A report on the characterization of clay mineralogy and grain size distribution of fine-grained sediment in the Petitcodiac System

Objectives: 1) To characterize the clay mineralogy and grain size distribution of the sediments in the Petitcodiac River 2) To identify the source of the clay minerals Introduction The Petitcodiac River is located on the south east coast of New Brunswick (Fig 1). A

causeway was built approximately 22 km from the head of the tide affected the physical

and biological processes such as tidal exchange and sediment transport. The areas

downstream the causeway were sampled for clay mineralogy and grain size distribution.

Using clay mineralogy one can identify the source materials making up the

sediment and trace possible transport pathways because the river borne and marine

sediments can be distinguished. The clay minerals may be transported from the Bay of

Fundy towards the head of the estuary or they may have in situ with the river.

Observations Table 1 represents the minerals and metal ions present in various sampling areas

determined by the XRD. The most common minerals are quartz, clinochlore, muscovite

and albite.

Clinochlore Fe and Mg have strong correlations with Al (Figs 2, 3 and 5; Table 2). A stronger

correlation exists between Fe and Mg (Figs 4 and 5).

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Muscovite

The relation between Al and K is not so strong although these metal ions dominate in

these clays (Figs 6 and 7; Table 2). In Cape enrage and Petitcodiac Lake, the Al content

is very high but the K content is low (samples 4 and 10).

Albite

The correlation of Na and Al is quite strong. However, in samples 2, 6 and 8, the Na

content is low (Fig 8). Anorthite is also absent in all these samples (Tables 1and 2).

Anorthite

Where Na increases, Ca decreases in samples 7, 8 and 9 (Riverside samples). In samples

2 and 6, Anorthite and calcite are both absent (Fig 9).

Secondary metals

Most of the secondary metals behave similarly in the sampled areas. The highest

concentration of metals is present in Hilsborough and Chocolate River where else the

lowest concentration of metals is present in the Petitcodiac Lake. High concentrations are

also present in Shepody River and Riverside. High peaks of Mn and Pb are present in

Shepody Reservoir (sample 6) (Table 3; Fig 10).

Normalized metals

Li has the strongest correlation with mud compared to the other metals (Fig 11).

Moreover, most metals imitate the behaviour of Li (Fig 10). Once normalized to Li, the

highest concentrations of primary metals are present in sample 10 (Petitcodiac Lake) (Fig

12). The normalized secondary metals behave in a similar fashion with disappearance of

peaks for Mn and Pb in Shepody Reservoir (Fig 13).

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Normalized metals plotted from the Cause way to the Bay of Fundy

When the primary metals are plotted from the Cause way to the Bay of Fundy, they start

at high concentrations in the Petitcodiac Lake and remain consistent (Table 4; Fig 14) but

does not produce any effect on the normalized secondary metals (Fig 15). Boron

concentrations are very low in the Petitcodiac Lake but are high at the areas close to the

Bay of Fundy.

Grain size

Most of the sediments are fine grained. Large amount of clay are present in Hilsbrough

and Chocolate River where else large amount of silt is present in Shepody River and

Riverside. The Petitcodiac Lake has a large amount of sand and is the only area

consisting of gravel (Table 5).

Interpretation and discussion Most minerals like quartz, clinichlore, muscovite and albite are present in all study areas.

Also, most secondary minerals behave in a similar fashion throughout the Petitcodiac

system indicating that these minerals must have been transported from one source.

Clinochlore (Fe and Mg rich) is one of the most common minerals because it must

have evolved from vermiculite and smectite (Fe, Mg and Ca rich minerals). Moreover,

Al, Mg and Fe have the strongest correlation indicating that most of the Fe present is

from the clinochlore mineral and not hematite. Therefore, mineral alteration plays an

important role in the sediments of the Petitcodiac River.

The disappearance and reappearance of anorthite (Na rich) and calcite (Ca rich)

minerals is explained by chemical alteration of minerals which plays an important role in

the “wetting” of the mud cracks in Riverside and for the trends in mineralogy in the river

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system. A possible chemical explanation is that Anorthite alters to kaolinite which in turn

transforms to muscovite. During this process calcium and bicarbonate ions are formed.

The calcium ions combine with bicarbonate anions to form calcite that is responsible for

preventing the mud cracks from drying up. Another chemical explanation is that

Anorthite may have directly altered to muscovite giving out calcium and bicarbonate ions

which when combine together form calcite. Thus, anorthite and calcite are not seen

together in a single sample.

The secondary minerals are high at Hilsborough, Chocolate River and Shepody

River. The first two are very close to Moncton city and the later is at very close proximity

to the Bay of Fundy. Interestingly, Petitcodiac has the highest concentration of the

primary metals and lowest concentration of the secondary metals. The low concentrations

of secondary metals are a result of the far distance of the Petitcodiac lake from the Bay of

Fundy. The high concentrations of the primary metals are explained by the transport of

these minerals from the Bay of Fundy and building up in the Petitcodiac Lake as they

settle because of the Causeway. The large peaks of Mn and Pb in Shepody Reservoir are

explained by diagenetic remobilization of metals since these sediments are subject to

frequent wetting and drying cycles. Also, low concentrations of Boron are present in

Petitcodiac Lake but high concentrations are present in the areas at close proximity to the

Bay of Fundy.

Conclusion

The sediments of the Petitcodiac system is mostly fine grained with minerals transported

from one source (the Bay of Fundy). Chemical alteration of some minerals took place

during the transportation process.

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Appendix for tables

Table 1. Representation of metal ions in the minerals present in various sampling areas ID Study area Quartz Clinochlore Muscovite Albite Anorthite Hematite Calcite Boehmite 1 Hilsborough √ √ √ √ √ √ X X 2 Chocolate River √ √ √ √ X √ X X

3 Long marsh Creek √ √ √ √ √ √ X X

4 Cape enrage √ √ √ √ X √ √ X 5 Shepody River √ √ √ √ √ X X X

6 Shepody Reservoir √ √ √ √ X √ X √

7 Riverside √ √ √ √ √ √ X X 8 Riverside √ √ √ √ X √ √ X (wet) mudcracks 9 Riverside √ √ √ √ √ √ X X (dry) mud cracks

10 Petitcodiac Lake/ √ √ √ √ √ √ X X Causeway

Fe, Mg, Al K, Al Na, Al Ca, Na,

Al Fe Ca Al

Table 2. Representation of the primary metal ions present in the various samples. Study area Al (ppm) Na (ppm) Mg (ppm) K (ppm) Ca (ppm) Fe (ppm)

Hilsborough 47,853.33 20,840.09 15,088.87 25,993.42 6,262.30 45,018.93Chocolate River 50,040.40 17,445.65 14,392.85 26,967.27 4,975.56 42,228.09Long marsh Creek 40,907.49 21,437.40 10,553.18 19,421.63 7,695.34 29,211.76Cape enrage 40,490.12 21,145.81 10,300.93 18,283.66 11,000.73 29,359.19Shepody River 36,158.18 18,787.64 7,881.27 25,319.60 4,662.51 38,487.78Shepody Reservoir 36,715.73 7,791.73 10,312.61 22,696.42 3,613.28 39,879.90Riverside 24,101.52 14,918.24 5,429.87 11,938.66 5,761.16 17,376.18Riverside 36,902.15 9,188.58 7,946.40 13,859.60 15,348.09 24,458.30(wet) mudcracks Riverside 45,136.62 26,510.10 12,913.32 22,267.92 6,602.25 37,859.50(dry) mud cracks Petitcodiac Lake/ 58,177.81 28,176.92 10,680.73 16,738.99 21,930.66 33,039.43Causeway

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Table 3. Representation of the secondary metal ions present in the various samples. Study area Li B V Cr Mn Ni Zn Pb Co As Hilsborough 73.42 83.18 131.87 86.32 1141.04 76.89 82.92 24.33 18.30 14.81Chocolate River 75.45 73.97 124.25 82.21 1160.06 70.20 87.91 34.33 17.59 13.03Long marsh Creek 46.71 72.13 82.08 60.68 675.54 59.03 52.55 16.47 11.38 9.50 Cape enrage 43.49 71.94 79.92 58.98 709.04 70.45 54.59 10.08 11.61 8.76 Shepody River 55.50 97.21 117.59 75.91 925.72 68.33 63.14 23.35 15.51 12.45Shepody Reservoir 60.85 65.70 106.95 73.47 2652.03 38.55 88.34 39.38 17.83 11.74Riverside 21.62 32.29 42.85 33.09 445.61 38.55 32.16 10.90 6.61 5.07 Riverside 34.37 49.57 55.54 47.21 528.55 52.89 33.43 11.04 10.27 6.96 (wet) mud cracks Riverside 53.30 74.40 108.42 69.84 1011.01 65.85 65.23 20.97 14.60 13.22(dry) mud cracks Petitcodiac Lake/ 22.89 10.92 125.62 23.45 643.63 31.46 39.55 11.84 11.81 1.60 Causeway

Table 4. Primary metal ions from the Cause way to the Bay of Fundy.

ID Study area Al (ppm) Na (ppm) Mg (ppm) K (ppm) Ca (ppm) Fe (ppm) 1 Petitcodiac Lake/ 58,177.81 28,176.92 10,680.73 16,738.99 21,930.66 33,039.43 Causeway 2 Riverside 24,101.52 14,918.24 5,429.87 11,938.66 5,761.16 17,376.183 Riverside 36,902.15 9,188.58 7,946.40 13,859.60 15,348.09 24,458.30 (wet) mudcracks 4 Riverside 45,136.62 26,510.10 12,913.32 22,267.92 6,602.25 37,859.50 (dry) mud cracks 5 Hilsborough 47,853.33 20,840.09 15,088.87 25,993.42 6,262.30 45,018.936 Chocolate River 50,040.40 17,445.65 14,392.85 26,967.27 4,975.56 42,228.097 Shepody River 36,158.18 18,787.64 7,881.27 25,319.60 4,662.51 38,487.78

8 Shepody Reservoir 36,715.73 7,791.73 10,312.61 22,696.42 3,613.28 39,879.90

9 Cape enrage 40,490.12 21,145.81 10,300.93 18,283.66 11,000.73 29,359.19

10 Long marsh Creek 40,907.49 21,437.40 10,553.18 19,421.63 7,695.34 29,211.76

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Table 5. Grain size of the sediments in the Petitcodiac system. Study area Clay % Silt % Mud % Sand % Gravel %

Hilsborough 73.1 25.4 98.5 1.4 0 Chocolate River 78.5 21.3 86.83 12.95 0

Long marsh Creek 44.1 54.9 99 1 0 Cape enrage 36.75 57.2 93.95 4.42 0

Shepody River 27.2 61.8 89 12.29 0 Shepody Reservoir

Riverside 10.9 62.4 73.3 27.5 0 Riverside (wet) 24.4 72.2 96.6 6.7 0 Riverside (dry) 63.9 23.9 87.8 13.4 0

Petitcodiac Lake/ 10.03 18.18 28.21 69.44 1.44

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Appendix for figures

Fig 1. Map of the sampled areas in the Petitcodiac system, New Brunswick

Fig 2. Relation of Al and Mg in clays of the Petitcodiac River

R2 = 0.5639

02,0004,0006,0008,000

10,00012,00014,00016,000

0 10,000 20,000 30,000 40,000 50,000 60,000 70,000

Al (ppm)

Mg

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Fig 3. Relation of Al and Fe in the clays of Petitcodiac River

R2 = 0.3485

05,000

10,00015,00020,00025,00030,00035,00040,00045,00050,000

0 10,000 20,000 30,000 40,000 50,000 60,000 70,000

Al (ppm)

Fe

Fig 4. Relation of Fe and Mg in clays of Petitcodiac River

R2 = 0.6515

02,0004,0006,0008,000

10,00012,00014,00016,000

0 10,000 20,000 30,000 40,000 50,000

Fe (ppm)

Mg

Fig 5. Relation of Al, Fe and Mg in the fine-grained sediments of the Petitcodiac system.

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Fig 6. Relation of Al and K in the Petitcodiac River.

R2 = 0.1728

0

5,000

10,000

15,000

20,000

25,000

30,000

0 10,000 20,000 30,000 40,000 50,000 60,000 70,000

Al (ppm)

K

Fig 7. Relation of Al and K in the sediments of the Petitcodiac system

Fig 8. Relation of Al and Na in the Petitcodiac River.

R2 = 0.3902

0

5,000

10,000

15,000

20,000

25,000

30,000

0 10,000 20,000 30,000 40,000 50,000 60,000 70,000

Al (ppm)

Na

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Fig 9. Relation of Al, Na and Ca in the sediments of the Petitcodiac system.

Fig 10. Correlation of the secondary metals in the sediments of the Petitcodiac River.

Fig 11. Relation between Li and Mud %

R2 = 0.3178

0.0010.0020.0030.0040.0050.0060.0070.0080.00

0 20 40 60 80 100 120

Mud (%)

Li p

pm

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Fig 12. Primary metals normalized to Li in the Petitcodiac River system.

Fig 13. Secondary metals normalized to Li in the Petitcodiac River system.

Fig 14. Normalized primary metals from the Causeway to the Bay of Fundy.

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Fig 15. Normalized secondary metals from the Causeway to the Bay of Fundy.

Fig 16. Normalized Boron trend from the Causeway to the Bay of Fundy.

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