journals Radiogenic Pb Enrichment of Mississippi Valley-Type Metallic Ore Deposits, Southern Ozarks: Constraints Based on Geochemical Studies of Source Rocks and Their Diagenetic History

Geosciences ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 172
Author(s):  
Jonathan Chick ◽  
Sydney E. McKim ◽  
Adriana Potra ◽  
Walter L. Manger ◽  
John R. Samuelsen
Keyword(s):  
Linear Trend ◽  
Ore Deposits ◽  
Source Rocks ◽  
Mississippi Valley ◽  
Isotopic Signatures ◽  
Boone Formation ◽  
Tripolitic Chert ◽  
Geochemical Studies ◽  
Mississippi Valley Type ◽  
Valley Type

Southern Ozark Mississippi Valley-type ores are enriched in radiogenic Pb, with isotopic signatures suggesting that metals were supplied by two end-member components. While the less radiogenic component appears to be derived from various shale and sandstone units, the source of the more radiogenic component has not yet been identified. Analyses of cherts from the Early Ordovician Cotter Dolomite and tripolitic chert from the Early Mississippian Boone Formation contain highly radiogenic Pb, with isotopic ratios comparable to those of ores. However, most samples have lower 208Pb/204Pb and 207Pb/204Pb for a given 206Pb/204Pb compared to ores. These relationships demonstrate that the enriched Pb isotopic values of the ore array cannot be related to the host and regional lithologies sampled, suggesting that the source of high ratios may lay further afield. The slope of the linear trend defined by the Pb isotope ratios of ores corresponds to an age of about 1.19 Ga. Therefore, an alternative for the linear array is the involvement of Precambrian basement in supplying ore Pb. Rare earth element patterns show that diagenetic processes involving the action of groundwater and hydrothermal fluids affected the sampled lithologies to various degrees, with Cotter Dolomite having experienced the highest degree of alteration.

Interpretation of Pb isotope compositions of galenas from the Midland Valley of Scotland and adjacent regions

1984 ◽  
Vol 75 (2) ◽  
pp. 85-96 ◽  
Author(s):  
John Parnell ◽  
Ian Swainbank
Keyword(s):  
Lower Devonian ◽  
Lead Isotope ◽  
Sedimentary Rocks ◽  
Isotope Ratios ◽  
Igneous Rocks ◽  
Pb Isotope ◽  
Lower Carboniferous ◽  
Granite Magma ◽  
Lower Palaeozoic ◽  
Caledonian Granite

ABSTRACTThe lead isotope compositions of 61 galenas from central and southern Scotland vary markedly between different regions. Most galenas from the southern Grampian Highlands yield isotope ratios (206Pb/204Pb 17·77 ± 0·25, 207Pb/204Pb 15·47 ± 0·05, 208Pb/204Pb 37·63 ± 0·26) less radiogenic than those from Midland Valley galenas (18·22 ± 0·12, 15·55 ± 0·05, 38·13 ± 0·14) whilst galena lead from the Southern Uplands (18·28 ± 0·12, 15·56 ± 0·03, 38·21 ± 0·18) is more radiogenic than that from the southern Midland Valley (18·12 ± 0·06, 15·52 ± 0·02, 38·06 ±0·10). The change in isotopie composition across the Highland Boundary fault reflects the presence or absence of Dalradian rocks which included a magmatic component of lead. Galenas from the Dalradian sequence in Islay, where igneous rocks are lacking, have a composition (18·14±0·04, 15·51±0·01, 37·90±0·02) more like Midland Valley galenas. In the Southern Uplands, galenas yield lead isotope ratios similar to those of feldspars from Caledonian granite (18·30 ± 0·14, 15·57 ± 0·04, 37·96 ± 0·15) analysed by Blaxland et al. (1979). The similar ratios reflect the incorporation of Lower Palaeozoic sedimentary rocks into the granite magma, rather than a granitic source for the mineralisation. The granites were then thermal-structural foci for later mineralising fluids which leached metals from the surrounding rocks. Within the Midland Valley, galenas hosted in Lower Devonian-Lower Carboniferous lavas are notably more radiogenic (18·31 ±0·12, 15·58 ± 0·06, 38·20 ± 0·16) than sediment-hosted galenas (18·14 ± 0·07, 15·52 ± 0·02, 38·08 ± 0·10). The Devonian lavas at least may have inherited lead from subducted (? Lower Palaeozoic) rock incorporated in the primary magma.

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