Abstract The Bathurst Mining Camp is made up of several different tectonic blocks and slivers—the Fournier, California Lake, Tetagouche, and Sheephouse Brook blocks and the blueschist and Bamford Brook slivers. These blocks and slivers are characterized by unique Arenig-Caradoc volcanic stratigraphies, indicating they represent widely separated, ensialic to ensimatic portions of the Tetagouche-Exploits back-arc basin. Their structural juxtaposition took place during the Ashgill-Ludlow closure of the Tetagouche-Exploits back-arc basin. The Tetagouche-Exploits back-arc basin formed in response to rifting of the northwest-facing Popelogan arc, although the extension-rifting history was diachronous and involved multiple stages. The rifting responsible for the California Lake block (ca. 472–468 Ma) took place before the rifting of the Tetagouche (ca. 467–465 Ma) and Sheephouse Brook blocks (ca. 466–464 Ma). These three blocks have ensialic to transitional crust and share a similar pre-Arenig basement consisting of Miramichi Group deep-water sandstones and shales. Oceanic to transitional back-arc crust is preserved in the Fournier block and the blueschist and Bamford Brook slivers. The various blocks and slivers were sequentially incorporated into the Brunswick subduction complex during closure of the back-arc basin. Massive sulfide deposits in the Brunswick mining camp mainly occur in the California Lake, Tetagouche, and Sheephouse Brook blocks. Radiometric age dating indicates that massive sulfide deposition took place during a protracted period of ca. 12 m.y., although occurring at different intervals in each block. High heat flow due to extension and/or rifting of the Popelogan arc combined with anoxic bottom conditions in the associated basins seem to be a prerequisite for formation of the large massive sulfide deposits. The oldest known massive sulfides are hosted by early Arenig (ca. 478 Ma) dacites of the Clearwater Stream Formation of the Sheephouse Brook Group, which may represent the earliest stages of extension of the Popelogan arc. The main massive sulfide bodies in the California Lake Group are represented by the middle to upper Arenig (ca. 472–470 Ma) Caribou-type deposits, whose formation coincides with the early stages of rifting of the California Lake block from the Popelogan arc. The large, massive sulfide deposits in the Tetagouche Group (referred to as the Brunswick-type deposits) are typically hosted by, or intimately associated with, the pyroclastic and tuffaceous sedimentary rocks that occur near or at the top of the Nepisiguit Falls Formation (ca. 469–468 Ma). The Brunswick-type deposits formed during extension rather than rifting of the Tetagouche block from the Popelogan arc, because mafic volcanism does not accompany felsic volcanism in the Nepisiguit Falls Formation. Rifting-related mafic volcanism becomes abundant in the overlying Flat Landing Brook Formation (ca. 467–465 Ma), the rhyolites of which host a few small massive sulfide deposits. Some contemporaneous massive sulfide mineralization occurs also in the coeval feldspar-porphyritic rhyolites of the Sheephouse Brook Group.

Abstract The Lichfield Permo-Triassic Sandstone aquifer is a strategic groundwater resource for the UK West Midlands. However, the flows of a number of streams have been heavily affected by abstraction. The catchment of one of these, the Leamonsley Brook, is under-drained by the Hanch Tunnel, a 5 km-long water transfer tunnel that is more than 150 years old. The Hanch Tunnel was excavated below the water-table for its entire length and is only partly lined. Regional-scale simulation of the aquifer was undertaken using a version of the USGS MODBRNCH code, which had been previously adapted to enable simulation of both open channel and pressurized pipe flow systems (the ‘Adit Code’). This paper reports on the simulation of the Hanch Tunnel, with an emphasis on the representation of this tunnel, and its effects on the groundwater flow in the Leamonsley Brook catchment. Critical aspects to consider when implementing the Adit Code are identified and discussed. The value of the application of the Adit Code for options appraisal to resolve the low-flow conditions of the Leamonsley Brook is explored.

Abstract In 1995, a helicopter-borne geophysical survey combining magnetic, electromagnetic, and gamma ray spectrometric sensors was flown over the entire Bathurst Mining Camp, northeastern New Brunswick. In 1997, field studies under the EXTECH II program were conducted in selected areas throughout the Bathurst Mining Camp to evaluate the gamma ray spectrometric component of that survey. Herein, we describe results from 776 in situ K, equivalent uranium (eU) and equivalent thorium (eTh) abundance spectrometric readings and relate these to the airborne data and the most recent geological and geochemical knowledge of the Bathurst Mining Camp. Although there is considerable overlap in regional radioactive element signatures, distinctive trends are apparent within and between the felsic volcanic and volcaniclastic rocks of the various formations within the three geological groups surveyed (Tetagouche, California Lake, and Sheephouse Brook). These trends are largely due to different responses reflecting primary litho-geochemical variations and subsequent seawater hydrothermal alteration and/or greenschist metamorphic overprints. These trends are well supported by lithogeochemical data and were used to revise the bedrock geologic maps in several areas. Alkali element mobility attendant with hydrothermal alteration and metamorphism complicates interpretation of the potassium data, but good correlations between immobile, high field strength elements and thorium abundances illustrate the relevance and application of the gamma ray spectrometric eTh data in chemostratigraphic interpretation. Where chloritic hydrothermal alteration associated with sulfide mineralization (e.g., Brunswick 6, Halfmile Lake, Heath Steele, Restigouche, West Branch Forty-four Mile Brook, Devils Elbow, and Chester deposits) has mobilized certain elements, potassium depletion or enrichment can be readily quantified using in situ spectrometry. The airborne magnetic and electromagnetic patterns provide direct exploration vectors to volcanic-hosted massive sulfide mineralization, but the gamma ray spectrometric patterns generally do not. This is because the technique does not detect the massive sulfides directly but rather the effects of alteration associated with some of the deposits. Further, K commonly behaves conservatively under the mild to moderately intense hydrothermal alteration effects typically observed at most of the deposits. The presence of overburden and host-rock cover in areas of nonoutcropping mineralization also reduces the effectiveness of gamma ray spectrometry in exploration. However, the presence of hydrothermally altered rocks present in outcrop or overburden at a few deposits coincides with subtle variation in the local airborne patterns, and these may be useful in the exploration for concealed mineralization at the deposit or property scales.