Distal deposition

The variation in Pb and Zn contents in relation to the 50% probability line between anomalous and background conditions (calculated by LDF with Pb and Zn as variables) was essentially the same at BMS No. 12, Heath Steele ACD zone and the Caribou deposit, but at Heath Steeie B zone the corresponding 50% probability line was at right angles to that at the other three deposits. Wahl (1978) concluded from these and other data that the Heath Steele B zone was a distal deposit whereas the others were proximal deposits. The major elements also define halos related to proximity to mineralization. 

Perifascicular capillaries are closer to aggregates of antibody-secreting cells (B-lymphocytes) situated in perimysial connective tissue and therefore are most severely affected by antibody-dependent cytotoxic reactions. Immune-complex deposition occurs at a higher level in the vascular tree (i.e., at arteriolar level) and this may cause fluctuations in perfusion pressure. Perifascicular capillaries are most distal from the head of vascular pressure and therefore most likely to suffer from periodic anoxia. 

Two important, unanswered questions about mesothermal gold deposits include (1) are they zoned chemically and (2) was more than one mineralizing event involved in their formation Studies of the Kolar gold field in India and the Sigma mine in Quebec found that gold fineness increased with depth. The occurrence of ankerite proximal to and calcite distal to gold veins in the HMC deposit has also been noted. 

Distal exhalative manganese enriched stratigraphy to carbonate-hosted zinc deposits, Adirondack Lowlands, New York State, U.S.A. 

Most SEDEX deposits are not precipitated directly adjacent to their feeder zone (Sangster 2002) therefore the geochemical zonation of distal products provides a valuable exploration tool. Manganese halos have been well documented for the Tynagh mine in... 

The Mn-subunit exposed in the Arnold pit contains up to 13% Mn and 13700 ppm Ba with associated elements consistent with distal hydrothermal products. Microprobe analysis determined barite to be present as inclusions within and on the margins of pyrolusite, demostrating Mn and Ba deposition from the same fluid. Such anomalous enrichments are atypical of basinal settings other than those receiving input from hydrothermal discharge. 

Sangster, D.F. 2002. The role of dense brines in the formation of vent-distal sedimentary-exhalative (SEDEX) lead-zinc deposits field and laboratory evidence. Mineraiium Deposita, 37, 149-157. 

A distal uranium halo (1 ppm) extends over 500 metres from the deposit towards surface, indicating the presence of mineralization. Significant changes in the uranium content are not observed until within approximately one hundred metres of mineralization, where partial digest uranium values begin to increase significantly. 

Anomalous values of lithium, 207pb/206pb, gpjj molybdenum (and other process-related elements) are observed within the distal uranium halo, and appear to represent intermediate and perhaps proximal halos enveloping mineralization. Local enrichments are also observed associated with structural features distal or intermediate to the main zone of mineralization, the trend of which may be useful for vectoring into the deposit. 

The Key Anacon deposits are exhalative deposits with metal zonation grading from a pyrite-chalcopyrite-pyrrhotite zone in the footwall, through a pyrite-sphalerite zone in the main parts of the deposits, to pyrite-sphalerite-galena zone in the upper and vent-distal parts of the system (cf. Petruk 2000). At the base, these deposits consist of structurally attenuated and dismembered stockwork veins and disseminations of chalcopyrite and pyrrhotite, in a matrix of chlorite. 

Jambor, J.L 1979. Mineralogical Evaluation of Proximal-Distal features in New Brunswick Massive-Sulfide Deposits. Canadian Mineralogist, 17, 649-664. 

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