NW Section of the Tamboril-Santa Quiteria Complex, Ceara, Brazil
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This page is part II of our study of the Santa Quiteria Complex Part I. Here the focus is the area NW and W of Santa Quiteria , between the towns of Itapipoca, Amontada and Miraima. This page also documents two outcrops of the Transbrasiliano Lineament. We define the Itapipoca-Amontada structural domain that is characterized by two deformation phases, contemporaneous with water-fluxed melting and the production of hornblende leucosomes. a) D1 is characterized by N-S shear foliation with a well developed lineation plunging genlty to S-SSE. Outcrops DKE 600-602 and 605 shows D1 overprinted to different degrees by D2. In these, S1 dips to the west and the movement combines dextral and normal components. Elsewhere, S1 dips to the east and has a similar lineation but the movement sense combines dextral and reverse components DKE 606 and 609). These define large scale folds plunging south. Within S1 there are isoclinal folds. Rocks typically have undergone anatexis and leucosomes contain Hbl and Bt and lack anhydrous pertitectic phases. b) D2 is characterized by folds and thrusts with a small dextral component. It overprints D1 and is characterized by asymmetric upright plunging folds trending NE-SW. These are commonly small scale folds (50cm scale) associated with axial planar leucosomes with Hbl or Bt and lacking anhydrous peritectic minerals. c) Overprinting of D1 by D2 gives rise to small scale domes and basins. We also define the Forquilha-Miraima structural domain characterized by normal movement to E and ESE on shallow dipping foliations. The conclusion in Part I that the core area of the Santa Quiteria pluton went down in relation to its surroundings during a generalized extension is further supported here.
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| 1a) Geological Map of the Santa Quiteria granite in red and surroundings with hand written field stations. |
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| 1b) D1 fold in 3D showing the strong lineation parallel to axis. Lax=Lx=180/18, S1 axial plane N-S/60-80E. | 1c) F1 folds plunging S, photo looking S at low angle to fold axis creating an exagerated pattern. |
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| 1d) Steep wall showing D2 asymmetric folds N50E/60W, with a thrusting component. | 1e) Tighter version of D2 folds (steep wall). |
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1f) Vertical wall with a D2 thrust plane with leucosome. | 1h) same as f. |
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1i) Horizontal plane showing dextral component on D2 thrust plane and interference pattern with south plunging F1 folds, forming domes and basins. | 1j) Inclined wall showing interference pattern between F1 gently south plunging folds and drag folds on the margins of S2 dextral-thrust. |
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1k) domes and basins forming complex patterns. This was interpreted as a result of D1 sheath folds as there is no evidence of a D2 thrust plane in the immediate vicinity. |
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| 2a) Hbl leucosomes sheared into sigma clasts: dextral movement on shear plane related to D1, nearly horizontal plane parallel to Lx | 2b) Same as previous, notice asymmetric fold with vergence to the right. Notice also two sigma shaped Hbl grains left of the lens cap. |
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| 2c) Same as above, Hbl grains sheared into sigma clasts indicative of dextral movement. | 2d) Long limb of F1 showing parasitic asymmetric folds in leucosome with vergence to the right: dextral shearing. |
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2e) F2 folds treniding NE-SW causing undulations of S1 at metre scale. | 2f) Deatail of previous one showing an F1 closure on the hinge of F2.. |
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2g) F1 isoclinal fold refolded by F2. |
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| 3a) Broad D2 hinge zone, plunging gently SW (245-250), with the envoltoria trending 340. Layer with few leucosomes, has few and low amplitude folds. Layers with lots of melt have high amplitude folds (close to down plunge view). Notice axial planar leucosomes. | 3b) Asymmetric F2 folds with vergence to the left (south). This fold style is typical of F2 (see Figs 1d-1e above). Looking down plunge to SW on subhorizontal plane. |
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| 3c) Partial and chaotic transposition of pre-existing stromata by S2 axial plane filled with leucosome. | 3d) More advanced transposition of pre-exisitng foliation (S1) into S2. |
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| 4a) Two stretching lineations: 110 (parallel to the length of the photograph) and 60 (oblique to the photograph). Foliation parallel plane dipping gently east (right). | 4b) Normal movement parallel to Lx=110. Vertical wall. |
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| 4c) Normal movement parallel to Lx=110. Vertical wall. | 4d) Disruption of psammites into mobile pelitic layers. The whole package is isoclinally folded (with rootless folds of psammite blocks) within the gently E-dipping foliation. This foliation is also gently folded defining upright, south-plunging folds. |
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| 5a) Mylonitic Part of the Transbrasiliano Lineament. | 5b) zoom in. |