Lithogeochemistry of Geological Units in the Rachel-Laporte Lithotectonic Domain
The tables below summarize the lithogeochemical characteristics of geological units of the Rachel-Laporte lithotectonic domain. These units are described in the Geological Bulletin covering this area and in the Quebec Stratigraphic Lexicon. The 287 analyses used here are from samples collected during the Ministère’s 2009, 2011, 2012, 2015 and 2016 mapping campaigns, in addition to data from previous and assessment works. They were selected based on certain criteria, including a sum of major oxides between 97.5% and 101.2% and a loss on ignition (LOI) of <3% (except for ultramafic rock samples). Samples collected between 2012 and 2016 were analyzed by Actlabs in Ancaster, Ontario, and samples collected in 2009 and 2011 were analyzed by AcmeLabs, British Columbia.
The majority of samples in the database were analyzed for major oxides, trace elements and metals. Analyses were performed using different techniques depending on elements, such as inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma atomic emission spectrometry (ICP-AES) and neutron activation (INAA). For more information on the analysis and dissolution techniques used, refer to the information available for each sample in SIGÉOM à la carte.
Spider and rare earth element diagrams of several units and subunits are grouped together to form envelopes including analyses between the 25th and 75th percentiles of the population. This procedure was chosen to simplify the visualization of a large number of profiles or when profiles of the same unit are similar. The envelopes thus presented are therefore given as an indication.
Supracrustal Rocks
|
Stratigraphic Unit |
Classification |
Affinity |
Tectonic Setting |
Mg# |
Rare Earths |
Spider Diagram |
Comments |
|---|---|---|---|---|---|---|---|
|
Volcanic Rocks |
|||||||
|
Klein Suite (pPkle1) |
Basalt (diagram) |
Tholeiitic to transitional (diagrams) |
Plate limit basalt, N-MORB and E-MORB (diagrams) |
29.46-72.94 |
Flat profile 0.37 < (La/Yb)N < 8.89 0.38 < (La/Sm)N < 3.27 0.89 < (Gd/Yb)N < 2.66 0.64 < Eu/Eu* < 1.28 (diagram) |
Flat profile Slight negative anomalies in: Th and P Slight positive anomalies in: Nd and Ti (diagram) |
Typical composition of unaltered basalt (diagram) |
|
Stratigraphic Unit |
Classification |
Protolith and Alteration |
Mg# |
Rare Earths |
Spider Diagram |
Comments |
|---|---|---|---|---|---|---|
|
Sedimentary Rocks |
||||||
|
Secondon Suite (pPsec) |
Arkose and litharenite (diagram) |
Sedimentary rocks derived from the upper crust (granitic), weakly altered and slightly recycled (diagram) (diagram) |
32.62- 50.68 |
Profile with negative slope 22.63 < (La/Yb)N < 64.76 4.58 < (La/Sm)N < 10.17 2 < (Gd/Yb)N < 3.37 0.84 < Eu/Eu* < 1.46 (diagram) |
Profile with negative slope Negative anomalies in: Ta, Nb, P and Ti Slight positive anomaly in: Zr (diagram) |
|
|
Freneuse Suite (pPfru1) |
Wacke, litharenite and arkose (diagram) |
Sedimentary rocks derived from the upper crust (tonalitic to granodioritic), weakly altered and slightly recycled (diagram) (diagram) |
21.53-52.31 |
Profile with slight negative slope 1 < (La/Yb)N < 20.2 1.68 < (La/Sm)N < 5.93 0.46 < (Gd/Yb)N < 2.85 0.29 < Eu/Eu* < 1.39 (diagram) |
Profile with slight negative slope Negative anomalies in: Ta, Nb, P and Ti (diagram) |
|
|
Freneuse Suite (pPfru2) |
Wacke (diagram) |
Sedimentary rocks derived from the upper crust (tonalitic), weakly altered and slightly recycled (diagram) (diagram) |
39.16-45.41 |
Profile with slight negative slope 3.42 < (La/Yb)N < 6.99 2.41 < (La/Sm)N < 4.1 0.65 < (Gd/Yb)N < 1.58 0.69 < Eu/Eu* < 0.99 (diagram) |
Profile with negative slope Negative anomalies in: Ta, Nb and P Slight positive anomalies in: Nd, Zr, Hf et Tb (diagram) |
|
Intrusive Rocks
|
Stratigraphic Unit |
Classification |
Affinity |
Tectonic Setting |
Mg# |
Rare Earths |
Spider Diagram |
Comments |
|---|---|---|---|---|---|---|---|
|
Felsic and Intermediate Intrusive Rocks |
|||||||
|
Mercier Suite (pPmrc1) |
Tonalite, granite and granodiorite (diagram) |
Magnesian to ferriferous granitoid, calcic to alkaline, type I or S and hyperaluminous to metaluminous to peralkaline (diagrams) |
Volcanic arc, syncollision and post-collision granite (diagram) (diagrams) |
8.4-45.5 |
Flat profile 0.7 < (La/Yb)N < 12.33 1.71 < (La/Sm)N < 4.79 0.21 < (Gd/Yb)N < 1.72 0.06 < Eu/Eu* < 2.55 (diagram) |
Profile with slight negative slope Negative anomalies in: Zr and Ti Slight positive anomalies in: Ta, Hf, Sm, Tb, Yb and Lu (diagram) |
The variable composition and affinity suggest the presence of several different intrusions grouped within this unit. Granitoids are commonly enriched in muscovite. |
|
Mercier Suite (mrc2) |
Granite and granodiorite (diagram) |
Ferriferous granitoid, calc-alkaline, type I and hyperaluminous (diagrams) |
Volcanic arc and syncollision granite (diagram) (diagrams) |
2.85-16.38 |
Profile with negative slope 14.56 < (La/Yb)N < 115.24 4.62 < (La/Sm)N < 11.95 1.91 < (Gd/Yb)N < 3.59 0.77 < Eu/Eu* < 2.56 (diagram) |
Profile with negative slope Negative anomalies in: Ta, Nb, P and Ti Slight positive anomalies in: Yb and Lu (diagram) |
|
|
Stratigraphic Unit |
Classification |
Affinity |
Mg# |
Rare Earths |
Spider Diagram |
Comments |
|---|---|---|---|---|---|---|
|
Mafic and Ultramafic Intrusive Rocks |
||||||
|
Klein Suite (pPkle2) |
Gabbronorite, ultramafic rocks and gabbro-diorite (diagram) |
Tholeiitic (diagram) (diagram) |
71.66-85.45 |
Flat profile 0.47 < (La/Yb)N < 2.75 0.62 < (La/Sm)N < 1.96 0.72 < (Gd/Yb)N < 1.59 0.6 < Eu/Eu* < 1.23 (diagram) |
Flat profile Negative anomalies in: Nb, P and Eu Slight positive anomalies in: Ta, Hf, Sm and Ti (diagram) |
Despite a geochemical composition indicating dominant mafic rocks, the study of thin sections reveals that they are mainly peridotite and pyroxenite. |
|
Klein Suite (pPkle3)
|
Gabbro, gabbronorite, gabbro-diorite and ultramafic rocks (diagram) |
Mostly tholeiitic (diagram) (diagram) |
33.06-73.66 |
Flat profile 0.68 < (La/Yb)N < 9.08 0.71 < (La/Sm)N < 2.73 0.88 < (Gd/Yb)N < 2.26 0.83 < Eu/Eu* < 1.87 (diagram) |
Flat profile Negative anomalies in: Nb, P and Y Slight positive anomalies in: Ta, Hf, Sm, Ti and Tb (diagram) |
Despite a geochemical composition suggesting the presence of ultramafic rocks and gabbronorite, the study of thin sections indicates that it is essentially gabbro. No orthopyroxene was observed. |
References
Publications of the Government of Québec
GODET, A., VANIER, M.-A., GUILMETTE, C., LABROUSSE, L., CHARETTE, B., LAFRANCE, I. 2018. Chemins PT et style d’exhumation du Complexe de Mistinibi, Province du Churchill Sud-Est, Canada. MERN, UNIVERSITE LAVAL, SORBONNE UNIVERSITE. MB 2018-31, 32 pages.
TRÉPANIER, S. 2011. Guide pratique d’utilisation de différentes méthodes de traitement de l’altération et du métasomatisme. CONSOREM. MB 2011-13, 216 pages.
Other Publications
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GUILMETTE, C., HÉBERT, R., WANG, C., VILLENEUVE, M., 2009. Geochemistry and geochronology of the metamorphic sole underlying the Xigaze ophiolite, Yarlung Zangbo Suture Zone, south Tibet. Lithos; volume 112, pages 149-163. doi.org/10.1016/j.lithos.2009.05.027
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KEMPTON, P., HARMON, R., 1992. Oxygen isotope evidence for large-scale hybridization of the lower crust during magmatic underplating. Geochimica et Cosmochimica Acta; volume 56, pages 971-986. doi.org/10.1016/0016-7037(92)90041-G
MANIAR, P.D., PICCOLI, P.M., 1989. Tectonic discrimination of granitoids. Geological Society of America Bulletin; volume 101, pages 635-643. doi.org/10.1130/0016-7606(1989)101<0635:TDOG>2.3.CO;2
MCDONOUGH, W.F., SUN, S.S., 1995. The composition of the earth. Chemical Geology; volume 120, pages 223-253. doi.org/10.1016/0009-2541(94)00140-4
McLENNAN, S.M., HEMMING, S.R., McDANIEL, D.K., HANSON G.N., 1993. Geochemical approaches to sedimentation, provenance, and tectonics. Geological Society of America; Special Paper, volume 284, pages 21-40. doi.org/10.1130/SPE284-p21
NESBITT, H.W., 2003. Petrogenesis of siliciclastic sediments and sedimentary rocks. In Geochemistry of Sediments and Sedimentary Rocks: Evolutionary Consideration to Mineral Deposit-Forming Environments (Lentz, D.R., editor). Geological Association of Canada; volume 4, pages 39-51.
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