Recomendaciones

Early tectonic contacts within the Alpujarride complex can only be identified where the contact has juxtaposed two different rock units: the absence of grade change across these contacts mean that where the early contacts juxtapose two rock bodies of the same lithological unit, the contact is very difficult to trace. (See also Chapter 2 - section 2.5.3).

Of the four early tectonic contacts identified in the area, three of them place the graphitic schist and quartzite sequence above the non-graphitic schist and quartzite sequence (in the right-way-up limbs of the Dt generation folds). These contacts are described below. The Las Palomas contact in the south of the area juxtaposes carbonate rocks below the non-graphitic schist and quartzite sequence in the right-way-up limb of an St fold.

Regionally, the graphitic schist and quartzite sequence is generally acknowledged to underlie the non-graphitic quartzite and schist sequence, and the carbonates regionally overlie the non-graphitic phyllite and quartzite sequence (Chapter 2). The juxtapositions of the rock types generated by these early contacts suggest that reverse movement occurred along these early structures. These early contacts are likely to have formed during the crustal thickening event in the early compressional part of orogenic evolution (Chapter 1).

3.4.3.1 Rio Verde Contact

The Rio Verde Contact, well exposed in a road section of the CN340 at VF 43710666, is an example of a tectonic boundary that formed prior to or during the Ds deformation. At this location, in the north-verging (right way up) limb of a Dt fold, graphitic schists and quartzites

overlie the non-graphitic schist and quatzite sequence. This sequence is clearly non- stratigraphic, and both the graphitic and non-graphitic sequences at this locality are of kyanite-sillimanite-andalusite grade.

The Rio Verde Contact may be traced north from the locality given above, progressively passing into rocks of lower metamorphic grade. The contact cuts the Cantalobos cross- section (figure 3.4) at VF 43500694, where it is seen in the inverted (south-verging) limb of a Dt fold: here, the graphitic schist and quartzite sequence is vertically beneath (yet

structurally above) the pale schist and quartzite sequence. The rocks at both side of the Rio Verde Contact at this location are metamorphosed to gamet/staurolite-andalusite grade.

To the north of its exposure on the Cantalobos cross-section, the Rio Verde Contact intersects a stratigraphie contact (the Haza Llano boundary: Chapter 2). As a consequence of this, the trace of the Rio Verde Contact to the west is not evident (figure 2.9b).

Graphitic schists and quartzites on Morro del Cascajar (VF 43250705) overlie non-graphitic schists (figure 3.3): on the Rio Miel cross section (figure 3.2) the Cascajar body of graphitic schist is directly in contact with carbonate rocks (VF 42820697). This contact is clearly not stratigraphie, and may be attributed to the westward Continuation of the Rio Verde contact, or another early tectonic contact (figure 2.5).

3.4.3.2 El Tumbo Contact

On the Jete Road cross-section (figure 3.6), the El Cerallo stratigraphie boundary between the graphitic schist and quartzite sequence and the non-graphitic schist and quartzite

sequence is seen at VF 43900706. The thickness of non-graphitic schist seen to the north of this contact is thinned by the El Tumbo Contact (at VF 43900712): at this location, the graphitic schist and quartzite sequence is clearly placed structurally above the non-graphitic schist and quartzite sequence exposed to the south. Figure 3.24a.

The El Tumbo Contact may be distinguished further to the east, where similar contact relations to those seen on the Jete Road cross-section (figure 3.6) are identified at VF

44330723. At this location, an exposure of the non-graphitic schist and quartzite sequence is seen in the right-way-up limb of a Dt fold and exposures of the graphitic schist and quartzite sequence lie structurally above and below this exposure (figure 3.7). Further east from this

location, no exposures of the non-graphitic schist and quartzite sequence are identified, and the trace of the El Tumbo Contact cannot be discerned as the graphitic schist and quartzite sequence lies on both sides of the contact.

3.4.3.3 Molvizar Contact

Near to Molvizar (VF 44570713), in the right-way-up limb of a Dt fold, the graphitic schist and quartzite sequence is clearly seen to lie structurally above the non-graphitic schist and quartzite sequence (figure 3.24b). North of Molvizar, the traceable extent of the contact is limited as it intersects the Haza Llano stratigraphie boundary (e.g. figure 2.2): to the north of this intersection, the non-graphitic schist and quartzite sequence lies either side of the

Molvizar Contact.

Consistent contact relations may be traced to the south of this location: graphitic schists exposed in the Las Dehasas area (to the north of Salobrena) are topographically higher than the exposures of the non-graphitic quartzite and schist sequence to the east, around Lobres (VF 44950700).

Near to Motril the Molvizar Contact is clearly identified at VF 45830680: to the north of here it is displaced by syn-Ds /pre-Dt age faults (section 3.5).

3.4.3.4 Las Palomas Contact

The Las Palomas Contact is inferred from map relations. The vergence of the Dt folds (see section 3.3.3) indicates that the non-graphitic schist and quartzite sequence exposed to the north and east of the carbonate masses at Cerro Gordo (VF 43150660) and Punta de la Mona (VF 43480645) are in an overturned limb of a Dt phase fold. Late faults that have reactivated this contact clearly dip to the south: these relationships indicate that prior to brittle faulting and the Dt phase of deformation, the carbonate that now forms these two promontories lay below the non-graphitic schist and quartzite sequence. Regional relations (Chapter 2) indicate that this is contrary to the original stratigraphie configuration; consequently the contact is inferred to be due to early tectonic activity.

A reconstruction of the configuration of rocks that existed in this area, immediately after the early high-temperature episode of metamorphism and the Ds deformation event, is presented

in figure 3.25: the contacts identified on figure 2.2 are indicated on this figure.

3.5

Brittle - ductile contacts formed between Ds and Dt events

3.5.1. Introduction

The identification of brittle-ductile contacts that formed between the two phases of ductile deformation, Ds and Dt, has been achieved primarily by analysing the mineralogy and microstructure of samples on either side of the tectonic contacts. It may be expected that samples from opposite sides of a contact that formed after Ds and prior to Dt will have different early (high pressure - high temperature) metamorphic histories, but share the late (low pressure, moderate temperature) portion of the P-T evolution.